Search

Rice (Oryza sativa L.) is a cereal crop cultivated mainly in tropical and even some subtropical countries and provides food for more than half of the world's population. Nowadays, haploid biotechnology (gynogenesis and androgenesis) is used in breeding practice as one of the tools to improve rice, preferably in vitro androgenesis. The method of in vitro cultivation of male gametophyte is one of the promising biotechnological approaches in crop breeding research, including rice. This method is based on the biological phenomenon of androgenesis - formation of haploid regenerant plant from anther and microspore cells, whose development switches from gametophytic to sporophytic pathway. However, the wide application of these technologies is limited by the existing two problems associated with the genotype-dependence of plant regeneration and formation of albino plants in many cases in in vitro male gametophyte culture of rice. The need to eliminate these restrictions has been and remains. This requires continued research in this direction to develop and optimize the technology of cultivation, pre-treatment of anthers and components of the nutrient medium, universal for all rice genotypes. This review considers a number of factors that affect the efficiency of rice androgenesis in vitro. [ABSTRACT FROM AUTHOR]

Microspore embryogenesis is an effective method of obtaining double haploid (DH) lines in only 1 year. However, the microspore embryogenesis protocol was not efficient in pakchoi. This study aimed to establish an effective microspore culture protocol in pakchoi for hybrid breeding. The embryos were obtained from three genotypes (18SY01, 18SY02, 18SY03), but the frequency of microspore embryogenesis was significantly different. Globular embryos from three genotypes were placed into a rotary shaker (50 r/min, 25 ℃) for further culture to improve microspore embryogenesis and plantlet regeneration without callus development. Shake culture not only increased the frequency of cotyledonary embryos but also accelerated microspore embryogenesis in the NLN-13 liquid medium. Moreover, the doubled haploid rates of regenerated plants for the three genotypes were above 50%. The morphological characters and plot yield of DH lines were identified, and there were significant differences between them. According to the measurement of the self-compatibility index, all the DH lines were self-incompatible. Furthermore, the hybrid combination was prepared with the selected DH lines and the pakchoi genic male sterile line GMS010 to develop excellent hybrids. This work contributes to accelerating the application of microspore embryogenesis and supplying the DH lines in pakchoi hybrid breeding. [ABSTRACT FROM AUTHOR]

Brachiaria, a genus from the Poaceae family, is largely cultivated as forage in Brazil. Among the most cultivated varieties of Brachiaria spp., B. brizantha cv. Marandu (syn. Urochloa brizantha) is of great agronomical importance due to the large areas cultivated with this species. This cultivar is apomictic and tetraploid. Sexual diploid genotype is available for this species. The difference in levels of ploidy among sexual and apomictic plants contributes to hindering Brachiaria breeding programs. The induction of haploids and double haploids is of great interest for the generation of new genotypes with potential use in intraspecific crosses. A key factor for the success of this technique is identifying adequate microspore developmental stages for efficient embryogenesis induction. Knowledge of the morphological changes during microsporogenesis and microgametogenesis and sporophytic tissues composing the anther is critical for identifying the stages in which microspores present a higher potential for embryogenic callus and somatic embryo through in vitro culture. In this work, morphological markers were associated with anther and pollen grain developmental stages, through histological analysis. Anther development was divided into 11 stages using morphological and cytological characteristics, from anther with archesporial cells to anther dehiscence. The morphological characteristics of each stage are presented. In addition, the response of stage 8 anthers to in vitro culture indicates microspores initiating somatic embryogenic pathway. [ABSTRACT FROM AUTHOR]

Isolated Microspore Culture (IMC) is an efficient method to obtain the homozygous strain; however, it is difficult to apply in ornamental kale due to its low rate of microspore embryogenesis. Histone acetylation is an important epigenetic mechanism and may affect the changes of the microspore development pathway, promoting microspore embryogenesis. Here, microspores from three cut-flower ornamental kales, namely Crane Feather Queen (CFQ), Crane Pink (CP), and Crane Bicolor (CB), were treated with the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) to induce embryogenesis. The haploid 'CFQ' microspore plantlets were doubled with colchicine. The results for 'CFQ' revealed that, the appropriate concentration of SAHA was 0.03 μM and obtained 17.27 embryos per bud. For 'CP,' the appropriate concentration of SAHA was 0.045 μM and obtained 11.19 embryos per bud. For 'CB,' the appropriate concentration of SAHA was 0.045 μM and obtained 6.10 embryos per bud. Haploid 'CFQ' microspore plantlets were treated with 75 mg/L colchicine for 7 d and the doubling rate was 41.7%. Haploid 'CFQ' plantlets were treated with 1000 mg/L colchicine by root-soaking for 4 h and the doubling rate was 64.3%. SAHA could promote microspore embryogenesis, and colchicine root soaking was more effective than adding colchicine to the medium for haploid plantlet doubling in cut-flower ornamental kale. [ABSTRACT FROM AUTHOR]

The extant plant genus Isoetes (Isoetaceae; lycophyte, quillwort) is important from an evolutionary point of view. Species of this heterosporous genus are small herbs (up to 50 centimeters) and exhibit some morphological, anatomical and embryological features of their Paleozoic arborescent lycopsid ancestors. The species Isoetes pantii produces three kinds of microspores (monolete, alete and trilete) and two types of trilete megaspores in one and the same heterosporangium. We attempt to associate these unusual functional megaspores with various Paleozoic spores described mainly from Devonian barinophytaleans such as Omniastrobus dawsonii, Barinophyton richardsonii, B. citrulliforme and Protobarinophyton pennsylvanicum. These have two kinds of spores in a sporangium and provide the first palynological evidence of heterospory at 405 Ma. The germination of microspores and megaspores and production of gametophytes within the heterosporangia of I. pantii corresponds with that of some of its Paleozoic ancestors. Retention of megaspores within heterosporangia and their germination in situ offers evidence that I. pantii exhibits the probable route of evolution of the seed habit. These observations support the hypothesis that a typical heterosporangium was the cradle for the evolution of heterospory. [ABSTRACT FROM AUTHOR]

The mitogen-activated protein kinase (MAPK) cascade is important in stress signal transduction and plant development. In the present study, we identified a rice (Oryza sativa L.) mutant with reduced fertility, Oryza sativa mitogen-activated protein kinase 6 (osmapk6), which harbored a mutated MAPK gene. Scanning and transmission electron microscopy, quantitative RT-PCR analysis, TUNEL assays, RNA in situ hybridization, longitudinal and transverse histological sectioning, and map-based cloning were performed to characterize the osmapk6 mutant. The gene OsMAPK6 was expressed throughout the plant but predominantly in the microspore mother cells, tapetal cells, and microspores in the anther sac. Compared with the wild type, the total number of microspores was reduced in the osmapk6 mutant. The formation of microspore mother cells was reduced in the osmapk6 anther sac at an early stage of anther development, which was the primary reason for the decrease in the total number of microspores. Programmed cell death of some tapetal cells was delayed in osmapk6 anthers and affected exine formation in neighboring microspores. These results suggest that OsMAPK6 plays pivotal roles in microspore mother cell formation and tapetal cell degradation. [ABSTRACT FROM AUTHOR]

Recurrent surge in demand of multipurpose peppers have positively encouraged pepper breeding community to study diverse aspects of pepper genetics, physiology, breeding and biotic stresses, however research on application of anther culture in pepper is still limited. Current study was aimed to assess the in vitro androgenic response of two prominent Bulgarian pepper varieties in five different duration times (12, 14, 16, 18 and 20 days) on incubation period and regeneration mediums containing kinetin (0.1, 0.2 and 0.3 mg L-1) and combination of zeatin (0.25 mg L-1 0.5 mg L-1) and indole acetic acid (IAA) (0.1 mg L1). Experimental results indicated specific requirements for composition of culture medium and duration time depending on genotype. Prolonged anthers incubation on induction medium had a positive effect on embryo formation and their conversion into plantlets compared to regeneration medium variants. Highest number of embryos and plant-regenerants of variety Stryama was achieved after 18 days incubation period and medium variant containing 0.1 mg L-1 kinetin. Embryo induction in variety Zlaten Medal 7 was higher after 16 days and control medium without plant growth regulators, while regeneration at 20 days also on control medium variant. [ABSTRACT FROM AUTHOR]

Doubled haploid (DH) plant production assumes significant importance for breeders not only for mapping of genes of agronomic importance but also to shorten the breeding cycle for production of new hybrids and homogenous varieties. Microspore culture is the fastest method for production of doubled haploid plants. The success of haploid production in any species is dependent on the stage at which microspores or pollens are cultured, as this stage is crucial for switch from gametophytic to embryogenic mode of development of pollen in vitro. In the present investigation, we attempted to identify visible morphological markers in the flower bud and anthers in pepper (Capsicum annuum L.) for predicting the stages of growth of the microspores contained within them. Uninucleate microspore stage has been found to be most conducive stage for induction of androgenesis in pepper. In our study, the morphological markers for this stage were found to be: (i) size of flower bud in the range of 6-7 mm; (ii) length of anther approximately 450 µm; (iii) corolla slightly longer than that of the calyx; and (iv) green anthers with purple pigmentation at the apical end. [ABSTRACT FROM AUTHOR]

Highlights • This study aimed to develop an effective method to induce embryogenesis and to regenerate kale doubled haploid plants by treatment of microspore cultures with Methylene blue, whereby the time for breeding new hybrids may be significantly shortened. • In this paper, ploidy, self-incompatibility and uniformity of DH lines were analyzed, and only showed a slightly change. • All of the genotypic groups showed a good performance, which complying with the standard of hybrid seed production. Abstract Homozygous inbreds is the most essential part in hybrids producting, while traditional breeding methods requires more than 6 years to obtain it. Isolated microspore culture (IMC) is an effective method to produce doubled haploid (DH) homozygous lines which only 2 need years to obtain homozygous inbreds. However, the high rate of death and the low frequency of embryogenesis induction still be the critical obstacles in practice application of this valuable technique. In this paper, three different treatment concentration were used to measure Methylene blue (MB) which has been added into culture medium for four genotype of kale. The results indicated that 8 nM MB at pH 5.84 can obviously promoted the rate of embryogenesis induction, While adding 10 nM MB into NLN-13 culture medium is the most optimum concentration in both genotype, more than 5-fold increased. Moreover, the addition of 8 nM and 10 nM MB significantly decreased the rate of embryos death in four genotype, especially in 'LS-F', 0.16-fold and 0.11-fold decease were showed when compared with the control, respectively. The suitable treatment concentration of MB application would increase the rates of direct plant regeneration, 10 nM is the optimum concentration in both genotype and in 'LS-B', 2.29-fold increased in rate of direct plant regeneration was observed relative to the control. The percentage of doubled haploid rates in the four genotypes were up to 45%, in 'LS-F', comparison of the doubled haploid percentage at different MB concentration showed only slightly changes. All of DH lines we gained in this paper are self-compatibility and showed highly uniformity. According to the measurement of the compatibility index, both genotype were prospective self-incompatible lines for hybrid breeding and shows a high uniformity, which will provide an effective way to accelerate the application of microspore in hybrid breeding. [ABSTRACT FROM AUTHOR]

Aim: Separation of regeneration niches may promote coexistence among closely related plant species, but there is little evidence that regeneration traits affect species ranges at broad geographical scales. We address patterns of co‐occurrence within the genus Selaginella, an ancient lineage of free‐sporing, heterosporous, vascular plants. Specifically, we ask whether differences between species in spore size are associated with the extent of overlap in their geographical ranges, a measure of opportunity for ecological interaction. Taxon: Selaginella (Selaginellaceae: Lycopodiales). Methods: We used quantile regression to examine the relationship of spore size ratios (pairwise ratios for megaspores and microspores of co‐occurring species) to the area of range overlap and to latitude for a worldwide sample of 112 Selaginella species. Phylogenetically informed tests of statistical significance were used for each percentile relationship examined in the quantile regressions. Results: Large pairwise disparities in megaspore sizes were significantly associated with large range overlap. Disparities also tended to be larger at low latitudes. Microspore size differences, in contrast, were unrelated to shared range area or latitude. Main conclusion: Megaspore size appears to affect coexistence at a broad regional scale among Selaginella species, in at least some cases. The pattern is consistent with some degree of competitive structuring of size‐related aspects of dispersal and establishment of propagules among some co‐occurring species. Habitat complexity, such as open microsites within otherwise closed and shaded vegetation, seems likely to promote reproductive niche separation and may account for the latitudinal structure in Selaginella spore sizes. [ABSTRACT FROM AUTHOR]

Main conclusion: A cell death signal is perceived and responded to by epidermal cells first before being conveyed inwards across the anther wall in male sterile Plantago lanceolata flowers.In gynodioecious plants, floral phenotype is determined by an interplay between cytoplasmic male sterility (CMS)-promoting factors and fertility-restoring genes segregating in the nuclear background. Plantago lanceolata exhibits at least four different sterilizing cytoplasms. MS1, a "brown-anther" male sterile phenotype, segregates with a CMSI cytoplasm and a non-restoring nuclear background in P. lanceolata populations. The aim of this study was to investigate the cytology of early anther development in segregating hermaphrodite and male sterile flowers sharing the same CMSI cytoplasm, and to determine if the sterility phenotype correlates with any changes to the normal pattern of programmed cell death (PCD) that occurs during anther development. Cytology shows cellular abnormalities in all four anther wall layers (epidermis, endothecium, middle layer and tapetum), the persistence and enlargement of middle layer and tapetal cells, and the failure of microspore mother cells to complete meiosis in male sterile anthers. In these anthers, apoptotic-PCD occurs earlier than in fertile anthers and is detected in all four cell layers of the anther wall before the middle layer and tapetal cells become enlarged. PCD is separated spatially and temporally within the anther wall, occurring first in epidermal cells before extending radially to cells in the inner anther wall layers. This is the first evidence of a cell death signal being perceived and responded to by epidermal cells first before being conveyed inwards across the anther wall in male sterile plants. [ABSTRACT FROM AUTHOR]

Highlights • Microspore culture is used for rapid development of doubled haploids. • Microspore culture protocol was developed for Zengcheng flowering Chinese cabbage. • Adding right VcNa concentrations to a medium improved microspore embryogenesis. • High-yield and self-incompatible DH lines were identified for breeding. Abstract Microspore culture has been implemented in breeding programs to produce doubled haploids (DH) and thus accelerate the breeding process. This study aimed to establish an efficient microspore culture protocol for Zengcheng flowering Chinese cabbage, a highly nutritious and valued vegetable, that would be suitable for heterosis breeding. Microspores of three genotypes, 17AY010, 17AY011, and 17AY012 were successfully induced to produce embryos in NLN-13 medium. Two genotypes, 17AY011 and 17AY012 were cultivated in NLN-13 medium supplemented with different concentrations (0, 0.2, 1, 5 or 25 μM) of L-ascorbic acid sodium salt (Vitamin C Sodium Salt, VcNa) to enhance microspore embryogenesis and plant regeneration without an intervening callus phase. In both genotypes, the addition of 1 μM and 0.2 μM VcNa significantly increased the frequency of embryogenesis, 6.55-fold and 10.33-fold as compared with the control, respectively. The optimum concentration of VcNa application that would improve the rates of direct plant regeneration in the two tested genotypes was 1 μM. Moreover, the doubled haploid rates of regenerated plants of the three genotypes were above 60%. Five DH lines of 17AY012 with high yield were obtained. According to the measurement of the affinity index, they were prospective self-incompatible lines for hybrid breeding. [ABSTRACT FROM AUTHOR]

Key message: A male sterile mutant was created by 60Co γ-rays of microspores isolated from Chinese cabbage DH line 'FT'. A candidate gene for the male sterile trait was identified as Bra010198.Abstract: Male sterility is used for hybrid seed production in Chinese cabbage. In this study, we derived a male sterile mutant (ftms) from Chinese cabbage DH line 'FT' by irradiating microspores with 60Co γ-rays and realized the rapid trait transformation from male fertility to sterility for creating valuable breeding materials. Genetic analysis indicated that the male sterile trait is controlled by a single recessive nuclear gene, ftms. Microspore development in mutant ftms was aborted at the tetrad stage and associated with severely retarded degeneration and vacuolation of tapetum. Using BSR-seq analysis, the candidate region for ftms was mapped on chromosome A05. A large F2 population was created, and the region was narrowed to approximately 1.7-Mb between markers Indel20 and Indel14 via linkage analysis. The recombination frequency was extremely suppressed because the region was located on the chromosome A05 centromere. Whole-genome resequencing of mutant ftms and wild-type 'FT' aligned only one nonsynonymous SNP to Bra010198; this gene is a homolog of Arabidopsis KNS4/UPEX1, which encodes a putative β-(1,3)-galactosyltransferase that controls pollen exine development. Comparative sequencing verified the SNP position on the fifth exon of Bra010198 in mutant ftms. Further genotyping revealed that the male sterile phenotype was fully co-segregated with this SNP. Quantitative real-time PCR indicated that Bra0101918 specifically expressed in stamen. The data presented herein suggested that Bra010198 is a strong candidate gene for ftms. Hence, we developed a male sterile line for potential application in breeding and expanded the knowledge about the molecular mechanism underlying male sterility in Chinese cabbage. [ABSTRACT FROM AUTHOR]

Low temperature, particularly during the reproductive stage in rice (Oryza sativa L.), leads to reduced fertility and yield and is a major constraint faced in temperate rice ecology. The floral trait anther dehiscence length has not been quantified in relation to low-temperature tolerance in rice. Two controlled-temperature glasshouse experiments evaluated 120 genotypes from BC1F6 recombinant inbred lines when exposed to low air temperature at the booting (young microspore) and flowering stages. Genotypic differences existed for spikelet sterility (SS) after low-temperature exposure at booting and flowering stages, and a significant positive correlation (R 2 = 0.22**) was found between SS of individual genotypes at booting and flowering stages. Number of dehisced anthers had the highest correlation with SS, and accounted for 58% and 44% of variation in SS with exposure to low temperature at booting and flowering, respectively. Anther dehiscence length and number of dehisced anthers were highly correlated (r = 0.90**). After low-temperature exposure at booting, pollen number in the anther as well as the pollen's capacity to germinate effectively further differentiated low-temperature-tolerant and -susceptible genotypes. Positive relationships (r = 0.56** and 0.46*) between SS in the glasshouse and in field experiments in 2015 and 2016 seasons, respectively, provided validation of the phenotypic glasshouse screening methods utilised for low-temperature tolerance in relation to target production environments. This repeatable phenotyping system in combination with improved understanding of underlying floral traits will lead to increased efficiency in breeding for low-temperature tolerance in rice. The importance of anther dehiscence contributing to low-temperature tolerance at the booting and flowering stage in rice was identified. Floral characteristics were examined in controlled temperature glasshouse experiments with strong negative relationships observed between spikelet sterility and anther dehiscence length and number of dehisced anthers. A repeatable phenotyping system was developed and in combination with increased understanding of floral traits will lead to increased efficiency in breeding for low-temperature tolerance in rice. [ABSTRACT FROM AUTHOR]

Background: The anther cuticle, which is primarily composed of lipid polymers, is crucial for pollen development and plays important roles in sexual reproduction in higher plants. However, the mechanism underlying the biosynthesis of lipid polymers in maize (Zea mays. L.) remains unclear. Results: Here, we report that the maize male-sterile mutant shrinking anther 1 (sa1), which is allelic to the classic mutant male sterile 33 (ms33), displays defective anther cuticle development and premature microspore degradation. We isolated MS33 via map-based cloning. MS33 encodes a putative glycerol-3-phosphate acyltransferase and is preferentially expressed in tapetal cells during anther development. Gas chromatography-mass spectrometry revealed a substantial reduction in wax and cutin in ms33 anthers compared to wild type. Accordingly, RNA-sequencing analysis showed that many genes involved in wax and cutin biosynthesis are differentially expressed in ms33 compared to wild type. Conclusions: Our findings suggest that MS33 may contribute to anther cuticle and microspore development by affecting lipid polyester biosynthesis in maize. [ABSTRACT FROM AUTHOR]

Main conclusion: Stress induction followed by excessive calcium influx causes multiple changes in microspores resulting in chromatin remodeling, epigenetic modifications, and removal of unwanted gametophytic components via autophagy, switching microspores towards ME.In Brassica, isolated microspores that are placed under specific external stresses can switch their default developmental pathway towards an embryogenic state. Microspore embryogenesis is a unique system that speeds up breeding programs and, in the context of developmental biology, provides an excellent tool for embryogenesis to be investigated in greater detail. The last few years have provided ample evidence that has allowed Brassica researchers to markedly increase their understanding of the molecular and sub-cellular changes underlying this process. We review recent advances in this field, focusing mainly on the perception to inductive stresses, signal transduction, molecular and structural alterations, and the involvement of programmed cell death at the onset of embryogenic induction. [ABSTRACT FROM AUTHOR]

Summary: Grasses are essential plants for ecosystem functioning. Quantifying the selective pressures that act on natural variation in grass species is therefore essential regarding biodiversity maintenance. In this study, we investigate the selection pressures that act on two distinct populations of the grass model Brachypodium distachyon without prior knowledge about the traits under selection. We took advantage of whole‐genome sequencing data produced for 44 natural accessions of B. distachyon and used complementary genome‐wide selection scans (GWSS) methods to detect genomic regions under balancing and positive selection. We show that selection is shaping genetic diversity at multiple temporal and spatial scales in this species, and affects different genomic regions across the two populations. Gene ontology annotation of candidate genes reveals that pathogens may constitute important factors of positive and balancing selection in B. distachyon. We eventually cross‐validated our results with quantitative trait locus data available for leaf‐rust resistance in this species and demonstrate that, when paired with classical trait mapping, GWSS can help pinpointing candidate genes for further molecular validation. Thanks to a near base‐perfect reference genome and the large collection of freely available natural accessions collected across its natural range, B. distachyon appears as a prime system for studies in ecology, population genomics and evolutionary biology. Significance Statement: We used genome‐wide scans of selection in the grass Brachypodium distachyon and show that biotic stress constitutes a major constraint in this system. [ABSTRACT FROM AUTHOR]

Summary: Sperm cell (SC) lineage development from the haploid microspore to SCs represents a unique biological process in which the microspore generates a larger vegetative cell (VC) and a smaller generative cell (GC) enclosed in the VC, then the GC further develops to functionally specified SCs in the VC for double fertilization. Understanding the mechanisms of SC lineage development remains a critical goal in plant biology. We isolated individual cells of the three cell types, and characterized the genome‐wide atlas of long non‐coding (lnc) RNAs and mRNAs of haploid SC lineage cells. Sperm cell lineage development involves global repression of genes for pluripotency, somatic development and metabolism following asymmetric microspore division and coordinated upregulation of GC/SC preferential genes. This process is accompanied by progressive loss of the active marks H3K4me3 and H3K9ac, and accumulation of the repressive methylation mark H3K9. The SC lineage has a higher ratio of lncRNAs to mRNAs and preferentially expresses a larger percentage of lncRNAs than does the non‐SC lineage. A co‐expression network showed that the largest set of lncRNAs in these nodes, with more than 100 links, are GC‐preferential, and a small proportion of lncRNAs co‐express with their neighboring genes. Single molecular fluorescence in situ hybridization showed that several candidate genes may be markers distinguishing the three cell types of the SC lineage. Our findings reveal the molecular programming and potential roles of lncRNAs in SC lineage development. Significance Statement: Sperm cell (SC) lineage development from the haploid microspore to the generative cell and finally SCs in angiosperms represents a unique biological process. We characterize the genome‐wide atlas of long non‐coding RNAs and mRNAs of SC lineage cells, and show global repression of somatic and metabolic genes, and activation of the generative cell‐ and SC‐preferential genes during SC lineage development. We propose that the transcriptomic switch is important for cell fate establishment and development of the SC lineage. [ABSTRACT FROM AUTHOR]

Background: Anaerobic digestion is an alternative bioprocess used to treat effluents containing toxic compounds such as phenol and p-cresol. Selection of an adequate sludge as inoculum containing an adapted microbial consortium is a relevant factor to improve the removal of these pollutants. The objective of this study is to identify the key microorganisms involved in the anaerobic digestion of phenol and p-cresol and elucidate the relevance of the bamA gene abundance (a marker gene for aromatic degraders) in the process, in order to establish new strategies for inocula selection and improve the system's performance. Results: Successive batch anaerobic digestion of phenol and p-cresol was performed using granular or suspended sludge. Granular sludge in comparison to suspended sludge showed higher degradation rates both for phenol (11.3 ± 0.7 vs 8.1 ± 1.1 mg l-1 d-1) and p-cresol (7.8 ± 0.4 vs 3.7 ± 1.0 mg l-1 d-1). After three and four re-feedings of phenol and p-cresol, respectively, the microbial structure from both sludges was clearly different from the original sludges. Anaerobic digestion of phenol and p-cresol generated an abundance increase in Syntrophorhabdus genus and bamA gene, together with hydrogenotrophic and aceticlastic archaea. Analysis of results indicates that differences in methanogenic pathways and levels of Syntrophorhabdus and bamA gene in the inocula, could be the causes of dissimilar degradation rates between each sludge. Conclusions: Syntrophorhabdus and bamA gene play relevant roles in anaerobic degradation of phenolics. Estimation of these components could serve as a fast screening tool to find the most acclimatized sludge to efficiently degrade mono-aromatic compounds. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A doubled haploid (DH) production system for wheat using a microspore culture method produced seeds and subsequently regenerated haploid wheat plants derived from the F1 plants of two wheat populations (Irena × Ksu102 and Klasic × Ksu105). 68 DH were obtained from both populations. Field trials of these DH lines were conducted over two seasons. Genotypic differences were highly significant for all agronomic traits recorded. Sets of five gene- or allele-specific PCR markers were used for identification of genes encoding high molecular weight (HMW) glutenin subunits Ax1 and Ax2* at the Glu-A1 locus, Bx7, Bx7*, By8 and By17 at the Glu-B1 locus and Dx5, Dy10 and Dy12 at the Glu-D1 locus in wheat inbred lines. The method developed for providing DH lines and subsequent molecular analysis and quality could be useful for improving bread-making quality and developing new cultivars. Abbreviations: DH: doubled haploid; HMW: high molecular weight; HMW-GS: high molecular weight glutenins subunits; MAB: marker-assisted breeding [ABSTRACT FROM AUTHOR]

In this study, we investigated the chromosome breakage caused by gametocidal (Gc) chromosome 3Ct and its interaction with the suppressor gene Igc1 (inhibitor of gametocidal gene 1) on wheat chromosome 3B. We demonstrated cytologically that patterns of 3Ct-induced chromosomal fragmentation in microspores differed from patterns observed for other Gc genes. Uninuclear microspores of the monosomic 3Ct addition line had high frequencies of micronuclei, possibly explaining its low fertility. Chromosome fragmentation was observed in prometaphase and metaphase of the first pollen mitosis in the monosomic 3Ct addition line. Patterns of chromosome fragmentation were different from those previously reported for Gc chromosomes 2S of Aegilops speltoides, 4Ssh of Ae. sharonensis and 2Ccy of Ae. cylindrica; many chromosome fragments were observed in prometaphase of the first pollen mitosis in the monosomic 3Ct addition plants. In anthers at the binuclear stage, many microspores at the uninuclear stage coexisted with normally developed microspores. [ABSTRACT FROM AUTHOR]

Gametophytic development in Arabidopsis depends on nutrients and cell wall materials from sporophytic cells. However, it is not clear whether hormones and signaling molecules from sporophytic tissues are also required for gametophytic development. Herein, we show that auxin produced by the flavin monooxygenases YUC2 and YUC6 in the sporophytic microsporocytes is essential for early stages of pollen development. The first asymmetric mitotic division (PMI) of haploid microspores is the earliest event in male gametophyte development. Microspore development in yuc2yuc6 double mutants arrests before PMI and consequently yuc2yuc6 fail to produce viable pollens. Our genetic analyses reveal that YUC2 and YUC6 act as sporophytic genes for pollen formation. We further show that ectopic production of auxin in tapetum, which provides nutrients for pollen development, fails to rescue the sterile phenotypes of yuc2yuc6. In contrast, production of auxin in either microsporocytes or microspores rescued the defects of pollen development in yuc2yuc6 double mutants. Our results demonstrate that local auxin biosynthesis in sporophytic microsporocytic cells and microspore controls male gametophyte development during the generation transition from sporophyte to male gametophyte. [ABSTRACT FROM AUTHOR]

Abstract: Heterospory was a pivotal evolutionary innovation for land plants, but it has never been clear why it evolved. We used the geographic distributions of 114 species of the heterosporous lycophyte Selaginella to explore the functional ecology of microspore and megaspore size, traits that would be correlated with many aspects of a species’ regeneration niche. We characterized habitats at a global scale using leaf area index (LAI), a measure of foliage density and thus shading, and net primary productivity (NPP), a measure of growth potential. Microspore size tends to decrease as habitat LAI and NPP increase, a trend that could be related to desiccation resistance or to filtration of wind‐borne particles by leaf surfaces. Megaspore size tends to increase among species that inhabit regions of high LAI, but there is an important interaction with NPP. This geographical pattern suggests that larger megaspores provide an establishment advantage in shaded habitats, although in open habitats, where light is less limiting, higher productivity of the environment seems to give an advantage to species with smaller megaspores. These results support previous theoretical arguments that heterospory was originally an adaptation to the increasing height and density of Devonian vegetative canopies that accompanied the diversification of vascular plants with leaves. [ABSTRACT FROM AUTHOR]

In barley, it is possible to induce embryogenesis in the haploid and uninucleate microspore to obtain a diploid plant that is perfectly homozygous. To change developmental fates in this fashion, microspores need to engage in cellular de-differentiation, interrupting the pollen formation, and restore totipotency prior to engaging in embryogenesis. In this work, we used the barley cultivar Gobernadora to characterize the transcriptome of microspores prior to (day 0) and immediately after (days 2 and 5) the application of a stress pretreatment. A deep RNA-seq analysis revealed that microspores at these three time points exhibit a transcriptome of ~14k genes, ~90% of which were shared. An expression analysis identified a total of 3,382 differentially expressed genes (DEGs); of these, 2,155 and 2,281 DEGs were respectively identified when contrasting expression at days 0 and 2 and at days 2 and 5. These define 8 expression profiles in which DEGs share a common up- or down-regulation at these time points. Up-regulation of numerous glutathione S-transferase and heat shock protein genes as well as down-regulation of ribosomal subunit protein genes was observed between days 0 and 2. The transition from microspores to developing embryos (days 2 vs. 5) was marked by the induction of transcription factor genes known to play important roles in early embryogenesis, numerous genes involved in hormone biosynthesis and plant hormonal signal transduction in addition to genes involved in secondary metabolism. This work sheds light on transcriptional changes accompanying an important developmental shift and provides candidate biomarkers for embryogenesis in barley. [ABSTRACT FROM AUTHOR]

Cabbage is the most important member of brassica vegetables grown worldwide. Development of homozygous inbreds is pre-requisite in breeding programme and precision genetic studies in this highly heterozygous crop. Doubled haploids (DHs) developed through isolated microspore culture is one of the most effective methods for rapid development of completely homozygous lines in shortest time period. We report for the first time the role of various factors like bud developmental stages, culture density, heat shock treatments and flow cytometry on efficient microspore embryogenesis and development of DH in field grown plants of white cabbage. Among the 4 genotypes, the highest viability of microspores was recorded in bud size of 4.0–4.5 mm in genotypes, Golden Acre and KTCBH-2085 and 4.5–5.0 mm in KTCBH-6621 and KTCBH-6045. In most of the genotypes, buds with highest microspore viability also contained the maximum proportion of microspores at late uni-nucleate to early bi-nucleate stage. For effective conversion of gametophytic pathway to sporophytic pathway, a temperature shock treatment of 30 °C for 48 h + 25.0 °C (Golden Acre and KTCBH-2085) and 32.5 °C for 24 h + 25.0 °C (KTCBH-6621 and KTCBH-6045) were most suitable. The microspore density of 4 × 10 4 / ml induced the maximum number of embryos per plate in genotypes, KTCBH-2085, KTCBH-6621 and KTCBH-6045, whereas, the microspore density of 6 × 10 4 / ml was found optimum in the genotype, Golden Acre. Among the different factors, bud size and microspore developmental stage were found to be the most critical in successful microspore embryogenesis in cabbage. However, it was found that genotypes, bud size, culture density and heat treatments had significant effects on microspore embryogenesis. The interaction among these factors also played significant role in microspore embryogenesis of white cabbage. Flow cytometry analysis of microspore derived plants revealed that 41.9% of the plants were spontaneously diplodized in the process of in vitro culture. Among the 221 plants analyzed, 29.0% were haploids, 10.9% were tetraploids and 16.3% were mixoploids and aneuploids. This study will be instrumental in large scale application of DH based cabbage breeding programmes and genetic studies. [ABSTRACT FROM AUTHOR]

Nine F1 hybrids produced by crossing seven tetraploid highbush blueberry cultivars with three tetraploid Vaccinium stamineum genotypes were backcrossed to an array of highbush blueberry cultivars to produce 2500 Backcross1 (BC1) seedlings. Thirty of the most vigorous BC1 plants were intercrossed in a greenhouse. Fertility of the BC1 plants was studied by examining their pollen at 250 X and by determining the number of well-developed seeds per pollinated flower after the crosses. Percent wellformed microspores averaged 62.7% for BC1 plants compared with 30.9% for their F1 hybrid parents. Fruit set percentage was high from the BC1 intercrosses, with an average of 9.29 plump seeds per pollinated flower. The 2500 BC1 seedlings in the field were highly variable in vigor, but fewer than 10% were as vigorous as the median vigor of highbush X highbush seedlings. BC1 plants in the field averaged = 1 month later ripening than highbush X highbush seedlings and berries averaged slightly smaller. Berry clusters were very loose compared with those of highbush. Berry flavor was highly variable from plant to plant, but the berries averaged less sweet and lower in acid than highbush berries. New flavor components not found in highbush seedlings were found in only a few BC1 seedlings. Fresh berries from BC1 plants made bright red juice when crushed in water, whereas berries from most highbush cultivars produced brown to yellow juice/water mixes. Although berry quality in the BC1 population averaged lower than in highbush seedlings, some plants had berry quality as high as typical cultivars. Because V. stamineum is highly drought-tolerant, cultivars bred using V. stamineum introgression could have improved upland adaptation. [ABSTRACT FROM AUTHOR]

Jasmine [ Jasminum sambac (L.) Aiton] rarely sets seed, and its poor pollen fertility significantly influences fecundity. In this study, pollen development of jasmine was investigated at an ultrastructural level, examining the dynamic changes of microspore-tetrads and tapetum and their possible effects on pollen viability. Normally developed microspores are released at the late tetrad phase, whereas the abnormal ones formed large complexes of two to five tetrads with plasmodesmata. Ultrastructural observation also revealed that sterility of some pollen grains might result from defective development of cell walls that failed to absorb their surrounding sporopollenin to form the exine. The secretory type of jasmine tapetum, the usually degenerated middle layer and thickened endothecium were confirmed during the process of pollen development. The epidermis, middle layer and endothecium exhibited no adverse effects on pollen development and dispersal. However, the asynchronous division and delayed degradation of tapetal cells resulted in abnormal development of some microspores and the formation of massulae and empty and flat pollen grains. This is the first ultrastructural characterization of pollen development in J. sambac leading to a better understanding of embryology and poor pollen fertility of this important horticultural species. [ABSTRACT FROM AUTHOR]

Copyright of Lucrari Stiintifice, Universitatea de Stiinte Agricole Si Medicina Veterinara Ion Ionescu de la Brad Iasi, Seria Horticultura is the property of University of Agricultural Sciences and Veterinary Medicine (Editura Ion Ionescu de la Brad) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Anther development in Catalpa bignonioides Walter was investigated from the sporogenous cell to the mature pollen grain stages to determine whether the pollen and anther wall development follows the basic scheme in angiosperms. In order to follow pollen ontogeny through successive stages of pollen development, anthers at different developmental stages were embedded in epon according to the usual method, and semi-thin sections, taken from the epon embedded anthers, were stained with toluidine blue for general histological observations under light microscopy. The young anther wall of C. bignonioides consists of four layers; from the exterior, the epidermis, endothecium, middle layer, and a secretory tapetum. The tapetum is dual in origin and dimorphic. Ubisch bodies were observed on the inner tangential walls of the tapetal cells. The number of the anther wall layers changes depending on the developmental stage and region of the anther. In contrast to the other anther wall layers, epidermis and endothecium layers remain intact until anthesis. Endothecial cells enlarge and develop thickenings at maturity. During microspore development, meiocytes undergo meiosis and simultaneous cytokinesis leading to the formation of permanent tetrahedral, isobilateral and rarely linear tetrads. Pollen tetrads are shed from the anther as compound pollen grains. Results of the study revealed that pollen and anther wall development in C. bignonioides follows the basic scheme in angiosperms. [ABSTRACT FROM AUTHOR]

Purpose The purpose of the paper is to separate and purify flavonoids existed in Lamiophlomis rotata (Benth.) Kudo. by macroporous adsorption resin (MAR) mixed-bed technology. Design/methodology/approach The adsorption and desorption parameters were characterized by UV-VIS spectrophotometry. The optimal MAR mixed bed was screened based on the adsorption experiments; the experiment process was investigated by the order of single, two and three MAR mixed bed separately; and the adsorption performance, which was composed by the authority of 80 per cent adsorption ratios and 20 per cent desorption ratios, was adopted to screen MAR mixed bed for flavonoids. The adsorption dynamic investigated the order of reaction first, and then the adsorption mechanism was researched further. The adsorption thermodynamic investigated the adsorption isotherm first, and then the adsorption feature was analyzed. Findings This research found that MAR mixed bed of LS-840 + LSD301 with mass ratio of m[sub LS840]:m[sub LSD301] = 3:2 was the optimized combination, and the optimal conditions of the adsorption were volume V = 50 mL, time t = 6.5 h, T = 40°C. The desorption conditions were ethanol content = 70 per cent, desorption time t = 3.0 h, T = 40°C. The adsorption dynamic experimental data fitted better to the pseudo-second-order, and the intra-particle-diffusion model was more suitable for expression of the adsorption mechanism in mesopores process, whereas the homogeneous particle-diffusion model was more suitable in microspores. The adsorption was a physical and multilayer adsorption, and the adsorption driving force was disappeared as it transferred to the fourth layer. Practical implications Find an efficient way to separate flavonoids that useful for human's health, which can not only utilize of plant resources effectively, but also make outstanding contributions to medical industry. It has very high economic and social value. Originality/value This contribution provided a new way to separate flavonoids from Lamiophlomis rotata (Benth.) Kudo. Under the optimal conditions, the adsorption rate (F) of MAR mixed bed LS-840 + LSD301 to the flavonoids was 97.81 per cent, the desorption rate (D) was 90.02 per cent and the purity of flavonoids was dramatically increased about 2.08 fold of the crude extract from 28 to 58.4 per cent, and the recovery yield of flavonoids arrived at 91.6 per cent after a circle of adsorption/desorption operation. [ABSTRACT FROM AUTHOR]

Microspores are the pre-gametophyte stage of pollen, and have proven to be a successful tissue culture material for the production of doubled haploid plants. Microspore culture has also been used as a platform for the production of transgenic plants. The use of cell-penetrating peptides (CPPs) as transfection agents in microspores has been previously demonstrated, but at low efficiencies. Here, the pH dependent adsorption of the cationic CPP Tat 2 to the sporopollenin surface of the microspore (the exine) has been explored using electrophoretic light scattering (ELS). Furthermore the adsorption of a commercially available polycationic polymer; Luviquat FC-370 (polyquaternium D-16, PQ-D16) was similarly measured using ELS. It was found that a suspension media with a pH less than 7.0 showed an approximately ten fold decrease in the amount of Tat 2 that was required before apparent surface neutralization. This data suggests that a change in the surface chemistry of the microspore occurs in acidic pH conditions, that modulates the binding affinity of the CPP Tat 2 in a non-trivially complex manner. [ABSTRACT FROM AUTHOR]

The distribution and relative amounts of six genera of lycophyte microspores, Lycospora , Densosporites , Crassispora , Cirratriradites , Endosporites and Cadiospora , are compared in the Pennsylvanian coals from the Dobrudzha and Forest of Dean coalfields, clastic sediments from the Glace Bay borehole in the Cape Breton Coalfield, and the southern crop of the South Wales coalfield. Inverse relationships are shown between Lycospora and Densosporites and between Lycospora and Crassispora in samples from all of the coalfields. The changes in microspore assemblages suggest there were at least five different communities of lycophyte plants growing in the Pennsylvanian swamps. Changes in microspore assemblages at the Asturian/Cantabrian boundary mirror the previously described macrofloral changes at this time. [ABSTRACT FROM AUTHOR]

Calcium is widely known to have a role as a signaling molecule in many different processes, including stress response and activation of the embryogenic program. However, there are no direct clues about calcium levels during microspore embryogenesis, an experimental process that combines a developmental switch toward embryogenesis and the simultaneous application of different stressing factors. In this work, we used FluoForte, a calcium-specific fluorescent vital dye, to track by confocal microscopy the changes in levels and subcellular distribution of calcium in living rapeseed (B. napus) and eggplant (S. melongena) microspores and pollen grains during in vivo development, as well as during the first stages of in vitro-induced microspore embryogenesis in rapeseed. During in vivo development, a clear peak of cytosolic Ca2+ was observed in rapeseed vacuolate microspores and young pollen grains, the stages more suitable for embryogenesis induction. However, the Ca2+ levels observed in eggplant were dramatically lower than in rapeseed. Just after in vitro induction, Ca2+ levels increased specifically in rapeseed embryogenic microspores at levels dramatically higher than during in vivo development. The increase was observed in the cytosol, but predominantly in vacuoles. Non-embryogenic forms such as callus-like and pollen-like structures presented remarkably different calcium patterns. After the heat shock-based inductive treatment, Ca2+ levels progressively decreased in all cases. Together, our results reveal unique calcium dynamics in in vivo rapeseed microspores, as well as in those reprogrammed to in vitro embryogenesis, establishing a link between changes in Ca2+ level and subcellular distribution, and microspore embryogenesis. [ABSTRACT FROM AUTHOR]

The electrochemical corrosion behavior of a silver-plated circuit board (PCB-ImAg) in a polluted marine atmosphere environment (Qingdao in China) is studied through a simulated experiment. The morphologies of PCB-ImAg show some micropores on the surface that act as the corrosion-active points in the tests. Cl- mainly induces microporous corrosion, whereas SO2 causes general corrosion. Notably, the silver color changes significantly under SO2 influence. EIS results show that the initial charge transfer resistance in the test containing SO2 and Cl- is 9.847 × 10³, while it is 3.701 × 104 in the test containing Cl- only, which demonstrates that corrosion accelerates in a mixed atmosphere. Polarization curves further show that corrosion potential is lower in mixed solutions (between -0.397 V SCE and -0.214 V SCE) than it in the solution containing Cl- only (-0.168 V SCE), indicating that corrosion tendency increases with increased HSO3- concentration. [ABSTRACT FROM AUTHOR]

The Arabidopsis GASA10 gene encodes a GAST1-like (Gibberellic Acid-Stimulated) protein. Reporter gene analysis identified consistent expression in anthers and seeds. In anthers expression was developmentally regulated, first appearing at stage 7 of anther development and reaching a maximum at stage 11. Strongest expression was in the tapetum and developing microspores. GASA10 expression also occurred throughout the seed and in root vasculature. GASA10 was shown to be transported to the cell wall. Using GASA1 and GASA6 as positive controls, gibberellic acid was found not to induce GASA10 expression in Arabidopsis suspension cells. Overexpression of GASA10 ( 35S promoter-driven) resulted in a reduction in silique elongation. GASA10 shares structural similarities to the antimicrobial peptide snakin1, however, purified GASA10 failed to influence the growth of a variety of bacterial and fungal species tested. We propose cell wall associated GASA proteins are involved in regulating the hydroxyl radical levels at specific sites in the cell wall to facilitate wall growth (regulating cell wall elongation). [ABSTRACT FROM AUTHOR]

This study describes the development of haploid plantlets through androgenesis in Camellia assamica ssp. assamica (tea). Androgenic haploid embryos were produced through callus formation from microspores during the early-to-late uninucleate stages in anther cultures. A high percentage of callus induction (96%) was obtained on Murashige and Skoog's (MS) medium containing 6% ( w/ v) glucose, supplemented with 5 μM 2,4-dichlorophenoxyacetic acid (2,4-D), 5 μM 6-furfurylaminopurine (kinetin), 800 mg L L-glutamine, and 200 mg L L-serine (callus induction medium). Further proliferation of callus occurred when glucose was replaced with 3% ( w/ v) sucrose in the medium. Embryogenesis was achieved in 85% of the androgenic callus cultures on MS medium containing 10 μM 6-benzylaminopurine (BAP), 3 μM gibberellic acid (GA), 800 mg L L-glutamine, and 200 mg L L-serine (embryo induction medium). Maturation of embryos occurred when the concentration of the growth regulators and adjuvants contained in the embryo induction medium were reduced by tenfold. Embryos germinated into complete plantlets in 65% of the cultures when the MS medium was supplemented with 10 μM BAP, 1 μM indole-3-butyric acid (IBA), 0.5 μM GA, 80 mg L L-glutamine, and 20 mg L L-serine. These plantlets continued to grow when the major salt concentration in the embryo germination medium was reduced by half (1/2 MS). The chromosomal constitution of these in vitro plantlets was confirmed as 2 n = X = 15 by cytological squash preparation of the root tips. Flow cytometric analysis of leaves from these in vitro plantlets confirmed the ploidy status as haploid. This study is an effort to overcome the inherent heterozygosity in tea. [ABSTRACT FROM AUTHOR]

Melon is an important agricultural and economic vegetable crop worldwide. The genetic male sterility mutant (ms-5) has a recessive nuclear gene that controls the male sterility germplasm. Male sterility could reduce the cost of F1 seed production in melon, but heterozygous fertile plants should be removed before pollination. In this study, bulked segregant analysis combined with specific length amplified fragment sequencing was applied to map the single nuclear male sterility recessive gene. A 30-kb candidate region on chromosome 9 located on scaffold 000048 and spanning 2,522,791 to 2,555,104 bp was identified and further confirmed by cleavage amplified polymorphic sequence markers based on parental line resequencing data and classical mapping of 252 F2 individuals. Gene prediction indicated that six annotated genes are present in the 30-kb candidate region. Quantitative RT-PCR revealed significant differences in the expression level of the LOC103498166 ABORTED MICROSPORES (AMS) gene in male-sterile lines (ms-5) and male-fertile (HM1-1) lines during the 2-mm (tetrad) and 5-mm (the first pollen mitosis) periods, and negative regulation of the AMS candidate gene transcription factor was also detected. Sequencing and cluster analysis of the AMS transcription factor revealed five single-nucleotide polymorphisms between the parental lines. The data presented herein suggest that the AMS transcription factor is a possible candidate gene for single nuclear male sterility in melon. The results of this study will help breeders to identify male-sterile and -fertile plants at seeding as marker-assisted selection methods, which would reduce the cost of seed production and improve the use of male-sterile lines in melon. [ABSTRACT FROM AUTHOR]

Ultrastructures of in vitro microspore embryoids and in vivo zygotic embryos of spring wheat have been analyzed and compared. Along with the similarity of ultrastructural characteristics of embryoid and embryo cells at the corresponding developmental stages, some differences have been revealed. Unlike embryos, embryoid cells are characterized by lipid inclusions and numerous mitochondria with well-developed internal membranes. According to our hypothesis, lipids represent an alternative energy source required for active cell divisions in the forming embryoids. Unlike embryos, since the earliest developmental stages, embryoid cells accumulate a significant amount of starch and then utilize it during the organogenesis and germination. A conclusion has been made that embryoid cells create their own reserve of carbohydrates, which is then mobilized during their development. The concept of T.B. Batygina (1987, 1997, 2014) about the universal character of the plant morphogenesis in vivo, in situ, and in vitro has been confirmed. The prospects for the use of microspore embryoidogenesis in vitro as a model to study cytophysiological aspects of zygotic embryogenesis in vivo are discussed. [ABSTRACT FROM AUTHOR]

Resurrection plants of the Selaginellaceae are renowned for their ability to tolerate desiccation as well as the small size of their nuclear genomes. These traits position Selaginella as a promising model system to understand many aspects of plant evolution. However, there is not an established method for the laboratory cultivation of resurrection species of Selaginella. We explored methods of in vitro propagation for resurrection species of Selaginella and identified a set of successful techniques. Our in vitro propagation system included two main steps: surface-sterilized megaspores were cultured alone on C-Fern agar medium for three weeks, followed by the addition of surface-sterilized microspores to the germinated megaspore cultures for co-culture. Sporelings of Selaginella eremophila and S. rupincola were observed after 2-5 weeks of co-culture, and all sporelings survived. Our methods aim to further the interest and use of resurrection species of Selaginella for manipulative studies to better understand the biology of desiccation tolerance and their unique genome architecture. [ABSTRACT FROM AUTHOR]

Fusarium oxysporum species complex (FOSC) is a highly diverse fungus. Recently, F. oxysporum infection was identified from zebrafish ( Danio rerio) culturing system in Korea. Initially, a rapid whitish smudge was appeared in the water with the fungal blooming on walls of fish tanks. Microscopic studies were conducted on fungal hyphae, colony pigmentation and chlamydospore formation and the presence of macro- and microspores confirmed that the isolated fungus as F. oxysporum. Furthermore, isolated F. oxysporum was confirmed by internal transcribed spacer sequencing which matched (100%) to nine F. oxysporum sequences available in GenBank. Experimental hypodermic injection of F. oxysporum into adult zebrafish showed the development of fungal mycelium and pathogenicity similar to signs observed. Histopathologic results revealed a presence of F. oxysporum hyphae in zebrafish muscle. Fusarium oxysporum growth was increased with sea salt in a concentration-dependent manner. Antifungal susceptibility results revealed that F. oxysporum is resistant to copper sulphate (up to 200 μg mL−1) and sensitive to nystatin (up to 40 μg mL−1). This is the first report of FOSC from zebrafish culture system, suggesting it appears as an emerging pathogen, thus posing a significant risk on zebrafish facilities in the world. [ABSTRACT FROM AUTHOR]

Cabbage is an economically important vegetable worldwide. Cabbage Fusarium Wilt (CFW) is a destructive disease that results in considerable yield and quality losses in cole crops. The use of CFW-resistant varieties is the most effective strategy to mitigate the effects of CFW. 01-20 is an elite cabbage line with desirable traits and a high combining ability, but it is highly susceptible to CFW. To rapidly transfer a CFW resistance gene into 01-20 plants, we used microspore cultures to develop 230 doubled haploid (DH) lines from a cross between 01-20 (highly susceptible) and 96-100 (highly resistant). One of the generated DH lines (i.e., D134) was highly resistant to CFW and exhibited a phenotypic performance that was similar to that of line 01-20. Therefore, D134 was applied as the resistance donor parent. We generated 24 insertion-deletion markers using whole genome resequencing data for lines 01-20 and 96-100 to analyze the genomic backgrounds of backcross (BC) progenies. Based on the CFW resistance gene FOC1, a simple sequence repeat (SSR) marker (i.e., Frg13) was developed for foreground selections. We screened 240 BC1 individuals and 280 BC2 individuals with these markers and assessed their phenotypic performance. The proportion of recurrent parent genome (PRPG) of the best individuals in BC1 and BC2 were 95.8 and 99.1%. Finally, a best individual designated as YR01-20 was identified from80 BC2F1 individuals, with homozygous FOC1 allele and genomic background and phenotype almost the same as those of 01-20. Our resultsmay provide a rapid and efficient way of improving elite lines through the combined application of microspore culture, whole-genome background analysis, and disease resistance-specific marker selection. Additionally, the cabbage lines developed in this study represent elite materials useful for the breeding of new CFW-resistant cabbage varieties. [ABSTRACT FROM AUTHOR]

Isolated microspore culture (IMC) is an effective alternative technique for the production of doubled haploid (DH) homozygous lines in plant breeding. However, death of most of the cultured cells during culture is a critical obstacle that affects embryo production in the practical application of IMC technology. In this present paper, we evaluated the effects of two antioxidants of both reduced ascorbate (ASC) and reduced glutathione (GSH) on microspore viability and the induction of embryogenesis in the IMC of broccoli ( Brassica oleracea L. var. italica ). The results showed that cell death occurred soon after stress treatment (at 32.5 °C for 24 h), and the number of dead cells reached about 80% after 2 d. The addition of 10 mg l − 1 ASC and 20 mg l − 1 GSH significantly decreased microspore mortality, and had a strong effect on the number of embryos produced. In the genotype ‘B415’, embryo yields increased approximately 1.2-fold and 2.5-fold after the addition of the 10 mg l − 1 ASC and 20 mg l − 1 GSH, respectively. Moreover, the addition of ASC and GSH also influenced positively the rate of plant regeneration, which respectively increased by 4.2% and 9.7% for ‘B415’. Taken together, our results show that the induction of embryogenesis in broccoli is strongly affected by the use of ASC or GSH. The effects on embryogenesis induction could confirm the importance of the redox environmental regulation in IMC, specifically at the early phase of IMC. The obtained knowledge may accelerate and guide the application of microspore-derived DH plants as a breeding tool in broccoli. [ABSTRACT FROM AUTHOR]

Somatic embryogenesis receptor-like kinases (SERKs), a subfamily of receptor-like kinases, showed important roles in plant response to abiotic and biotic stresses in addition to embryogenesis and organogenesis in numerous plant species. In the present study, three orthologs ofSERKgenes (HvSERK1/2/3) were isolated from barley, and their expression patterns duringin vitroculture of microspores as well as their responses to different stresses including salinity and powdery mildew were characterized. Sequence analysis suggested that threeHvSERKgenes were highly conserved in the grass family. Subcellular localization showed the HvSERK1 protein located on the plasma membrane. TheHvSERK1transcript was up-regulated during the microspore culture period, suggesting its roles in microspore embryogenesis.HvSERK1andHvSERK3showed the highest expression level in the leaves; however no difference was detected forHvSERK2expression in different plants’ tissues. Under salt stress, all threeHvSERKgenes were quickly induced in microspore-derived embryogenic calli, whereas onlyHvSERK1was up-regulated in the roots of barley seedlings. Moreover, onlyHvSERK2was induced in the barley leaves upon powdery mildew inoculation. These results suggest that barleySERKgenes may participate in barley microspores’ development and plant response toward salt and fungal stress, and the function of them has some evolutionary changes. [ABSTRACT FROM PUBLISHER]

Pollen ontogeny in Pancratium maritimum L. was studied from the sporogenous cell to mature pollen grain stages using transmission electron, scanning electron, and light microscopy to determine whether the pollen development in P. maritimum follows the basic scheme in angiosperms or not. In the course of microsporogenesis and microgametogenesis, special attention was given to the considerable ultrastructural changes that are observed in the cytoplasm of microsporocytes, microspores, and mature pollen grains throughout the successive stages of pollen development. Microsporocyte differentiation concerning number and ultrastructure of organelles facilitates the transition of microsporocytes from the sporophytic phase to the gametophytic phase. However, cytoplasmic differentiation of generative and vegetative cells supports their functional distinctness and pollen maturation. Although microsporogenesis and microgametogenesis in P. maritimum generally follow the usual angiosperm pattern, abnormalities such as formation of unreduced gametes were observed. During normal microsporogenesis, meiocytes undergo meiosis and successive cytokinesis, resulting in the formation of isobilateral, decussate, and linear tetrads. Subsequent to the development of free and vacuolated microspores, the first mitotic division occurs and bicellular monosulcate pollen grains are produced. Pollen grains are shed from the anther at binucleate stage. During pollen ontogeny, three periods of vacuolization were observed: in meiocytes, in mononucleate free microspores, and in the generative cell. [ABSTRACT FROM AUTHOR]

In this study, the effects of applications of colchicine on microspore cultures were evaluated in 4 radish (Raphanussativus L.) varieties. For this purpose, 5 different concentrations of colchicine (0, 10, 25, 50, and 75 mg L-1) were applied under dark conditions at 4°C to microspores that had been isolated in Gamborg's medium containing 13% (w/v)sucrose (B5-13). After the application of colchicine the microspores were kept for 1 day at 32.5°C in1/2 x Nitsch and Nitschliquid media supplemented with13% (w/v)sucrose (1/2 NLN-13) at a density of 40.000 microspore mL-1and transferred for culturing under dark conditions at 25°C. Colonies of callus were observed in Petri dishes 4-5 weeks after the microspore isolation. In this study, the 50 mg L-1 dose of colchicine was found to be more effective in terms of callus formation. The highest callus formation was achieved from the large round radish (cv. Burkır) (6.63 calli/Petri dish)and the standard small rooted radish (cv. Cherry Belle)(5.73 calli/Petri dish) varieties. [ABSTRACT FROM AUTHOR]

Viable pollen is essential for plant reproduction and crop yield. Its production requires coordinated expression at specific stages during anther development, involving early meiosis-associated events and late pollen wall formation. The ABORTED MICROSPORES ( AMS) transcription factor is a master regulator of sporopollenin biosynthesis, secretion and pollen wall formation in Arabidopsis. Here we show that it has complex regulation and additional essential roles earlier in pollen formation., An inducible- AMS reporter was created for functional rescue, protein expression pattern analysis, and to distinguish between direct and indirect targets. Mathematical modelling was used to create regulatory networks based on wild-type RNA and protein expression., Dual activity of AMS was defined by biphasic protein expression in anther tapetal cells, with an initial peak around pollen meiosis and then later during pollen wall development. Direct AMS-regulated targets exhibit temporal regulation, indicating that additional factors are associated with their regulation., We demonstrate that AMS biphasic expression is essential for pollen development, and defines distinct functional activities during early and late pollen development. Mathematical modelling suggests that AMS may competitively form a protein complex with other tapetum-expressed transcription factors, and that biphasic regulation is due to repression of upstream regulators and promotion of AMS protein degradation. [ABSTRACT FROM AUTHOR]

Functional pollen is needed to successfully complete fertilization. Pollen is formed inside the anthers following a specific sequence of developmental stages, from microsporocyte meiosis to pollen release, that concerns microsporocytes/microspores and anther wall tissues. The processes involved may not be synchronous within a flower, an anther, and even a microsporangium. Asynchrony has been barely analyzed, and its biological consequences have not been yet assessed. In this review, different processes of pollen development and lifetime, stressing on the possible consequences of their differential timing on pollen performance, are summarized. Development is usually synchronized until microsporocyte meiosis I (occasionally until meiosis II). Afterwards, a period of mostly asynchronous events extends up to anther opening as regards: (1) meiosis II (sometimes); (2) microspore vacuolization and later reduction of vacuoles; (3) amylogenesis, amylolysis, and carbohydrate inter-conversion; (4) the first haploid mitosis; and (5) intine formation. Asynchrony would promote metabolic differences among developing microspores and therefore physiologically heterogeneous pollen grains within a single microsporangium. Asynchrony would increase the effect of competition for resources during development and pollen tube growth and also for water during (re)hydration on the stigma. The differences generated by developmental asynchronies may have an adaptive role since more efficient pollen grains would be selected with regard to homeostasis, desiccation tolerance, resilience, speed of (re)hydration, and germination. The performance of each pollen grain which landed onto the stigma will be the result of a series of selective steps determined by its development, physiological state at maturity, and successive environmental constrains. [ABSTRACT FROM AUTHOR]

A heterosporous lycopsid plant is described from the Upper Devonian (Famennian) Wutong Formation, Changxing County, northern Zhejiang Province, China. The plant is known for its terminal and many detached megasporangiate strobili, most of which do not have sporophylls preserved. Some megasporangiate strobili are closely associated with a vegetative axis bearing leaf cushions and with a mass of microspores. Because of the monosporangiate strobili, the present lycopsid belongs to the Dichostrobiles of the Isoёtales sensu lato. This lycopsid conforms to Changxingia in the vegetative leaves, leaf cushions (including leaf scar and ligule pit), some parts of the megasporophyll (pedicel, heel and lamina), the megasporangium and the megaspores, although the branching pattern of axes, the arrangement and other parts of megasporophyll are still unknown. The fossils are described as Changxingia sp., and this genus is expanded with character of microspore. Hence, the previous and present data indicate that the earliest lycopsids with monosporangiate strobili from the Upper Devonian of China are consistent in Lagenicula megaspores with gula and Lycospora microspores with equatorial cingulum. In contrast, the Carboniferous lycopsids with monosporangiate strobili in Euramerica and Cathaysia show great diversification of both megaspores and microspores. [ABSTRACT FROM AUTHOR]