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Hypocotyl growth during seedling emergence is a crucial developmental transition influenced by light and phytohormones such as ethylene. Ethylene and light antagonistically control hypocotyl growth in either continuous light or darkness. However, how ethylene and light regulate hypocotyl growth, including seedling emergence, during the dark-to-light transition remains elusive. Here, we show that ethylene and light cooperatively stimulate a transient increase in hypocotyl growth during the dark-to-light transition via the light-mediated stabilization of 1-aminocyclopropane-1-carboxylic acid (ACC) synthases (ACSs), the rate-limiting enzymes in ethylene biosynthesis. We found that, in contrast to the known inhibitory role of light in hypocotyl growth, light treatment transiently increases hypocotyl growth in wild-type etiolated seedlings. Moreover, ACC, the direct precursor of ethylene, accentuates the effects of light on hypocotyl elongation during the dark-to-light transition. We determined that light leads to the transient elongation of hypocotyls by stabilizing the ACS5 protein during the dark-to-light transition. Furthermore, biochemical analysis of an ACS5 mutant protein bearing an alteration in the C-terminus indicated that light stabilizes ACS5 by inhibiting the degradation mechanism that acts through the C-terminus of ACS5. Our study reveals that plants regulate hypocotyl elongation during seedling establishment by coordinating light-induced ethylene biosynthesis at the post-translational level. Moreover, the stimulatory role of light on hypocotyl growth during the dark-to-light transition provides additional insights into the known inhibitory role of light in hypocotyl development., (© 2019 The Authors The Plant Journal © 2019 John Wiley & Sons Ltd.)

Anthocyanins contribute to the appearance of fruit by conferring to them a red, blue or purple colour. In a food context, they have also been suggested to promote consumer health. In purple tomato tissues, such as hypocotyls, stems and purple fruits, various anthocyanins accumulate. These molecules have characteristic patterns of modification, including hydroxylations, methylations, glycosylations and acylations. The genetic basis for many of these modifications has not been fully elucidated, and nor has their role in the functioning of anthocyanins. In this paper, AnthOMT, an O-methyltransferase (OMT) mediating the methylation of anthocyanins, has been identified and functionally characterized using a combined metabolomics and transcriptomics approach. Gene candidates were selected from the draft tomato genome, and their expression was subsequently monitored in a tomato seedling system comprising three tissues and involving several time points. In addition, we also followed gene expression in wild-type red and purple transgenic tomato fruits expressing Rosea1 and Delila transcription factors. Of the 57 candidates identified, only a single OMT gene showed patterns strongly correlating with both accumulation of anthocyanins and expression of anthocyanin biosynthesis genes. This candidate (AnthOMT) was compared to a closely related caffeoyl CoA OMT by recombinant expression in Escherichia coli, and then tested for substrate specificity. AnthOMT showed a strong affinity for glycosylated anthocyanins, while other flavonoid glycosides and aglycones were much less preferred. Gene silencing experiments with AnthOMT resulted in reduced levels of the predominant methylated anthocyanins. This confirms the role of this enzyme in the diversification of tomato anthocyanins., (© 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.)

Daily changes in the content of phytohormones accumulating in the hypocotyls of young sunflower seedlings that grow under a 14/10-h light-to-dark (LD) photoperiod were followed using LC–MS. The objective of the work was to investigate whether the presence of light and light transitions lead to visible changes visible in phytohormone levels on the sixth day after the onset of germination. The LC–MS technique used allowed the simultaneous detection of more than one hundred individual phytohormone derivatives, of which the daily accumulation patterns were determined for nearly fifty members. The daily changes in phytohormone levels followed specific patterns for each phytohormone. There were differences between the daytime and nighttime levels, most likely reflecting the effects of light on phytohormone metabolism. A significant difference was found between cytokinins (CKs) and all other phytohormones, so that CK group of phytohormones may be considered to have a separate role in hypocotyl elongation. Prolonged daytime (postponed dusk) resulted in a rapid disruption of rhythmic hypocotyl elongation and it triggered an acute light stress response that was evident in increased levels of a number of important phytohormones from all groups except CKs. However, this light stress, termed ARELD (Acute Response to Extended Light Duration), was not present in control plants grown under continuous light conditions. The data suggest that sunflower has means to adapt to the potentially stressful conditions of continuous light (LL). The qPCR-RT study of the isoforms of circadian clock-associated genes HaLHY, HaTOC1, HaELF3, and HaPIF3 revealed diurnal rhythms under both LD and LL conditions in which the peaks were synchronized and shifted toward the subjective dawn. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Oil Crop Sciences is the property of Oil Crops Research Institute of Chinese Academy of Agricultural Sciences 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.)

Among the most common abiotic stresses that retard the development and growth of plants is salt stress. This study examined the impact of various salt levels (NaCl and Na2SO4) on the germination behaviour of sesame cultivars. Under various simulated salt concentrations (0.05M, 0.01M,0.15M,0.2M,0.25M,0.3M,0.35M,0.4M, and 0.5M), the degree of salinity tolerance of two sesame cultivars, viz., GT-10 and JTS-8 were assessed. The radicle, hypocotyl length, and fresh weight measurements were made separately after 96 and 144 hours. The results revealed that germination and seedling growth drastically decreased as the salt concentration increased. In comparison to GT-10, JTS-8 exhibits greater tolerance to different NaCl concentrations and greater sensitivity to varying Na2SO4 concentrations. [ABSTRACT FROM AUTHOR]

Paubrasilia echinata (brazilwood) is an endangered native tree from the Brazilian Atlantic Forest whose seeds tolerate maturation drying, but, unlike classic orthodox seeds, they quickly lose viability after shedding. This work analyzed the biochemical and ultrastructural changes during the maturation of brazilwood seeds, with particular attention to the cell walls and organization of the cellular components. The physiological seed maturity was accompanied by increased starch content and decreased soluble sugars. Arabinose increased considerably and was the predominant cell-wall sugar during maturation, suggesting a rise in arabinans that contribute to greater cell wall flexibility. This increase was consistent with the cell wall infolding observed in the hypocotyl axis and cotyledons during the maturation of brazilwood seeds. Ultrastructural analyses showed changes in the number and distribution of protein bodies and amyloplasts and the reorganization of lipid droplets into large drops or masses during seed desiccation. Our findings demonstrate that brazilwood seeds behave like other orthodox seeds during maturation, performing the cell wall and metabolic changes before the major decline in the seed water content. However, the high vacuolization and reorganization of lipid bodies observed at 65 DAA suggest that cell deterioration occurs to some extent at the end of the maturation period and could be responsible for reducing the longevity of the brazilwood dried seeds. [ABSTRACT FROM AUTHOR]

The hypocotyls of germinating seedlings elongate in a search for light to enable autotrophic sugar production. Upon exposure to light, photoreceptors that are activated by blue and red light halt elongation by preventing the degradation of the hypocotyl-elongation inhibitor HY5 and by inhibiting the activity of the elongation-promoting transcription factors PIFs. The question of how sugar affects hypocotyl elongation and which cell types stimulate and stop that elongation remains unresolved. We found that overexpression of a sugar sensor, Arabidopsis hexokinase 1 (HXK1), in guard cells promotes hypocotyl elongation under white and blue light through PIF4. Furthermore, expression of PIF4 in guard cells is sufficient to promote hypocotyl elongation in the light, while expression of HY5 in guard cells is sufficient to inhibit the elongation of the hy5 mutant and the elongation stimulated by HXK1. HY5 exits the guard cells and inhibits hypocotyl elongation, but is degraded in the dark. We also show that the inhibition of hypocotyl elongation by guard cells' HY5 involves auto-activation of HY5 expression in other tissues. It appears that guard cells are capable of coordinating hypocotyl elongation and that sugar and HXK1 have the opposite effect of light on hypocotyl elongation, converging at PIF4. Kelly et al. show that Arabidopsis hexokinase1 (HXK1) expressed in guard-cells is sufficient to drive hypocotyl elongation through increasing the activity of PIF4 and auxin level, and competing with the effects of HY5. This study provides insights into how light and sucrose antagonistically coordinate the effort to achieve the height necessary for efficient photosynthetic, autotrophic sugar production. [ABSTRACT FROM AUTHOR]

Vivipary is not a rare finding in papaya fruit. However, this short communication describes the unusual germination of seedling within intra-ovarian ovary. The seedling is attached at two ends of the immature ovary: by radicle at one end, and by elongated tubular structure at the other end. The tubular structure, probably a hypocotyl, mimics an umbilical cord connecting the growing fetus with that of placenta in human embryonic development. [ABSTRACT FROM AUTHOR]

This study was conducted to compare the effects of NaCl, KCl, MgCl2, MgSO4 and CaCl2 on the seed germination and early seedling growth of MTi2. Five types of salts (NaCl, KCl, MgCl2, MgSO4 and CaCl2) at different concentration (50, 100, 150, and 200 mM) and deionized water as control are used. A10 sterilized seeds were placed in petri dishes containing 5ml of deionized water or each salinity solution and kept in the growth chamber at 25 ± 1°C. The experiment is conducted in a completely randomized design with nine replicates. The number of germinated seeds was recorded daily until day 8. The length hypocotyl and radicle length and the biomass of seedlings were measured at day 8. Germination percentage, seed vigor and salt tolerant were calculated. Data were analyzed using SPSS windows version 22. Data are subjected two way ANOVA at p ≤ 0.05 to determine the significant difference between treatment and followed Tukey at p ≤ 0. 05 for means comparison. Results show the response of MTi2 seed on five different salts is significantly different. It indicates that the viability of MTi2 seed to germinate relatively high in KCl followed by NaCl, CaCl2, MgSO4, and MgCl2. [ABSTRACT FROM AUTHOR]

Mung bean [Vigna radiata (L.) Wilczek] is an important grain legume crop. Earlier works on micropropagation protocols for mung bean suffer from genotype dependence, poor reproducibility and insufficient regeneration efficiency. Hence, we made an attempt to develop an efficient protocol for micropropagation of mung bean cv. KM 2 using transverse thin cell layer (tTCL) system. The epicotyl, hypocotyl and nodal tTCL explants were obtained from 5-day-old seedlings and cultured on MS medium with different concentrations of BAP (6-benzylaminopurine), TDZ (Thidiazuron) and kinetin. The maximum frequency (75.25%) of direct shoot initiation and multiplication was achieved from culturing the nodal tTCL explants on MS medium containing 1.0 mg/L BAP. It has been observed that 61.4% of the regenerated shoots successfully elongated and rooted in MS medium containing 1.0 mg/L of IBA (indole-3-butyric acid) after two weeks of culture. The plantlets successfully established under greenhouse conditions with 64% survival rate. The hardened plants exhibited homogeneity and no morphological variations were detected among the regenerants and the mother plants. The identified regeneration system could be efficiently used in various in vitro manipulation studies in mung bean as well. [ABSTRACT FROM AUTHOR]

Somatic embryogenesis from callus induced in epicotyl and hypocotyl segments can be viable native species in order to better -benefit ratio costs, and rates of clonal multiplication. In this sense, two trials were established to induce callus and adventitious buds on hypocotyl and epicotyl segments of cumaru bean seedlings germinated in vitro in different concentrations and combinations of growth regulators. At first, we used the MS medium supplementwith ANA (0.0, 1.5 mg.L-1) and TDZ (0.0, 4.0 and 8.0 mg.L-1) distributed in factorial 2 × 3 × 2 (x auxin cytokinin × explant) with eight replications. In the second, it was used the WPM medium supplemented with BAP (2.0 mg L-1) and plus 2,4-D (2.0 and 4.0 mg L-1) in a factorial 2 × 2 (auxin × explant) with 15 repetitions each. They were evaluating callus formation and the average number of adventitious shoots during the period of 90 days. The results indicated that the highest average for callus formation was observed when the explants were subjected to concentrations of 8.0 mg L-1 TDZ combined with 1.5 mg L-1 ANA in MS medium. For the formation of buds, the WPM medium plus 2.0 mg L-1 2,4-D in the second experiment, induced higher number of shoots, being significant the use of auxin, and its interaction with the type of explant. [ABSTRACT FROM AUTHOR]

A germinating seedling undergoes skotomorphogenesis to emerge from the soil and reach for light. During this phase, the cotyledons are closed, and the hypocotyl elongates. Upon exposure to light, the seedling rapidly switches to photomorphogenesis by opening its cotyledons and suppressing hypocotyl elongation. The E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC 1 ( COP1) is critical for maintaining skotomorphogenesis. Here, we report that jasmonate ( JA) suppresses hypocotyl elongation and stimulates cotyledon opening in etiolated seedlings, partially phenocopying cop1 mutants in the dark. We also find that JA stabilizes several COP1-targeted transcription factors in a COP1-dependent manner. RNA-seq analysis further defines a JA-light co-modulated and cop1-dependent transcriptome, which is enriched for auxin-responsive genes and genes participating in cell wall modification. JA suppresses COP1 activity through at least two distinct mechanisms: decreasing COP1 protein accumulation in the nucleus; and reducing the physical interaction between COP1 and its activator, SUPPRESSOR OF PHYTOCHROME A-105 1 ( SPA1). Our work reveals that JA suppresses COP1 activity to stabilize COP1 targets, thereby inhibiting hypocotyl elongation and stimulating cotyledon unfolding in etiolated Arabidopsis seedlings. [ABSTRACT FROM AUTHOR]

The hypocotyl-derived adventitious root (AR) is an important morphological acclimation to waterlogging stress; however, its genetic basis has not been adequately understood. In the present study, a mixed major gene plus polygene inheritance model was used to analyze AR numbers (ARN) 7 days after waterlogging treatment in six generations (P, P, F, B, B and F), using cucumber waterlogging tolerant line Zaoer-N and sensitive Pepino as parents. The results showed that the genetic model D-4, mixed one negative dominance major gene and additive-dominance polygenes, is the best-fitting genetic model for waterlogging-triggered ARN phenotype. A genetic linkage map spanning 550.8 cM and consisting of 149 simple sequence repeat (SSR) markers segregating into seven linkage groups was constructed. Three QTLs (ARN3.1, ARN5.1, and ARN6.1) distributed on chromosomes 3, 5, and 6 were identified by composite interval mapping. The major-effect QTL, ARN6.1, located between SSR12898 and SSR04751, was the only locus detected in three seasons, with least likelihood (LOD) scores of 8.8, 10.4, and 9.5 and account for 17.6, 24, and 19.8% of the phenotypic variance, respectively. Using five additional single nucleotide polymorphism (SNP) makers, the ARN6.1 was narrowed down to a 0.79 Mb interval franked by SSR12898 and SNP25558853. Illumina RNA-sequencing data generated on hypocotyls of two parents 48 h after waterlogging treatment revealed 15 genes in the 0.79 Mb interval were differentially expressed, including Csa6G503880 encoding a salicylic acid methyl transferase-like protein, Csa6G504590 encoding a cytochrome P450 monooxygenase, and Csa6G505230 encoding a heavy metal-associated protein. Our findings shed light on the genetic architecture underlying adventitious rooting during waterlogging stress in cucumber, and provide a list of potential gene targets for further elucidating waterlogging tolerance in plants. [ABSTRACT FROM AUTHOR]

Background and Aims The underground saxophone stem systems produced by seedlings of certain palm species show peculiar growth patterns and distinctive morphologies, although little information is available concerning their development and function. We studied the ontogenesis of the saxophone stem in Acrocomia aculeata, an important neotropical oleaginous palm, and sought to experimentally define its function. Methods Morpho-anatomical evaluations were performed during 240 d on seedlings using traditional methodologies. The tuberous region of the structure was submitted to histochemical tests and evaluated by transmission electron microscopy. The aerial portions of 130 1- to 3-year-old greenhouse plants were removed and their continuous growth capacity was evaluated after 30 d. Severed saxophone stems were also stored at room temperature (average 25 °C) for up to 90 d and then cultured for 60 d to evaluate root and shoot emission. Key Results The development of the saxophone stem is distinct from other underground systems previously described, and involves three processes: growth and curvature of the cotyledonary petiole, expansion and curvature of the hypocotyl, and expansion of the plumule internodes. The tuberous region stores water and starch, as well as lesser amounts of mucilage and oil. Growth of the aerial portion occurred in 84 % of the separated saxophone stems and in 53 % of the stems held in storage. Conclusions The saxophone stem represents an important adaptation of A. aculeata to anthropogenically impacted and/or dry environments by promoting the burial of both the shoot meristem and storage reserves, which allows the continuous growth of aerial organs. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agrobotanica is the property of Polish Botanical Society / Polskie Towarzystwo Botaniczne 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.)

Physical and morphological characteristics represents quality of raw material, various physical properties of green gram seeds, soaked seeds, sprout and treated (10 and 20 min soaked in essential oil) sprouts were evaluated as a function of moisture content in the range of 10.24 to 89.7% d.b. The average length, width and hundred grain mass of green gram seeds, soaked seeds, sprouts and treated sprouts were 5.85± 0.2, 4.49 ±0.4mm, 6.3±0.1g, 7.01±.01, 5.93± 0.2mm,8.2±0.1g, 9.69±.01, 6.23 ±.01mm, 11.4±0.1g and 9.69±.01, 6.23 ±.01mm, 11.4±0.1g respectively. The geometric mean diameter increased from 5.85mm to 9.69mm, bulk density increased from 0.42 to 0.43 g/ml, tap density increased from 0.48 to 0.49g/ml, car's index increased from 8.16 to 12.2%, angle of repose increased from 30.96° to 33.02° and The static coefficient of friction varied from 0.48 to 0.36 against different six material surfaces and varied from 0.48 to 0.50 in treated samples due to significant effect (p < 0.05) of moisture content within the studied moisture range. Attended studies showed morphological characteriscs of green gram seeds at different seeding densities like 50g, 75g and 100g/500ml water, significant difference (p < 0.05) observed in sprout length, hypocotyl length and hypocotyl weight over different seeding densities. Significant decrease observed in sprout length, hypocotyl length and hypocotyl weight 20.6±0.1,15.3±0.4mm, 5.02±0.01g for 50g/500ml, 15.14±0.08, 9.80±0.5mm, 3.2±0.11g for 75g/500ml, mm,10.34±0.3, 5.01±0.2mm, 1.1±0.05g for 100g/500ml after changing the densities for seeding. [ABSTRACT FROM AUTHOR]

When seedlings grow into young plants their tissue proportions change over time. Viviparous mangrove seedlings of the Rhizophoraceae are different from other young trees. They consist of a thickened cylinder-shaped hypocotyl that allows the seedlings to float and disperse before establishment. Despite the crucial role in the ecological and biogeographical success of mangroves, not much has been published about the internal development of mangrove seedlings in their early life stages. We used X-ray CT-scanning and light microscopy to investigate the internal development (i) over time and (ii) with hypocotyl height in seedlings of the mangrove species Bruguiera gymnorrhiza and Ceriops tagal. While light microscopy offered cell- and tissue identification in destructive transverse sections, X-ray CT-scanning allowed investigating the internal tissue development of living plants over time in a non-destructive way. Our results indicated that the vascular tissue proportionally increased over time and with hypocotyl height in both species in accordance with the growing importance of this tissue in the developing seedlings. As a result, the cortex, composed of an inner and outer zone, proportionally decreased over time and with height in both species. No clear trends over time and with height could be observed regarding the proportion of the pith tissue. A decrease in average density of all tissues together with height was discerned in both species indicating the seedlings were heavier at their base. The latter suggests a supporting role of the seedling base in tidal and wind action. The combination of CT-scanning and light microscopy offered the advantages of both methods in the developmental study of young mangrove plants, and opens perspectives in the study of internal development of young plants in general. [ABSTRACT FROM AUTHOR]

Arabidopsis (Arabidopsis thaliana) Short Hypocotyl in White Light1 (SHW1) encodes a Ser-Arg-Asp-rich protein that acts as a negative regulator of photomorphogenesis. SHW1 and Constitutive Photomorphogenic1 (COP1) genetically interact in an additive manner to suppress photomorphogenesis. Elongated Hypocotyl5 (HY5) is a photomorphogenesis promoting a basic leucine zipper transcription factor that is degraded by COP1 ubiquitin ligase in the darkness. Here, we report the functional interrelation of SHW1 with COP1 and HY5 in Arabidopsis seedling development. The in vitro and in vivo molecular interaction studies show that SHW1 physically interacts with both COP1 and HY5. The genetic studies reveal that SHW1 and HY5 work in an antagonistic manner to regulate photomorphogenic growth. Additional mutation of SHW1 in hy5 mutant background is able to suppress the gravitropic root growth defect of hy5 mutants. This study further reveals that the altered abscisic acid responsiveness of hy5 mutants is modulated by additional loss of SHW1 function. Furthermore, this study shows that SHW1 promotes COP1-mediated degradation of HY5 through enhanced ubiquitylation in the darkness. Collectively, this study highlights a mechanistic view on coordinated regulation of SHW1, COP1, and HY5 in Arabidopsis seedling development. [ABSTRACT FROM AUTHOR]

Plant size is largely determined by the size of individual cells. A number of studies showed a link between ploidy and cell size in land plants, but this link remains controversial. In this study, post-germination growth, which occurs entirely by cell elongation, was examined in diploid and autotetraploid hypocotyls of Arabidopsis thaliana (L.) Heynh. Final hypocotyl length was longer in tetraploid plants than in diploid plants, particularly when seedlings were grown in the dark. The longer hypocotyl in the tetraploid seedlings developed as a result of enhanced cell elongation rather than by an increase in cell number. DNA microarray analysis showed that genes involved in the transport of cuticle precursors were downregulated in a defined region of the tetraploid hypocotyl when compared to the diploid hypocotyl. Cuticle permeability, as assessed by toluidine-blue staining, and cuticular structure, as visualized by electron microscopy, were altered in tetraploid plants. Taken together, these data indicate that promotion of cell elongation is responsible for ploidy-dependent size determination in the Arabidopsis hypocotyl, and that this process is directly or indirectly related to cuticular function. [ABSTRACT FROM AUTHOR]

In nature, root systems of most terrestrial plants are protected from light exposure by growing in a dark soil environment. Hence, in vitro cultivation in transparent Petri dishes leads to physiological perturbations, but the mechanisms underlying root-mediated light perception and responses have not been fully elucidated. Thus, we compared Arabidopsis thaliana seedling development in transparent and darkened Petri dishes at low light intensity (20 μmol m-2 s-1), allowing us to follow (inter alia) hypocotyl elongation, which is an excellent process for studying interactions of signals involved in the regulation of growth and developmental responses. To obtain insights into molecular events underlying differences in seedling growth under these two conditions, we employed liquid chromatography- mass spectrometry (LC-MS) shotgun proteomics (available via the PRIDE deposit PXD001612). In total, we quantified the relative abundances of peptides representing 1,209 proteins detected in all sample replicates of LC-MS analyses. Comparison of MS spectra after manual validation revealed 48 differentially expressed proteins. Functional classification, analysis of available gene expression data and literature searches revealed alterations associated with root illumination (inter alia) in autotrophic CO2 fixation, C compound and carbohydrate metabolism, and nitrogen metabolism. The results also indicate a previously unreported role for cytokinin plant hormones in the escape-tropism response to root illumination. We complemented these results with reverse transcription followed by quantitative PCR (RT-qPCR), chlorophyll fluorescence and detailed cytokinin signaling analyses, detecting in the latter a significant increase in the activity of the cytokinin two-component signaling cascade in roots and implicating the cytokinin receptor AHK3 as the major mediator of root to hypocotyl signaling in responses to root illumination. [ABSTRACT FROM AUTHOR]

BinucleateRhizoctonia(BNR) W7 was evaluated for the efficacy to control damping-off disease in cucumber seedlings. Results revealed that Lobate appresoria and dome-shaped infection cushion were produced by virulentRhizoctonia solaniC9 AG4 on the surface of the cucumber seedling hypocotyls, causing damping-off, 12 h after inoculation. A significant positive correlation was observed between disease severity rating and number of infection cushions (r= 0.94) and appresoria (r= 0.97) on the hypocotyls of seedlings inoculated with virulentR. solaniC9 alone. Inoculation of a nonpathogenic species of BNR prior to virulentR. solanisignificantly reduced the number of appresoria on hypocotyls surface and inhibited the formation of infection cushions that accompanied by highly significant (P≤ 0.01) reduction in disease severity in comparison with seedling inoculated withR. solaniC9 alone. Formation of mucilaginous material upon recognition of the nonpathogenic isolate of BNR followed by hyphal lysis of BNR W7 6 h after inoculation was responsible for reduction in appresorium formation and complete inhibition of infection cushion formation. However, the number of infection structures produced on cucumber was not significantly different for hypocotyls of seedlings inoculated withR. solaniC9 with and without the nonpathogenic BNR W7. [ABSTRACT FROM PUBLISHER]

UV-radiation elicits a suite of developmental (photomorphogenic) and protective responses in plants, but responses early post-germination have received little attention, particularly in intensively bred plants of economic importance. We examined germination, hypocotyl elongation, leaf pubescence and subcellular responses of germinating and/or etiolated soybean (Glycine max (L.) Merr.) seedlings in response to treatment with discrete wavelengths of UV-A or UV-B radiation. We demonstrate differential responses of germinating/young soybean seedlings to a range of UV wavelengths that indicate unique signal transduction mechanisms regulate UV-initiated responses. We have investigated how phenylalanine, a key substrate in the phenylpropanoid pathway, may be involved in these responses. Pubescence may be a key location for phenylalanine-derived protective compounds, as UV-B irradiation increased pubescence and accumulation of UV-absorbing compounds within primary leaf pubescence, visualized by microscopy and absorbance spectra. Mass spectrometry analysis of pubescence indicated that sinapic esters accumulate in the UV-irradiated hairs compared to unirradiated primary leaf tissue. Deleterious effects of some UV-B wavelengths on germination and seedling responses were reduced or entirely prevented by inclusion of phenylalanine in the growth media. Key effects of phenylalanine were not duplicated by tyrosine or tryptophan or sucrose, nor is the specificity of response due to the absorbance of phenylalanine itself. These results suggest that in the seed-to-seedling transition, phenylalanine may be a limiting factor in the development of initial mechanisms of UV protection in the developing leaf. [ABSTRACT FROM AUTHOR]

Key message: This study provides a foundation for further research on root genetic regulation and molecular breeding with emphasis on correlations among root traits to ensure robust root growth and well-developed root systems. Abstract: A set of 447 recombinant inbred lines (RILs) derived from a cross between Jingdou23 (cultivar, female parent) and ZDD2315 (semi-wild, male parent) were used to analyze inheritance and detect QTLs related to root traits at the seedling stage using major gene plus polygene mixed inheritance analysis and composite interval mapping. The results showed that maximum root length (MRL) was controlled by three equivalent major genes, lateral root number (LRN) was controlled by two overlapping major genes, root weight (RW) and volume (RV) were controlled by four equivalent major genes. Hypocotyl length (HL) was controlled by four additive main genes, and hypocotyl weight (HW) was controlled by four additive and additive × additive epistatic, major genes; however, polygene effects were not detected in these traits. Shoot weight (SW) was controlled by multi-gene effects, but major gene effects were not detected. Twenty-four QTLs for MRL, LRN, RW, RV, SW, HL, HW were mapped on LG A1 (chromosome 5), LG A2 (chromosome 8), LG B1 (chromosome 11), LG B2 (chromosome 14), LG C2 (chromosome 6), LG D1b (chromosome 2), LG F_1 (chromosome 13), LG G (chromosome 18), LG H_1 (chromosome 12), LG H_2 (chromosome 12), LG I (chromosome 20), LG K_2 (chromosome 9), LG L (chromosome 19), LG M (chromosome 7), LG N (chromosome 3), LG O (chromosome 10), separately. Root traits were shown to have complex genetic mechanisms at the seedling stage, SW was controlled by multi-gene effects, and the other six traits were controlled by major gene effects. It is concluded that correlations among root traits must be considered to improve the development of beneficial root traits. [ABSTRACT FROM AUTHOR]

The remarkable plasticity of their architecture allows plants to adjust growth to the environment and to overcome adverse conditions. Two examples of environmental stresses that drastically affect shoot development are imminent shade and high temperature. Plants in crowded environments and plants in elevated ambient temperature display very similar phenotypic adaptations of elongated hypocotyls in seedlings and elevated and elongated leaves at later developmental stages. The comparable growth responses to shade and high temperature are partly regulated through shared signaling pathways, of which the phytohormone auxin and the phytochrome interacting factors ( PIFs) are important components. During both shade- and temperature-induced elongation growth auxin biosynthesis and signaling are upregulated in a PIF-dependent manner. In this review we will discuss recent progress in our understanding of how auxin mediates architectural adaptations to shade and high temperature. [ABSTRACT FROM AUTHOR]

The early life of terrestrial seed plants often starts under the soil in subterranean darkness. Over time and through adaptation, plants have evolved an elaborate etiolation process that enables seedlings to emerge from soil and acquire autotrophic ability. This process, however, requires seedlings to be able to sense the soil condition and relay this information accordingly to modulate both the seedlings' growth and the formation of photosynthetic apparatus. The mechanism by which soil overlay drives morphogenetic changes in plants, however, remains poorly understood, particularly with regard to the means by which the cellular processes of different organs are coordinated in response to disparate soil conditions. Here, we illustrate that the soil overlay quantitatively activates seedlings' ethylene production, and an EIN3/EIN3-like 1-dependent ethylene-response cascade is required for seedlings to successfully emerge from the soil. Under soil, an ERF1 pathway is activated in the hypocotyl to slow down cell elongation, whereas a PIF3 pathway is activated in the cotyledon to control the preassembly of photosynthetic machinery. Moreover, this latter PIF3 pathway appears to be coupled to the ERF1-regulated upward-growth rate. The coupling of these two pathways facilitates the synchronized progression of etioplast maturation and hypocotyl growth, which, in turn, ultimately enables seedlings to maintain the amount of protochlorophyllide required for rapid acquisition of photoautotrophic capacity without suffering from photooxidative damage during the dark-to-light transition. Our findings illustrate the existence of a genetic signaling pathway driving soil-induced plant morphogenesis and define the specific role of ethylene in orchestrating organ-specific soil responses in Arabidopsis seedlings. [ABSTRACT FROM AUTHOR]

The strigolactones have been reported in regulating hypocotyl growth in Arabidopsis. This work provides the evidence that strigolactone signaling inhibits hypocotyl elongation dependent on light and the cryptochrome and phytochrome signaling pathway.Seedling development including hypocotyl elongation is a critical phase in the plant life cycle. Light regulation of hypocotyl elongation is primarily mediated through the blue light photoreceptor cryptochrome and red/far-red light photoreceptor phytochrome signaling pathways, comprising regulators including COP1, HY5, and phytochrome-interacting factors (PIFs). The novel phytohormones, strigolactones, also participate in regulating hypocotyl growth. However, how strigolactone coordinates with light and photoreceptors in the regulation of hypocotyl elongation is largely unclear. Here, we demonstrate that strigolactone inhibition of hypocotyl elongation is dependent on cryptochrome and phytochrome signaling pathways. The photoreceptor mutants cry1 cry2, phyA, and phyB are hyposensitive to strigolactone analog GR24 under the respective monochromatic light conditions, while cop1 and pif1 pif3 pif4 pif5 (pifq) quadruple mutants are hypersensitive to GR24 in darkness. Genetic studies indicate that the enhanced responsiveness of cop1 to GR24 is dependent on HY5 and MAX2, while that of pifq is independent of HY5. Further studies demonstrate that GR24 constitutively up-regulates HY5 expression in the dark and light, whereas GR24-promoted HY5 protein accumulation is light- and cryptochrome and phytochrome photoreceptor-dependent. These results suggest that the light dependency of strigolactone regulation of hypocotyl elongation is likely mediated through MAX2-dependent promotion of HY5 expression, light-dependent accumulation of HY5, and PIF-regulated components. [ABSTRACT FROM AUTHOR]

The article discusses the rapid decline in E3 ligase Constitutive Photomorphogenesis1 (COP1) nuclear abundance in response to light and the stabilization of the basic Leu zipper transcription factor Hypocotyl5 (HY5,) one of the targets of COP1. It defines COP1 as a key repressor of photomorphogenesis and explains how light inactivates COP1. It details how COP1 develops nuclear speckles in darkness and investigates the kinetics of HY5 nuclear accumulation.

The present study investigated the effect of ferulic acid (FA; 0-1000 μM) on early growth, and rhizogenesis in mung bean (Vigna radiata) hypocotyls and associated biochemical changes. FA severely affected the radicle elongation and number of secondary roots after 72 h. The root and shoot length, number and length of secondary roots, and seedling dry weight of one-week-old seedlings of mung bean were decreased by 64%. The rooting potential (percent rooting, number and length of adventitious roots) of mung bean hypocotyls under in vitro conditions was significantly inhibited in response to 1-100 μM FA. At 1000 μM there was complete cessation of rooting. FA caused a reduction in the contents of water-soluble proteins and endogenous total phenolics, whereas the activities of proteases, peroxidases, and polyphenol peroxidases increased. The study concludes that FA inhibits root growth and development, and in vitro rooting process in mung bean by interfering with biochemical processes that are crucial for root formation. [ABSTRACT FROM AUTHOR]

Plant peroxisomes play a pivotal role during postgerminative growth by breaking down fatty acids to provide fixed carbons for seedlings before the onset of photosynthesis. The enzyme composition of peroxisomes changes during the transition of the seedling from a heterotrophic to an autotrophic state; however, the mechanisms for the degradation of obsolete peroxisomal proteins remain elusive. One candidate mechanism is autophagy, a bulk degradation pathway targeting cytoplasmic constituents to the lytic vacuole. We present evidence supporting the autophagy of peroxisomes in Arabidopsis thaliana hypocotyls during seedling growth. Mutants defective in autophagy appeared to accumulate excess peroxisomes in hypocotyl cells. When degradation in the vacuole was pharmacologically compromised, both autophagic bodies and peroxisomal markers were detected in the wild-type vacuole but not in that of the autophagy-incompetent mutants. On the basis of the genetic and cell biological data we obtained, we propose that autophagy is important for the maintenance of peroxisome number and cell remodeling in Arabidopsis hypocotyls. [ABSTRACT FROM AUTHOR]

In the dark, etiolated seedlings display a long hypocotyl, the growth of which is rapidly inhibited when the seedlings are exposed to light. In contrast, the phytohormone ethylene prevents hypocotyl elongation in the dark but enhances its growth in the light. However, the mechanism by which light and ethylene signalling oppositely affect this process at the protein level is unclear. Here, we report that ethylene enhances the movement of CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1) to the nucleus where it mediates the degradation of LONG HYPOCOTYL 5 (HY5), contributing to hypocotyl growth in the light. Our results indicate that HY5 is required for ethylene-promoted hypocotyl growth in the light, but not in the dark. Using genetic and biochemical analyses, we found that HY5 functions downstream of ETHYLENE INSENSITIVE 3 (EIN3) for ethylene-promoted hypocotyl growth. Furthermore, the upstream regulation of HY5 stability by ethylene is COP1-dependent, and COP1 is genetically located downstream of EIN3, indicating that the COP1-HY5 complex integrates light and ethylene signalling downstream of EIN3. Importantly, the ethylene precursor 1-aminocyclopropane-1-carboxylate (ACC) enriched the nuclear localisation of COP1; however, this effect was dependent on EIN3 only in the presence of light, strongly suggesting that ethylene promotes the effects of light on the movement of COP1 from the cytoplasm to the nucleus. Thus, our investigation demonstrates that the COP1-HY5 complex is a novel integrator that plays an essential role in ethylene-promoted hypocotyl growth in the light. [ABSTRACT FROM AUTHOR]

During Ca2+ signal transduction, Ca2+-binding proteins known as Ca2+ sensors function to decode stimulus-specific Ca2+ signals into downstream responses. Plants possess extended families of unique Ca2+ sensors termed calmodulin-like proteins ( CMLs) whose cellular roles are not well understood. CML39 encodes a predicted Ca2+ sensor whose expression is strongly increased in response to diverse external stimuli. In the present study, we explored the biochemical properties of recombinant CML39, and used a reverse genetics approach to investigate its physiological role. Our data indicate that Ca2+ binding by CML39 induces a conformational change in the protein that results in an increase in exposed-surface hydrophobicity, a property that is consistent with its predicted function as a Ca2+ sensor. Loss-of-function cml39 mutants resemble wild-type plants under normal growth conditions but exhibit persistent arrest at the seedling stage if grown in the absence of sucrose or other metabolizable carbon sources. Under short-day conditions, cml39 mutants display increased sucrose-induced hypocotyl elongation. When grown in the dark, cml39 mutants show impaired hypocotyl elongation in the absence of sucrose. Promoter-reporter data indicate that CML39 expression is prominent in the apical hook in dark-grown seedlings. Collectively, our data suggest that CML39 functions in Arabidopsis as a Ca2+ sensor that plays an important role in the transduction of light signals that promote seedling establishment. [ABSTRACT FROM AUTHOR]

Although the function of each Z-box binding factor (ZBF) is qualitatively and quantitatively distinct, ZBFs integrate signals from multiple wavelengths of light to coordinate the transcriptional networks for plant growth and development.One set of genes encoding diverse groups of transcription factors that interact with the Z-box (ATACGTGT; a potential Z-DNA forming sequence) is called ZBFs (Z-box Binding Factors). ZBFs include ZBF1, ZBF2, and ZBF3, which encode ZBF1/MYC2 (bHLH), ZBF2/GBF1 (bZIP), and ZBF3/CAM7 (Calmodulin) proteins, respectively. With several recent reports, it is becoming increasingly evident that ZBFs play crucial roles in Arabidopsis seedling photomorphogenesis. ZBFs integrate signals from various wavelengths of light to coordinate the regulation of transcriptional networks that affect multiple facets of plant growth and development. The function of each ZBF is qualitatively and quantitatively distinct. The zbf mutants display pleiotropic effects including altered hypocotyl elongation, cotyledon expansion, lateral root development, and flowering time. In this inaugural review, we discuss the identification, molecular functions, and interacting partners of ZBFs in light-mediated Arabidopsis seedling development. [ABSTRACT FROM AUTHOR]

The present research was carried out to investigate the allelopathic activity ofLitchi chinensisSonn., an important exotic fruit plant of subtropical to tropical areas. The aqueous methanol extract ofL. chinensisleaves at four different concentrations was examined against the germination of lettuce (Lactuca sativaL.) and barnyard grass (Echinochloa crus-galliL. Beauv.), and the seedling growth of cress (Lepidum sativumL.), lettuce, alfalfa (Medicago sativaL.), timothy (Phleum pratenseL.), Italian ryegrass (Lolium multiflorumLam.) and barnyard grass. The hypocotyl/coleoptile and root growth of all test plants were significantly inhibited by the extracts at concentrations ≥0.01 g dry weight equivalent (dry wt. eq.) extract mL−1. The inhibitory activities of the extracts were proportional to the extract concentrations. At concentration 0.1 g dry wt. eq. extract mL−1, the extracts completely inhibited the hypocotyls of cress, lettuce and alfalfa, and the root growth of all test plant species. At the same concentration, a complete inhibition of lettuce seed germination and a significant delay of germination on barnyard grass were also observed. TheI50values for the hypocotyl/coleoptile and root growth of test plants range from 0.002 to 0.079 g dry wt. eq. extract mL−1. These results suggest thatL. chinensisleaf extracts possess allelopathic properties and contain allelopathic substances. Therefore, the plant could be used as a candidate for isolation and identification of those active substances, which may explore the interactions ofL. chinensiswith other neighbouring plants under natural settings. Further, the leaf extracts and/or their residue could be directly used as bioherbicides, or the active substances isolated from this plant may possibly be used as herbicide or templates for new natural, biodegradable herbicide for alternatives of cruel synthetic herbicides in most sustainable manner. To the best of our knowledge this is the first report about the allelopathic activity ofL. chinensis. [ABSTRACT FROM PUBLISHER]

In vitro direct plant regeneration of lucerne was achieved by simultaneous application of thidiazuron ( TDZ) and 6-benzyladenine ( BA) in Murashige and Skoog ( MS) medium. Seedlings were germinated and grown for 6 d on growth regulator-containing MS medium. The shoot tip, consisting of the apical meristem along with parts of the cotyledonary leaves and hypocotyl, was then cultured on a medium containing the growth regulator(s). Adventitious budding of the shoot tip was promoted synergistically by treatment with TDZ and BA, and a maximum of thirty-five shoots per explant was obtained on a medium supplemented with 2 mg L−1 TDZ and 1 mg L−1 BA. Plant regeneration frequency varied from 67 to 93%, and five Indian lucerne cultivars responded well to the regeneration protocol. The Agrobacterium-mediated transformation frequency from co-cultivated explants was 13% following multiple shoot induction. Southern analysis of the T0 plants and T1 progenies confirmed stable inheritance of the hpt marker gene. Agrobacterium infection of the explant caused a significant reduction in the plant regeneration frequency (23%) and the number of shoots induced (11) when compared with uninfected explants. A single shoot tip provided sufficient material to regenerate and establish twenty-seven lucerne plants, whereas only nine plants could be regenerated from an Agrobacterium co-cultivated explant. This transformation protocol could represent a valuable improvement over existing ones for lucerne. [ABSTRACT FROM AUTHOR]

Flavonoids are secondary metabolites present in all terrestrial plants. The flavonoid pathway has been extensively studied, and many of the involved genes and metabolites have been described in the literature. Despite this extensive knowledge, the functioning of the pathway in vivo is still poorly understood. Here, we study the flavonoid pathway using both experiments and mathematical models. We measured flavonoid metabolite dynamics in two tissues, hypocotyls and cotyledons, during tomato seedling development. Interestingly, the same backbone of interactions leads to very different accumulation patterns in the different tissues. Initially, we developed a mathematical model with constant enzyme concentrations that described the metabolic networks separately in both tissues. This model was unable to fit the measured flavonoid dynamics in the hypocotyls, even if we allowed unrealistic parameter values. This suggested us to investigate the effect of transcript abundance on flavonoid accumulation. We found that the expression of candidate flavonoid genes varies considerably with time. Variation in transcript abundance results in enzymatic variation, which could have a large effect on metabolite accumulation. Candidate transcript abundance was included in the mathematical model as representative for enzyme concentration. We fitted the resulting model to the flavonoid dynamics in the cotyledons, and tested it by applying it to the data from hypocotyls. When transcript abundance is included, we are indeed able to explain flavonoid dynamics in both tissues. Importantly, this is possible under the biologically relevant restriction that the enzymatic properties estimated by the model are conserved between the tissues. [ABSTRACT FROM AUTHOR]

During seed maturation, common buckwheat (Fagopyrum esculentum Moench) embryos accumulate sucrose and a-galactosides of d-chiro-inositol (named fagopyritols), which are rare in plant tissues. Although fagopyritols are degraded rapidly during germination, buckwheat seedlings survive desiccation with resumption of growth of hypocotyl tissues but not radicle tissues on rehydration. The objectives were to determine if changes in soluble carbohydrates in hypocotyl and radicle tissues of buckwheat correlated with differential tissue survival after drying seedlings to 0.06 g of water g-1 fresh weight. Buckwheat seeds completed germination between 12 and 24 h after the start of imbibition (HAI) coincident with the loss of survival of radicle tissues after drying. By contrast, hypocotyl tissues of the seedlings at 24, 36, and 48 HAI survived drying and on rehydration formed adventitious roots. During buckwheat seed maturation, embryo axis tissues accumulated sucrose and fagopyritols (64 and 81 mg g-1 dry weight) but little raffinose and stachyose (0.2 and 1.7 mg g-1). During seed hydration, fagopyritols in axis tissues were hydrolyzed before the completion of germination. Sucrose, myo-inositol, and d-chiro-inositol are present in both hypocotyls and radicles before and after drying. During drying of 48-HAI buckwheat seedlings, hypocotyl tissues accumulated much more raffinose (23.2 mg g-1) and stachyose (8.3 mg g-1) than fagopyritols (2.8 mg g-1) whereas none of these compounds accumulated in radicle tissues that were sensitive to drying. An apparent shift in biosynthetic pathways within hypocotyls resulted in raffinose and stachyose accumulation but not fagopyritols during drying of common buckwheat seedlings. The survival of hypocotyl tissues correlated with an increase in concentrations of raffinose, stachyose, and sucrose. [ABSTRACT FROM AUTHOR]

Background and Aims Plants growing at high densities perceive a decrease in the red to far-red (R/FR) ratio of incoming light. These changes in light quality trigger a suite of responses collectively known as the shade-avoidance syndrome (SAS) including hypocotyl and stem elongation, inhibition of branching and acceleration of flowering. Methods Quantitative trait loci (QTLs) were mapped for hypocotyl length to end-of-day far-red (EOD), a simulated shade-avoidance response, in recombinant inbred line (RIL) populations of Arabidopsis thaliana seedlings, derived from Landsberg erecta (Ler) and three accessions (Columbia, Col; Nossen, No-0; and Cape Verde Islands, Cvi-0). Key Results Five loci were identified as being responsible for the EOD response, with a positive contribution of Ler alleles on the phenotype independently of the RIL population. Quantitative complementation analysis and transgenic lines showed that PHYB is the candidate gene for EODRATIO5 in the Ler × Cvi-0 RIL population, but not for two co-localized QTLs, EODRATIO1 and EODRATIO2 mapped in the Ler × No-0 and Ler × Col RIL populations, respectively. The ERECTA gene was also implicated in the SAS in a background-dependent manner. For hypocotyl length EOD response, a positive contribution of erecta alleles was found in Col and Van-0, but not in Ler, Cvi-0, Hir-1 or Ws. Furthermore, pleiotropic effects of ERECTA in the EOD response were also detected for petiole and lamina elongation, hyponastic growth, and flowering time. Conclusions The results show that the analysis of multiple mapping populations leads to a better understanding of the SAS genetic architecture. Moreover, the background- and trait-dependent contribution of ERECTA in the SAS suggest that its function in shaded natural environments may be relevant for some populations in different phases of plant development. It is proposed that ERECTA is involved in canalization processes buffering the genetic variation of the SAS against environmental light fluctuations. [ABSTRACT FROM PUBLISHER]

GLABRA1 ( GL1) belongs to the group of R2R3-MYB transcription factors and is known to be essential for trichome initiation in Arabidopsis. In our previous study, we identified a GL1 ortholog in Brassica rapa as a candidate for the gene controlling leaf hairiness by QTL analysis and suggested that a 5-bp deletion (B-allele) and a 2-bp deletion (D-allele) in the exon 3 of BrGL1 and a non-synonymous SNP (C-allele) in the second nucleotide of exon 3 possibly cause leaf hairlessness. In this study, we transformed a B. rapa line having the B-allele with the A-allele (wild type) or the C-allele of BrGL1 under the control of the CaMV 35S promoter. The transgenic plants with the A-allele showed dense coverage of seedling tissues including stems, young leaves and hypocotyls with trichomes, whereas the phenotypes of those with the C-allele were unchanged. In order to obtain more information about allelic variation of GL1 in different plant lineages and its correlation with leaf hairiness, two GL1 homologs, i.e., RsGL1a and RsGL1b, in Raphanus sativus were analyzed. Allelic variation of RsGL1a between a hairless line and a hairy line was completely associated with hairiness in their BCF population. Comparison of the full-length of RsGL1a in the hairless and hairy lines showed great variation of nucleotides in the 3′ end, which might be essential for its function and expression. [ABSTRACT FROM AUTHOR]

Effects of benzothidiazole (BTH), an inducer of resistance, were examined in a compatible interaction of soybean seedlings and Phytophthora sojae using electron microscopy and quantitative real-time polymerase chain reaction (qRT-PCR) techniques. Seedlings were sprayed with BTH 2 days before inoculation of hypocotyls with zoospore suspension of P. sojae. In hypocotyls treated with BTH, the infection process of P. sojae was significantly delayed, and also the structures of hyphae and haustorium-like bodies were remarkably altered. These changes included increased vacuolation, plasmolysis, degeneration of cytoplasm, and collapse of hyphae and haustorium-like bodies. Large morphological differences were detected in P. sojae-infected hypocotyl tissue treated with BTH compared with infected but non-treated control tissue. Very thick layers of wall appositions were formed in the host cells contacting with hyphae, whereas such structures were never observed in only P. sojae-infected control hypocotyls. In addition, five pathogenesis-related (PR)-genes were selected to detect their transcription changes using qRT-PCR. Expression of PR-1, PR-3a, PR-3b, PR-9, and PR-10 genes were induced in BTH-treated and P. sojae-inoculated tissue at different times and levels. The up-regulated expression of these genes as well as the morphological defense structures may contribute to disease resistance in soybean hypocotyls to P. sojae. [ABSTRACT FROM AUTHOR]

The local environment has a substantial impact on early seedling development. Applying excess carbon in the form of sucrose is known to alter both the timing and duration of seedling growth. Here, we show that sucrose changes growth patterns by increasing auxin levels and rootward auxin transport in Arabidopsis (Arabidopsis thaliana). Sucrose likely interacts with an endogenous carbon-sensing pathway via the PHYTOCHROME-INTERACTING FACTOR (PIF) family of transcription factors, as plants grown in elevated carbon dioxide showed the same PIF-dependent growth promotion. Overexpression of PIF5 was sufficient to suppress photosynthetic rate, enhance response to elevated carbon dioxide, and prolong seedling survival in nitrogen-limiting conditions. Thus, PIF transcription factors integrate growth with metabolic demands and thereby facilitate functional equilibrium during photomorphogenesis. [ABSTRACT FROM AUTHOR]

Plants sense vegetative shade as a reduction in the ratio of red light to far-red light (R:FR). Arabidopsis (Arabidopsis thaliana) responds to a reduced R:FR with increased elongation of the hypocotyl and the leaf petioles as well as with an acceleration of flowering time. The repressor of light signaling, CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), has been shown previously to be essential for the shade-avoidance response in seedlings. Here, we have investigated the roles of COP1 and the COP1-interacting SUPPRESSOR OF PHYA-105 (SPA) proteins in seedling and adult facets of the shade-avoidaalce response. We show that COP1 and the four SPA genes are essential for hypocotyl and leaf petiole elongation in response to low R:FR, in a fashion that involves the COP1/SPA ubiquitination target LONG HYPOCOTYL IN FR LIGHT1 but not ELONGATED HYPOCOTYL5. In contrast, the acceleration of flowering in response to a low R:FR was normal in copl and spa mutants, thus demonstrating that the COP1/SPA complex is only required for elongation responses to vegetative shade and not for shade-induced early flowering. We further show that spa mutant seedlings fail to exhibit an increase in the transcript levels of the auxin biosynthesis genes YUCCA2 (YUC2), YUC8, and YUC9 in response to low R:FR, suggesting that an increase in auxin biosynthesis in vegetative shade requires SPA function. Consistent with this finding, expression of the auxin-response marker gene DR5::GUS did not increase in spa mutant seedlings exposed to low R:FR. We propose that COP1/SPA activity, via LONG HYPOCOTYL IN FR LIGHT1, is required for shade-induced modulation of the auxin biosynthesis pathway and thereby enhances cell elongation in low R:FR. [ABSTRACT FROM AUTHOR]

In order to understand the evolution of the body plan characteristic of the unique aquatic Podostemaceae, seedlings of crustose-rooted species of the Hydrobryum clade, i.e., Hanseniella heterophylla, Hydrobryum loeicum, Hy. tardhuangense, Hy. vientianense and Thawatchaia trilobata, were studied by sectioning and scanning electron microscopy. In all the species the plumule/primary shoot and the radicle/primary root did not form in the seedling. The adventitious root formed exogenously from the lateral side of the hypocotyl and developed initially into a semicircular root, which became crustose during early seedling development. Tufted-leaves arose endogenously from the root. Within the context of the phylogeny of the Hydrobryum clade, we postulate an evolutionary scenario in which the plumule was lost at the divergence of the Hydrobryum clade from the Cladopus clade, much later than the radicle was lost at the divergence of the clade of Podostemoideae and Weddellinoideae from Tristichoideae. The seedling body plan, with the exogenous crustose root playing the role of a leading organ, common in the clade of Hanseniella, Hydrobryum and Thawatchaia, appeared after the divergence of Hydrodiscus with a branched shoot as a leading organ. [ABSTRACT FROM AUTHOR]

The effects of irradiating blue, UV-A, UV-B and a combination of the lights on anthocyanin accumulation at different hypocotyl positions were investigated in seedlings of the purple top turnip ‘Tsuda’. The location of anthocyanin accumulation varied depending on different light spectra. Stronger accumulation of anthocyanin was induced (i) at the upper hypocotyl positions by blue light; (ii) mainly at the upper position, but also at the middle position by UV-B light; and (iii) at the upper to lower position by UV-A light. There were synergistic effects between blue and UV-B, while such effects were not observed for the other light combinations. Among the six chalcone synthase (CHS) genes identified in the ‘Tsuda’ turnip, BrCHS1, 4 and 5 exhibited light-dependent expression patterns, while the other three showed no apparent light responses. The expression of BrCHS1, 4 and 5 was increased particularly by UV-A and blue + UV-B irradiation at the middle to lower hypocotyl positions, in accordance with anthocyanin accumulation patterns. The highest induction of gene expression was observed for BrCHS4 upon blue + UV-B co-irradiation. In contrast, CHS expression was induced only slightly at higher hypocotyl positions by blue light. The R2R3-type MYB transcription factor genes PAP1, MYB4, MYB12 and MYB111 exhibited differential expression patterns at different hypocotyl positions; these patterns were unique for different light spectra. These unique anthocyanin accumulation patterns and gene expression profiles depending on hypocotyl positions and light sources demonstrate that there is a distinct UV-A response, blue + UV-B synergistic response and blue/UV-A light response for anthocyanin biosynthesis in turnip. UV-A light-dependent anthocyanin biosynthesis appeared to be regulated in a manner that is distinct from that mediated by cryptochromes and UV-B photoreceptors. [ABSTRACT FROM AUTHOR]

The sub-cellular events that occur during the ethylene-modulated cell elongation were characterized by examining the ultra-structure of etiolated Arabidopsis seedling hypocotyl cells. Preventing the basal level ethylene response facilitated cell elongation, and the cells exhibited wall loosening and separation phenotype. Nearby the wall separation sites were frequently associated with an increase in the cortical rough endoplasmic reticulum (rER) membranes, the presence of paramural bodies, and the circular Golgi formation. The cortical rER proliferation and circular Golgi phenotype were reverted by the protein biosynthesis inhibitor cycloheximide. The cortical rER membranes were longer when the ethylene response was prevented and shortened with elevated ethylene responses. Proteomic changes between wild type and the ethylene-insensitive mutant ethylene insensitive2 ( ein2) seedling hypocotyls indicated that distinct subsets of proteins involving endomembrane trafficking, remodeling, and wall modifications were differentially expressed. FM4-64 staining supported the proteomic changes, which indicated reduced endocytosis activity with alleviation of the ethylene response. The basal level ethylene response has an important role in endomembrane trafficking, biological materials transport and maintenance of the endomembrane organization. It is possible that endomembrane alterations may partly associate with the wall modifications, though the biological significance of the alterations should be addressed in future studies. [ABSTRACT FROM AUTHOR]

ABSTRACT Plants respond to changes in the environment by altering their growth pattern. Light is one of the most important environmental cues and affects plants throughout the life cycle. It is perceived by photoreceptors such as phytochromes that absorb light of red and far-red wavelengths and control, for example, seedling de-etiolation, chlorophyll biosynthesis and shade avoidance response. We report that the terminal flower2 ( tfl2) mutant, carrying a mutation in the Arabidopsis thaliana HETEROCHROMATIN PROTEIN1 homolog, functions in negative regulation of phytochrome dependent light signalling. tfl2 shows defects in both hypocotyl elongation and shade avoidance response. Double mutant analysis indicates that mutants of the red/far-red light absorbing phytochrome family of plant photoreceptors, phyA and phyB, are epistatic to tfl2 in far-red and red light, respectively. An overlap between genes regulated by light and by auxin has earlier been reported and, in tfl2 plants light-dependent auxin-regulated genes are misexpressed. Further, we show that TFL2 binds to IAA5 and IAA19 suggesting that TFL2 might be involved in regulation of phytochrome-mediated light responses through auxin action. [ABSTRACT FROM AUTHOR]

The effects of different concentrations of copper (Cu) on the growth, Cu accumulation, antioxidant enzyme activity and malondialdehyde (MDA) content of seedlings of the mangrove species Kandelia candel L. were investigated. Seedlings were treated with several concentrations of CuCl2 (0, 1, 5, 10, 20, 30 or 40 mg L−1) for 3 months. The results indicated that a high dose of Cu significantly decreased the growth of K. candel in terms of seedling height, leaf number and total biomass. At the highest Cu concentration (40 mg L−1), there was a 39.53% decrease in final seedling height, a 53.25% decrease in leaf number and a 35.96% decrease in total biomass. Cu ions were accumulated mainly in the roots (96%), and only small amounts were translocated to the hypocotyl, leaves and stem. The MDA content increased with increasing external Cu concentration both in roots and leaves. A significantly higher superoxide dismutase, peroxidase and catalase antioxidative enzyme activity occurred in roots and leaves of plants exposed to 20 mg L−1 CuCl2 compared to other treatments, suggesting that K. candel seedlings can tolerate up to 20 mg L−1 Cu treatment. [ABSTRACT FROM PUBLISHER]

Summary: Stunted, misshapen, necrotic hypocotyls of tomato seedlings (Lycopersicon esculentum L.) germinated on caesium cations in continuous red or white light indicated caesium‐associated hypocotyl photo‐injury. Continuous, far red irradiation inhibited seedling germination in control and caesium treatments but was reversed by continuous white light. Hypocotyl photo‐injury also occurred in far red pretreated seedlings germinated on caesium in continuous white light. Except for suppressed elongation, hypocotyls of caesium‐treated seedlings were normal in appearance. Etiolated caesium‐treated seedlings placed in continuous white light also exhibited hypocotyl photo‐injury. The effects of caesium cations were reversed by potassium cations but not by cations of other alkali metals. [ABSTRACT FROM AUTHOR]

The article discusses a study by F. Lin and colleagues on the role of PINOID (PID)-mediated constitutively photomorphogenic 1 (COP1) phosphorylation in Arabidopsis photomorphogenesis. Topics covered include description of Arabidopsis seedlings, identification of mutation that successfully reverses the short hypocotyl of COP1-6 back to normal, and finding on the PID-mediated COP1 phosphorylation at Ser20.