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Abstract: Key messageMajor A1cytoplasm fertility restoration loci,Rf2andRf5, were found in the West African sorghum. A potential causative mutation forRf2was identified. KASP markers were validated on independent material.Abstract: To accelerate the identification and development of hybrid parental lines in West African (WA) sorghum, this study aimed to understand the genetics underlying the fertility restoration (Rf) in WA A1 cytoplasmic male sterility system and to develop markers for a routine use in WA breeding programs. We genotyped by sequencing three F2 populations to map the Rf quantitative trait loci (QTL), validated the molecular KASP markers developed from those QTL in two F2:3 populations, and assessed the most promising markers on a set of 95 R- and B-lines from WA breeding programs. Seven QTL were found across the three F2 populations. On chromosome SBI-05, we found a major fertility restorer locus (Rf5) for two populations with the same male parent, explaining 19 and 14% of the phenotypic variation in either population. Minor QTL were detected in these two populations on chromosomes SBI-02, SBI-03, SBI-04 and SBI-10. In the third population, we identified one major fertility restorer locus on chromosome SBI-02, Rf2, explaining 31% of the phenotypic variation. Pentatricopeptide repeat genes in the Rf2 QTL region were sequenced, and we detected in Sobic.002G057050 a missense mutation in the first exon, explaining 81% of the phenotypic variation in a F2:3 population and clearly separating B- from R-lines. The KASP marker developed from this mutation stands as a promising tool for routine use in WA breeding programs. [ABSTRACT FROM AUTHOR]

Abstract: Key messageMajor A1cytoplasm fertility restoration loci,Rf2andRf5, were found in the West African sorghum. A potential causative mutation forRf2was identified. KASP markers were validated on independent material.Abstract: To accelerate the identification and development of hybrid parental lines in West African (WA) sorghum, this study aimed to understand the genetics underlying the fertility restoration (Rf) in WA A1 cytoplasmic male sterility system and to develop markers for a routine use in WA breeding programs. We genotyped by sequencing three F2 populations to map the Rf quantitative trait loci (QTL), validated the molecular KASP markers developed from those QTL in two F2:3 populations, and assessed the most promising markers on a set of 95 R- and B-lines from WA breeding programs. Seven QTL were found across the three F2 populations. On chromosome SBI-05, we found a major fertility restorer locus (Rf5) for two populations with the same male parent, explaining 19 and 14% of the phenotypic variation in either population. Minor QTL were detected in these two populations on chromosomes SBI-02, SBI-03, SBI-04 and SBI-10. In the third population, we identified one major fertility restorer locus on chromosome SBI-02, Rf2, explaining 31% of the phenotypic variation. Pentatricopeptide repeat genes in the Rf2 QTL region were sequenced, and we detected in Sobic.002G057050 a missense mutation in the first exon, explaining 81% of the phenotypic variation in a F2:3 population and clearly separating B- from R-lines. The KASP marker developed from this mutation stands as a promising tool for routine use in WA breeding programs. [ABSTRACT FROM AUTHOR]

Key message: Engineered chromosomes 1BS and 1RS offer a new alternative in the development of hybrid systems in bread wheat and triticale. Abstract: In the cytoplasmic male sterility system for hybrid wheat based on the cytoplasm of Triticum timopheevi fertility restoration is difficult, with few good restorer genes available. In the system based on the cytoplasms of Aegilops kotschyi, Ae. uniaristata and Ae. mutica, essentially all chromosomes 1B carry locus Rf that restores male fertility; male sterility manifests itself in wheats with the 1RS.1BL translocation where 1BS chromosome arm is missing. To generate male sterile wheats without the 1RS.1BL translocation, the 1BS arm was cytogenetically engineered to replace the segment with Rf with two short inserts of rye chromatin. Conversely, to enhance fertility restoration by doubling the number of restorers present for eventual use in wheat and triticale, a region of 1BS with Rf was inserted into 1RS. Alloplasmic wheats with Rf removed were completely male sterile; alloplasmic wheats with engineered 1RS carrying Rf and without normal 1B were male fertile. An exception to the ubiquitous presence of Rf is T. spelta var. duhamelianum; four accessions tested in this study gave inconsistent results but some did not restore male fertility. Engineered chromosomes 1BS and 1RS and chromosomes 1B of T. spelta offer a new alternative for practical application of a cytoplasmic male sterility system in the development of hybrid wheat and hexaploid triticale. [ABSTRACT FROM AUTHOR]

Key message: Using DArT analysis, we demonstrated that all Solanum × michoacanum (+) S. tuberosum somatic hybrids contained all parental chromosomes. However, from 13.9 to 29.6 % of the markers from both parents were lost in the hybrids. Abstract: Somatic hybrids are an interesting material for research of nucleus-cytoplasm interaction and sources of new nuclear and cytoplasmic combinations. Analyses of genomes of somatic hybrids are essential for studies on genome compatibility between species, its evolution and are important for their efficient exploitation. Diversity array technology (DArT) permits analysis of the composition of nuclear DNA of somatic hybrids. The nuclear genome compositions of 97 Solanum × michoacanum (+) S. tuberosum [ mch (+) tbr] somatic hybrids from five fusion combinations and 11 autofused 4 x mch were analyzed for the first time based on DArT markers. Out of 5358 DArT markers generated in a single assay, greater than 2000 markers were polymorphic between parents, of which more than 1500 have a known chromosomal location on potato genetic or physical map. DArT markers were distributed along the entire length of 12 chromosomes. We noticed elimination of markers of wild and tbr fusion components. The nuclear genome of individual somatic hybrids was diversified. Mch is a source of resistance to Phytophthora infestans. From 97 mch (+) tbr somatic hybrids, two hybrids and all 11 autofused 4 x mch were resistant to P. infestans. The analysis of the structure of particular hybrids' chromosomes indicated the presence of markers from both parental genomes as well as missing markers spread along the full length of the chromosome. Markers specific to chloroplast DNA and mitochondrial DNA were used for analysis of changes within the organellar genomes of somatic hybrids. Random and non-random segregations of organellar DNA were noted. [ABSTRACT FROM AUTHOR]

Interspecific hybridization can be considered an accelerator of evolution, otherwise a slow process, solely dependent on mutation and recombination. Upon interspecific hybridization, several novel interactions between nuclear and cytoplasmic genomes emerge which provide additional sources of diversity. The magnitude and essence of intergenomic interactions between nuclear and cytoplasmic genomes remain unknown due to the direction of many crosses. This study was conducted to address the role of nuclear-cytoplasmic interactions as a source of variation upon hybridization. Wheat ( Triticum aestivum) alloplasmic lines carrying the cytoplasm of Aegilops mutica along with an integrated approach utilizing comparative quantitative trait locus (QTL) and epigenome analysis were used to dissect this interaction. The results indicate that cytoplasmic genomes can modify the magnitude of QTL controlling certain physiological traits such as dry matter weight. Furthermore, methylation profiling analysis detected eight polymorphic regions affected by the cytoplasm type. In general, these results indicate that novel nuclear-cytoplasmic interactions can potentially trigger an epigenetic modification cascade in nuclear genes which eventually change the genetic network controlling physiological traits. These modified genetic networks can serve as new sources of variation to accelerate the evolutionary process. Furthermore, this variation can synthetically be produced by breeders in their programs to develop epigenomic-segregating lines. [ABSTRACT FROM AUTHOR]

In this study, the atp8 gene was cloned from the cytoplasmic male sterile (CMS) line UG93A and its maintainer line UG93B in kenaf. Its DNA sequence analysis showed that atp8 containing 480-bp, encoding 159 amino acid residues, and a 9-bp insertion was found at the 3′flanking sequence in UG93A compared with UG93B. The cDNA sequence of atp8 analyzed by RT-PCR indicated that there were five loci edited, but six loci edited in UG93B. The editing frequencies were higher in sterile cytoplasm than in fertile cytoplasm. The relative expression of atp8 analyzed by real-time PCR showed that the expressed level of atp8 in UG93A was lower than that of its maitainer UG93B and its F hybrid UG93A/992 (a restore line). Furthermore, based on the difference of the 9-bp differences at the 3′flanking sequence of atp8 between UG93A and UG93B, a molecular marker specific to male sterile cytoplasm was developed, which can be used for indentifying whether any germplasm of kenaf is male sterile cytoplasm or male fertile cytoplasm. [ABSTRACT FROM AUTHOR]

A study of latex harvesting technologies, appropriate to the opening of tapping of Hevea brasiliensis clone GT 1 having moderate metabolism, was undertaken in south eastern Côte d'Ivoire. Rubber trees were planted in 1989 at a density of 510 trees/ha and harvesting was started in 1995. Ten different latex harvesting systems were tested and monitored for seven years. The parameters measured were rubber yield, isodiametric growth of the trunk, physiological profile and sensitivity to tapping panel dryness. The results showed that tapping with hormonal stimulation highly activated the metabolism of latex vessels. They also indicated that the tapping opening at the height of 1.20m from the ground level of downward tapping showed high yield than the opening at 0.70m in upward tapping and not followed by downward tapping for a minimum period equivalent to four years. Half-spiral upward tapping from the fifth year certainly induces very high yield. However, a high rate of tapping panel dryness and signs of early physiological fatigue were observed, probably due to over-exploitation. The different hormonal stimulation strategies caused little damage on the growth of the trunk and the physiological parameters of the latex. The latex harvesting system which is most suitable for clone GT 1, at opening is S/2 d4 6d/7 12 m/12.ET2.5% Pa1 (1) 4/y at 1.20m above ground. Furthermore, it was indicated that upward tapping could be introduced at least after the fifth year. [ABSTRACT FROM AUTHOR]

Lippia alba (Verbenaceae) is an aromatic shrub recently described as a new tropical polyploid species with five distinct chromosome numbers (2 n = 30, 38, 45, 60, and 90) with 2 n = 30, 45, and 60 being the most frequent ones. Cytomixis is a cellular process known as the migration of genetic material mainly between meiocytes through cytoplasmic connections or cytomictic channels. This phenomenon has been reported in various plant families such as Leguminosae, Brassicaceae, Poaceae, Apocynaceae, Liliaceae, Rutaceae, and others. The transference of genetic material between pollen mother cells (PMCs), by cytomictic channels, induces the formation of unbalanced and unreduced (2 n) gametes, and is considered a possible source of aneuploid and polyploid plants. Here, we describe for the first time, the occurrence of cytomixis in meiotic cells of L. alba (tetraploid cytotype) analyzing data obtained from meiotic behavior assays. In addition, the pollen size and viability were also evaluated. A high index of irregularities during meiosis was observed as well as unviable pollen with heterogeneous size. Approximately 80 % of zygotene cells showed genetic material exchange. Considering that L. alba shows different chromosome numbers, the contribution of cytomixis to cytotypes formation is also discussed. [ABSTRACT FROM AUTHOR]

Male sterile (MS) plants fail to produce functional anthers, pollen, or male gametes. This condition is useful in sunflower hybrid seed production. A MS form identified in an invasive population of H. annuus located in Las Malvinas was characterized by 37 morphological variables, six mitochondrial genes ( atpA, atp6, coxIII, orfb, orfB and orfC) associated with cytoplasmic male sterility (CMS), five SSR loci associated with ms9, ms10, and ms11 nuclear male sterility genes, and the HRGO2 marker associated with the Rf1 fertility restoration gene for CMS-PET1. Restoration of MS condition was evaluated through crosses with 13 sunflower inbred lines. Las Malvinas site was described regarding its population size, spatial distribution, and male sterility occurrence. Ten years after the first observation, population size was over 250,000 individuals. The adoption of this species as ornamental plant in home gardens has contributed its expansion. The low frequency of MS plants found in natural conditions (0.4 %) is concordant with a CMS form in combination with restoration genes. Wild individuals harboring the CMS-PET1 cytoplasm and individuals carrying a different mitochondrial genome were found. The Rf1 restorer gene for CMS-PET1 was not detected. The new type of male sterility was different than CMS-PET1 in pollen morphology; absence of orfC; and different response to crosses with inbred lines. Molecular differences were found with CMS-RES1 and CMS-MAX1. The male sterility could not be explained by differences in the cytoplasmic or nuclear regions studied. The new MS form will expand the genetic diversity available for commercial hybrid sunflower production. [ABSTRACT FROM AUTHOR]

In this study, the morphology, cytology and crossability of amphidiploid hybrids (2n = 8x = 80; WWW′W′TTT′T′) between Nicotiana wuttkei × Nicotiana tabacum were studied. An R progeny of the hybrids were produced through in vitro chromosome doubling of the N. wuttkei × N. tabacum cv. Wiślica amphihaploids. The resulting amphidiploids showed enough self-fertility to be perpetuated by self-pollination. The plants preserved their phenotypes and the number of chromosomes over subsequent R-R selfed generations. During metaphase I the bivalent number increased progressively over the generations R to R and averaged 36.9, 37.4, 38.6 and 38.7, respectively. In addition, a progressive increase in pollen viability was observed: 50.8, 55.5, 62.3 and 65.7 % in generations from R to R, respectively. Genomic in situ hybridization of R plants revealed recombination between the parental species on two chromosomes. Reciprocal crosses of R generation amphidiploids to N. tabacum cv. Wiślica yielded sesquidiploid hybrids (2n = 6x = 64; WW′TTT′T′). When N. tabacum cv. Wiślica is the pollinator, the amphidiploid gave rise to a total of 25 sesquidiploid plants with the cytoplasmic genome of N. wuttkei, while the reverse mating resulted in a mixed population consisting of a single sesquidiploid plant with the cytoplasm of N. tabacum and 203 plants of supposedly maternal origin. Our amphidiploid N. wuttkei × N. tabacum cv. Wiślica can be concluded as sufficiently stable and is regarded as a new artificial hybrid species. [ABSTRACT FROM AUTHOR]

Main conclusion: The role of mannitol differs from that of glucose, fructose and sucrose in sepal cell expansion associated with flower opening in Delphinium × belladonna. Sepals of Delphinium × belladonna are colored and much larger than the petals. To determine whether the role of mannitol in sepal growth associated with flower opening differs from those of ubiquitous metabolic sugars including glucose, fructose and sucrose, we investigated changes in cell number, subcellular concentrations of soluble carbohydrates, and osmotic potential in sepals during flower opening in Delphinium × belladonna cv. Bellamosum. The number of epidermal cells in the sepals did not increase from the stage when sepal pigmentation started, whereas the cell area increased during flower opening, indicating that petal growth during flower opening depends on cell expansion. Mannitol concentrations in the vacuole at three different stages were approximately 100 mM, which were much higher than the other carbohydrate concentrations, but they decreased slightly at open stage. In contrast, mannitol concentration in the cytoplasm was 56 mM at bud stage, but it increased to 104 mM at open stage. Glucose and fructose concentrations in the vacuole at open stage increased to 45 and 56 mM, respectively. Total osmotic potential in apoplast and symplast, which was partially due to soluble carbohydrates, was almost constant during flower opening. Therefore, mannitol may be acting constitutively as the main osmoticum in the vacuole where it may contribute to the maintenance of the osmotic balance between the cytoplasm and vacuole in open flowers. The role of mannitol differs from those of glucose, fructose, and sucrose in sepal cell expansion in Delphinium × belladonna. [ABSTRACT FROM AUTHOR]

Main conclusion: Discrete categories of seed physiology can be explained through a unified concept of the structural and molecular mobility responses within cells to drying. Tolerance of desiccation is typically described by a threshold or low water content limit to survival. This convention provides fairly good distinction between orthodox and recalcitrant seeds, which show thresholds of less than about 0.07 and greater than about 0.2 g HO g DW, respectively. Threshold water contents, however, are not direct measures of the intensity of water stress tolerated by seeds, nor are they measures of cell response to water stress. More direct criteria, that accommodate both spatial and temporal effects of water loss, are required to explain variation of desiccation tolerance and longevity in seeds from diverse genetic backgrounds and growth conditions. This essay presents the argument that changes in cellular volume directly quantify primary responses to desiccating stress in a context that also links damage, as cellular constituents compress, and protection, as compressed molecules form stabilizing structure. During desiccation, fluid cytoplasm solidifies, and the newly formed spatial relationships among molecules determine whether and how long viability is maintained. The diversity of seed behaviors suggests complexity and opportunity to discover molecules and mechanisms that regulate survival and perception of time in cells that lack metabolic function. [ABSTRACT FROM AUTHOR]

For the first time, the developmental events in the course of exine structure establishment have been traced in detail with TEM in Eupomatia, with the addition of cytochemical tests. A new look at unfolding events is suggested using our recent hypothesis on self-assembling micellar mesophases. The process proved to be unusual and includes 'ghost' stages. The first units observed in the periplasmic space are spherical ones (= normal spherical micelles). These accumulate, resulting in a granular layer up to middle tetrad stage. Sporopollenin precursor accumulation on these units makes the ectexine layer looking as homogenous at late tetrad stage. Simultaneously, the columns of globules are added in the periplasmic space, which reminds an attempt to form columellae; but, the process failed. Instead, a fimbrillate endexine layer of compressed globules appears. The latter augments via additional globules, appearing in the periplasmic space in the free microspore period. The endexine formation is double-stepped spatially and temporally. The second, lamellate endexine layer (laminate micelles) appears late in development, when the channeled intine-I is already established-a very unusual feature. Moreover, a 'fenestrated' stage comes unexpectedly at vacuolate stage, when hitherto amorphous ectexine appears pierced by cavernae-the results of reversal of normal spherical micelles (constituents of ectexine) to reverse the ones that open their cores for the entrance of hydrophilic nutrients from tapetum and give them over to the microspore cytoplasm by exchanging their solubilizates. [ABSTRACT FROM AUTHOR]

To reveal the linkage relationship between the Ms locus, a restorer-of-fertility gene for cytoplasmic male-sterility (CMS) caused by CMS-S cytoplasm in onion ( Allium cepa L.) and previously reported molecular markers linked to the Ms locus, 11 recombinants selected from 4,273 segregating plants originating from the cross between male-sterile maternal and male-fertile paternal lines were analyzed. Results showed that genotypes of a codominant marker, jnurf12, were perfectly matched with the male-fertility phenotypes in all recombinants, but that this marker was not applicable in diverse breeding lines due to multiple band patterns. For the development of more reliable markers, a 12-bp indel was identified from the sequences which were obtained by genome walking, and was used to develop a simple PCR marker which was designated jnurf13. When 104 diverse breeding lines containing CMS-S cytoplasm were analyzed with the jnurf13 marker, male-fertility phenotypes of all breeding lines were perfectly matched with marker genotypes. To our surprise, phenotypes of 153 breeding lines containing CMS-T-like cytoplasm were also matched with genotypes of the jnurf13 marker which was linked to the Ms locus for the CMS-S system. Furthermore, phenotypes of four F populations containing CMS-T-like cytoplasm co-segregated perfectly with jnurf13 genotypes. Allelic segregation distortion was detected in two F populations using the jnurf13 maker. The results of this study were in conflict with a previous model for inheritance of fertility restoration in the CMS-T system. Therefore, we proposed a new model based on the data analyzed with the jnurf13 marker, which was in linkage disequilibrium with restorer-of-fertility genes for both CMS systems. [ABSTRACT FROM AUTHOR]

Cytoplasmic male sterility (CMS) is an important factor to observe heterosis in Brassica rapa. Although several studies have documented the rearrangements of mitochondrial DNA and dysfunction in the mitochondria have been observed in most types of CMS, the basis of the molecular mechanisms involved in these processes and other effects on CMS remain unclear. In this study, suppression subtractive hybridization was performed in the flowers of an alloplasmic Polima CMS system from B. rapa ssp. chinensis to identify genes that are differentially expressed between fertile and sterile plants. A total of 443 clones were isolated (156 were upregulated in fertile buds, and 287 were upregulated in sterile ones). Real-time RT-PCR further demonstrated the credibility of SSH. Among these genes, many membrane protein genes ( LTP12, PIP2A, and GRP14) were inhibited in the sterile male line. Mitochondrial membrane potential (MMP) assay was then performed. Results showed that the sterile MMP was unstable and failed to create a potential difference; thus, mitochondrial dysfunction occurred. Moreover, abnormal microtubules and photosynthetic pathways were found in sterile male cells. Unstable MMP, nutritional deficiency, and abnormal microtubules were the causes of Polima CMS in Brassica campestris. HO, MDA, and O, accumulated as byproducts of energy metabolism disorder in sterile male cells. [ABSTRACT FROM AUTHOR]

Key message: Divergent wild and endemic peas differ in hybrid sterility in reciprocal crosses with cultivated pea depending on alleles of a nuclear 'speciation gene' involved in nuclear-cytoplasmic compatibility. Background: In hybrids between cultivated and wild peas, nuclear-cytoplasmic conflict frequently occurs. One of the nuclear genes involved, Scs1, was earlier mapped on Linkage Group III. Results: In reciprocal crosses of seven divergent pea accessions with cultivated P. sativum, some alleles of Scs1 manifested incompatibility with an alien cytoplasm as a decrease in pollen fertility to about 50 % in the heterozygotes and lack of some genotypic classes among F2 segregants. Earlier, we defined monophyletic evolutionary lineages A, B, C and D of pea according to allelic state of three markers, from nuclear, plastid and mitochondrial genomes. All tested representatives of wild peas from the lineages A and C exhibited incompatibility due to Scs1 deleterious effects in crosses with testerlines of P. sativum subsp. sativum (the common cultivated pea) at least in one direction. A wild pea from the lineage B and a cultivated pea from the lineage D were compatible with the testerline in both directions. The tested accession of cultivated P. abyssinicum (lineage A) was partially compatible in both directions. The Scs1 alleles of some pea accessions even originating from the same geographic area were remarkably different in their compatibility with cultivated Pisum sativum cytoplasm. Conclusion: Variability of a gene involved in reproductive isolation is of important evolutionary role and nominate Scs1 as a speciation gene. [ABSTRACT FROM AUTHOR]

Pollen grains of three Brazilian species of Passiflora ( P. elegans, P. suberosa and P. haematostigma) belonging to different subgenera were studied with respect to the wall and cytoplasm. New data were obtained on pollen wall histochemistry, cytoplasm contents and organelle inheritance. The structure of the pollen wall layers differed in all the species; P. elegans shares characters with those found in other species from the same subgenus. The exine foot layer is structured and evident only in P. haematostigma and is not structured in P. elegans. The pollen grains have pollenkitt with lipid components. The cytoplasm of the vegetative cell contains dissolved and non-dissolved polysaccharides. The generative cell contains plastids and mitochondria in all the species analyzed, and consequently has the potential for paternal or biparental extranuclear inheritance. Aspects of the evolution of the characters of the species are discussed in the light of a recent phylogeny of the group, with a focus on the three subgenera. [ABSTRACT FROM AUTHOR]

Our previous studies have described the purification and characterization of a novel plant NAD(P)-reductase like protein (RL) from the thermogenic appendix of the Sauromatum guttatum inflorescence. RL is mainly located in cytoplasm of thermogenic plants and it can act like a bistable switch. It adopts a compact conformation during heat-production and a more expanded conformation when heat is not generated. Addition of salicylic acid, a natural thermogenic inducer, at picomolar concentration to a solution of purified RL induced a discontinuous volume phase transition in which the volume of RL in the oligomeric form expanded and shrunk repeatedly every 4–5 min. In the present study using ESI–MS analysis we have demonstrated the existence of RL in the human SK-N-SH cell line and in mouse brain tissue. The molecular mass of human RL is in the same range as of its plant counterpart, 34,140 ± 34 Da. The charge state distribution of the human RL is identical to its plant counterpart from the Sauromatum appendix during heat-production. Human RL was present in the compact state when it was purified from the SK-N-SH cell line When these cells were treated with salicylic acid (10 μM) a shift to a much more compact conformation was observed. It seems that the potential of RL to respond to salicylic acid was conserved. These results may reveal the existence of a thermoregulation system that is evolutionarily conserved and is operating by conformational changes. This discovery may also represent an opportunity for a better understanding of some of the diverse functions of salicylic acid and aspirin in plants and humans. [ABSTRACT FROM AUTHOR]

In 1994, Oku reported that plant pathogens, mainly fungal pathogens, require three essential abilities to infect plants: to enter plants, to overcome host resistance, and to evoke disease. Because the infectious process of phytopathogenic bacteria differs from that of fungal pathogens, we have attempted to characterize pathogenicity, the ability of a pathogen to cause disease, using the phytopathogenic bacterium Pseudomonas syringae as a representative pathogen. To establish infection and incite disease development, bacteria first have to enter a plant. This process requires flagella- and type IV pili-mediated motility, and active taxis is probably necessary for effective infection. After bacteria enter a plant's apoplastic spaces, they need to overcome host plant resistance. To do this, they secrete a wide variety of hypersensitive response and pathogenicity (Hrp) effector proteins into the plant cytoplasm to interfere with pathogen/microbe-associated molecular pattern- and effector-triggered immunity, produce phytohormones and/or phytotoxins to suppress plant defense responses and extracellular polysaccharides to prevent access by antibiotics and to chelate Ca, and activate the multidrug resistance efflux pump to extrude antimicrobial compounds for successful colonization. Furthermore, to evoke disease, bacteria produce toxins and Hrp effectors that compromise a plant's homeostasis and injure plant cells. The expression of these virulence factors depends on the infection processes and environmental conditions. Thus, the expression and function of virulence factors interact with each other, creating complex networks in the regulation of bacterial virulence-related genes. [ABSTRACT FROM AUTHOR]

The genus Taraxacum Wigg. (Asteraceae) forms a polyploid complex within which there are strong links between the ploidy level and the mode of reproduction. Diploids are obligate sexual, whereas polyploids are usually apomictic. The paper reports on a comparative study of the ovary and especially the ovule anatomy in the diploid dandelion T. linearisquameum and the triploid T. gentile. Observations with light and electron microscopy revealed no essential differences in the anatomy of both the ovary and ovule in the examined species. Dandelion ovules are anatropous, unitegmic and tenuinucellate. In both sexual and apomictic species, a zonal differentiation of the integument is characteristic of the ovule. In the integumentary layers situated next to the endothelium, the cell walls are extremely thick and PAS positive. Data obtained from TEM indicate that these special walls have an open spongy structure and their cytoplasm shows evidence of gradual degeneration. Increased deposition of wall material in the integumentary cells surrounding the endothelium takes place especially around the chalazal pole of the embryo sac as well as around the central cell. In contrast, the integumentary cells surrounding the micropylar region have thin walls and exhibit a high metabolic activity. The role of the thick-walled integumentary layers in the dandelion ovule is discussed. We also consider whether this may be a feature of taxonomic importance. [ABSTRACT FROM AUTHOR]

Key message: Pollen mRNAs were different in reciprocal F hybrids, which were probably caused by a cytoplasm-nuclear chromosomal genes interaction. Abstract: We have found reciprocal differences in crossability between F hybrids of Solanum tuberosum (T) and a Mexican wild potato species S. demissum (D). When the reciprocal hybrids were crossed as pollen parents with S. demissum, a significantly higher berry-setting rate was obtained in TD compared with DT. In this study, we performed a whole-genome transcript analysis of the pollen mRNA using a high-throughput sequencer. We obtained 12.6 billion bases that were aligned into 13,020 transcripts with 9,366 loci. All possible genetic modes were observed between the parents and their progeny, where over-dominance and under-recessive types were relatively frequent (15.7 and 15.3 %, respectively). We found that 59.1 % of transcripts were more abundant in TD and over fourfold higher transcription levels were found in 66 TD transcripts and three DT transcripts. A higher proportion of over-dominance and a lower proportion of under-recessive transcription types were also observed in TD. The percentage contributions of multiple transcripts at the same locus varied greatly and were transcribed differently between species. In the new allelic combinations created by hybridization, approximately three-fourth of the transcripts had intermediate percentage contributions between the parents but no differential transcription patterns were apparent between the reciprocal hybrids. A broad spectrum of functionally different nuclear genes was over-represented in TD pollen, some of which were directly related to pollen behavior. Since TD and DT pollen had the same composition of nuclear genes, a cytoplasm-nuclear chromosomal genes interaction is suggested for the cause of transcriptional and phenotypic differences between reciprocal hybrids. [ABSTRACT FROM AUTHOR]

Plant cytoplasmic male sterility (CMS) results from incompatibilities between the organellar and nuclear genomes and prevents self pollination, enabling hybrid crop breeding to increase yields. The Wild Abortive CMS (CMS-WA) has been exploited in the majority of 'three-line' hybrid rice production since the 1970s, but the molecular basis of this trait remains unknown. Here we report that a new mitochondrial gene, WA352, which originated recently in wild rice, confers CMS-WA because the protein it encodes interacts with the nuclear-encoded mitochondrial protein COX11. In CMS-WA lines, WA352 accumulates preferentially in the anther tapetum, thereby inhibiting COX11 function in peroxide metabolism and triggering premature tapetal programmed cell death and consequent pollen abortion. WA352-induced sterility can be suppressed by two restorer-of-fertility (Rf) genes, suggesting the existence of different mechanisms to counteract deleterious cytoplasmic factors. Thus, CMS-related cytoplasmic-nuclear incompatibility is driven by a detrimental interaction between a newly evolved mitochondrial gene and a conserved, essential nuclear gene. [ABSTRACT FROM AUTHOR]