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Summary: The homology of the single cotyledon of grasses and the ontogeny of the scutellum and coleoptile as the initial, highly modified structures of the grass embryo are investigated using leaf developmental genetics and targeted transcript analyses in the model grass Zea mays subsp. mays.Transcripts of leaf developmental genes are identified in both the initiating scutellum and the coleoptile, while mutations disrupting mediolateral leaf development also disrupt scutellum and coleoptile morphology, suggesting that these grass‐specific organs are modified leaves.Higher‐order mutations in WUSCHEL‐LIKE HOMEOBOX3 (WOX3) genes, involved in mediolateral patterning of plant lateral organs, inform a model for the fusion of coleoptilar margins during maize embryo development.Genetic, RNA‐targeting, and morphological evidence supports models for cotyledon evolution where the scutellum and coleoptile, respectively, comprise the distal and proximal domains of the highly modified, single grass cotyledon. [ABSTRACT FROM AUTHOR]

Since the acid growth theory was introduced in plant physiology and mainframe computers became more widely available in the mid-20th century, there has been a growing need to accurately predict plant cell morphological parameters during growth. This article presents a computer program that uses an original numerical method to solve a highly nonlinear growth equation. The program is written in Python, a popular open-source scientific software environment called CoCalc or SAGE. This program can be used to determine the growth of an individual plant cell or multicellular organ, such as a coleoptile or hypocotyl segment, at the non-meristemic limit. This standalone program is designed to be user-friendly and accessible to all readers, without barriers. With only a few key parameters, including pH and temperature, this program provides a practical set of tools for comparing growth-related experimental data across various areas of plant biology. Additionally, it could be useful in predicting plant growth during assisted migration, particularly in the face of climate change. [ABSTRACT FROM AUTHOR]

【Objective】Tolerance to hypoxia germination is one of the key traits for direct-seeding adaptability of rice. The temperate direct-seeding japonica rice variety Francis and multi-panicle indica restorer line R998 were used for QTL mapping of hypoxia germination related traits, aiming to provide new valuable gene resources for developing direct-seeding rice varieties and the promotion of direct-seeding rice production methods.【Method】The coleoptile length, shoot length and maximum root length of rice seedlings submerged in 10-cm-depth water in the dark for 7 days at 28℃ were recorded as indicators of hypoxia germination tolerance capacity. A high-density genetic map containing 3 106 bin markers was constructed by low-coverage genome re-sequencing, and QTL scanning was performed with WinQTL Cart 2.5.【Result】Under the condition of hypoxia germination, the coleoptile length and root length of Francis are significantly higher than those of R998, but there is no significant difference in shoot length between them. The total genetic distance of the constructed genetic map is 3 646.2 cM, in which the number of markers on chromosome 12 is the least, and that on chromosome 1 is the most, with 174 and 389, respectively. The average marker distance in the genetic map is 1.21 cM, the marker distance of each chromosomes is 0.68 -1.84 cM, and the gaps above 5 cM account for 0.36%. By using composite interval mapping (CIM), six QTLs related to hypoxia germination tolerance are detected on 5 chromosomes. Among them, the number of QTLs controlling coleoptile length, shoot length and root length are 3, 1 and 2, respectively. The coleoptile locus qCL9 and the shoot length locus qSL5 had a phenotypic variance explained (PVE) over 10%, which are 13.39% and 10.78%, respectively. The beneficial allele of qCL9 and the root length locus qRL2-1 come from the parent Francis, while the other four beneficial alleles are provided by the parent R998. Three of the six QTLs have not been reported previously, therefore, they may be novel QTLs.【Conclusion】In summary, there is significant difference between Francis and R998 in hypoxia germination, and both parents have beneficial alleles for hypoxia germination tolerance. qCL9 and qSL5 are major effect QTLs controlling hypoxia germination tolerance and have practical value in the molecular breeding of direct-seeding rice.

Genetic modification of rice is mainly carried out by Agrobacterium-mediated transformation of callus accompanied by tissue culture. It is time consuming, laborious and unapplicable for cultivars unable to induce callus. In this study, we have reported a novel gene transfer protocol that involves pulling out primary leaf from coleoptile and injection of Agrobacterium culture into the empty channel. Out of 25 plants survived after injection of Agrobacterium tumefaciens EHA105 culture harboring pCAMBIA1301-RD29A-AtDREB1A, 8 T0 plants revealed the expected size of around 811 bp corresponding to AtDREB1A gene and Southern blotting analysis on 18 T1 plants suggested introgression of AtDREB1A. 3 T2 lines (7–9, 12–3, 18–6) exhibited accumulation of free proline and soluble sugars, yet increase of chlorophyll content, but decrease of electrolyte leakage and methane dicarboxylic aldehyde under cold stress condition at the vegetative growth stage. Yield components investigation on T2 lines showed earlier heading date and no yield loss compared to wild type plants grown under normal condition. GUS expression analysis and integrated transgene detection in T0 and T1 plants followed by evaluation of cold stress tolerance in T2 lines suggest the advantage of this in planta transformation protocol to obtain transgenic rice. [ABSTRACT FROM AUTHOR]

Summary: The green revolution was based on genetic modification of the gibberellin (GA) hormone system with "dwarfing" gene mutations that reduces GA signals, conferring shorter stature, thus enabling plant adaptation to modern farming conditions. Strong GA‐related mutants with shorter stature often have reduced coleoptile length, discounting yield gain due to their unsatisfactory seedling emergence under drought conditions. Here we present gibberellin (GA) 3‐oxidase1 (GA3ox1) as an alternative semi‐dwarfing gene in barley that combines an optimal reduction in plant height without restricting coleoptile and seedling growth. Using large‐scale field trials with an extensive collection of barley accessions, we showed that a natural GA3ox1 haplotype moderately reduced plant height by 5–10 cm. We used CRISPR/Cas9 technology, generated several novel GA3ox1 mutants and validated the function of GA3ox1. We showed that altered GA3ox1 activities changed the level of active GA isoforms and consequently increased coleoptile length by an average of 8.2 mm, which could provide essential adaptation to maintain yield under climate change. We revealed that CRISPR/Cas9‐induced GA3ox1 mutations increased seed dormancy to an ideal level that could benefit the malting industry. We conclude that selecting HvGA3ox1 alleles offers a new opportunity for developing barley varieties with optimal stature, longer coleoptile and additional agronomic traits. [ABSTRACT FROM AUTHOR]

【Objective】Tolerance to hypoxia germination is one of the key traits for direct-seeding adaptability of rice. The temperate direct-seeding japonica rice variety Francis and multi-panicle indica restorer line R998 were used for QTL mapping of hypoxia germination related traits, aiming to provide new valuable gene resources for developing direct-seeding rice varieties and the promotion of direct-seeding rice production methods.【Method】The coleoptile length, shoot length and maximum root length of rice seedlings submerged in 10-cm-depth water in the dark for 7 days at 28℃ were recorded as indicators of hypoxia germination tolerance capacity. A high-density genetic map containing 3 106 bin markers was constructed by low-coverage genome re-sequencing, and QTL scanning was performed with WinQTL Cart 2.5.【Result】Under the condition of hypoxia germination, the coleoptile length and root length of Francis are significantly higher than those of R998, but there is no significant difference in shoot length between them. The total genetic distance of the constructed genetic map is 3 646.2 cM, in which the number of markers on chromosome 12 is the least, and that on chromosome 1 is the most, with 174 and 389, respectively. The average marker distance in the genetic map is 1.21 cM, the marker distance of each chromosomes is 0.68 -1.84 cM, and the gaps above 5 cM account for 0.36%. By using composite interval mapping (CIM), six QTLs related to hypoxia germination tolerance are detected on 5 chromosomes. Among them, the number of QTLs controlling coleoptile length, shoot length and root length are 3, 1 and 2, respectively. The coleoptile locus qCL9 and the shoot length locus qSL5 had a phenotypic variance explained (PVE) over 10%, which are 13.39% and 10.78%, respectively. The beneficial allele of qCL9 and the root length locus qRL2-1 come from the parent Francis, while the other four beneficial alleles are provided by the parent R998. Three of the six QTLs have not been reported previously, therefore, they may be novel QTLs.【Conclusion】In summary, there is significant difference between Francis and R998 in hypoxia germination, and both parents have beneficial alleles for hypoxia germination tolerance. qCL9 and qSL5 are major effect QTLs controlling hypoxia germination tolerance and have practical value in the molecular breeding of direct-seeding rice. [ABSTRACT FROM AUTHOR]

Coleoptile, leaf, and root explants of the einkorn (Triticum monococcum ssp. monococcum) were cultured in vitro to obtain an efficient plant regeneration protocol through direct shoot formation by using different combinations and concentrations of various plant growth regulators. A total of 180 different auxin and cytokinin combinations were tested for regeneration. Shoot formation was not observed with the root and leaf explants. Shoot formation was obtained only from the coleoptile explants, with a mean of 1.20±0.24 shoots/explant and 86.60% of shoot formation frequency and with a 1.20±0.53 shoots/explant and 80.00% shoot formation frequency on medium supplemented with 0.5 mg L-1 TDZ and 1 mg L-1 TDZ plus 1 mg L-1 NAA, respectively. The shoots were subcultured on the MS medium containing the most effective hormonal combination concurrently continued to shoot and root formation for 45 days. It is noteworthy that 3.66±0.66 shoots per explant were induced by MS, which contained 1 mg L-1 TDZ plus 1 mg L-1 NAA and 2.0 mg L-1 KIN plus 0.5 mg L-1 NAA for 45 days. Of the different auxin concentrations tested for rooting, 2.0 mg L-1 IAA was predominant, with the greatest number of roots (12.33±0.88) produced per regenerated shoot. Finally, these well-developed plantlets were acclimatized with a 100% success rate and were transferred to the ex vitro conditions. A highly efficient regeneration protocol for einkorn wheat was developed using somatic tissue as an explant source for the first time.

Lead (Pb) is a widespread heavy metal pollutant that interferes with plant growth. In this study, we investigated the effects of Pb on the mechanical and chemical properties of cell walls and on the growth of coleoptiles of rice (Oryza sativa L.) seedlings grown in the air (on moistened filter paper) and underwater (submerged condition). Coleoptile growth of air-grown seedlings was reduced by 40% by the 3 mM Pb treatment, while that of water-grown ones was reduced by 50% by the 0.5 mM Pb. Although the effective concentration of Pb for growth inhibition of air-grown coleoptiles was much higher than that of water-grown ones, Pb treatment significantly decreased the mechanical extensibility of the cell wall in air- and water-grown coleoptiles, when it inhibited their growth. Among the chemical components of coleoptile cell walls, the amounts of cell wall polysaccharides per unit fresh weight and unit length of coleoptile, which represent the thickness of the cell wall, were significantly increased in response to the Pb treatment (3 mM and 0.5 mM Pb for air- and water-grown seedlings, respectively), while the levels of cell wall-bound diferulic acids (DFAs) and ferulic acids (FAs) slightly decreased. These results indicate that Pb treatment increased the thickness of the cell wall but not the phenolic acid-mediated cross-linking structures within the cell wall in air- and water-grown coleoptiles. The Pb-induced cell wall thickening probably causes the mechanical stiffening of the cell wall and thus decreases cell wall extensibility. Such modifications of cell wall properties may be associated with the inhibition of coleoptile growth. The results of this study provide a new finding that Pb-induced cell wall remodeling contributes to the regulation of plant growth under Pb stress conditions via the modification of the mechanical property of the cell wall. [ABSTRACT FROM AUTHOR]

Coleoptile is the small conical, short-lived, sheath-like organ that safeguards the first leaf and shoot apex in cereals. It is also the first leaf-like organ to senesce that provides nutrition to the developing shoot and is, therefore, believed to play a crucial role in seedling establishment in rice and other grasses. Though histochemical studies have helped in understanding the pattern of cell death in senescing rice coleoptiles, genome-wide expression changes during coleoptile senescence have not yet been explored. With an aim to investigate the gene regulation underlying the coleoptile senescence (CS), we performed a combinatorial whole genome expression analysis by sequencing transcriptome and miRNAome of senescing coleoptiles. Transcriptome analysis revealed extensive reprogramming of 3439 genes belonging to several categories, the most prominent of which encoded for transporters, transcription factors (TFs), signaling components, cell wall organization enzymes, redox homeostasis, stress response and hormone metabolism. Small RNA sequencing identified 41 known and 21 novel miRNAs that were differentially expressed during CS. Comparison of gene expression and miRNA profiles generated for CS with publicly available leaf senescence (LS) datasets revealed that the two aging programs are remarkably distinct at molecular level in rice. Integration of expression data of transcriptome and miRNAome identified high confidence 140 miRNA-mRNA pairs forming 42 modules, thereby demonstrating multi-tiered regulation of CS. The present study has generated a comprehensive resource of the molecular networks that enrich our understanding of the fundamental pathways regulating coleoptile senescence in rice. [ABSTRACT FROM AUTHOR]

Coleoptile is the small conical, short-lived, sheath-like organ that safeguards the first leaf and shoot apex in cereals. It is also the first leaf-like organ to senesce that provides nutrition to the developing shoot and is, therefore, believed to play a crucial role in seedling establishment in rice and other grasses. Though histochemical studies have helped in understanding the pattern of cell death in senescing rice coleoptiles, genome-wide expression changes during coleoptile senescence have not yet been explored. With an aim to investigate the gene regulation underlying the coleoptile senescence (CS), we performed a combinatorial whole genome expression analysis by sequencing transcriptome and miRNAome of senescing coleoptiles. Transcriptome analysis revealed extensive reprogramming of 3439 genes belonging to several categories, the most prominent of which encoded for transporters, transcription factors (TFs), signaling components, cell wall organization enzymes, redox homeostasis, stress response and hormone metabolism. Small RNA sequencing identified 41 known and 21 novel miRNAs that were differentially expressed during CS. Comparison of gene expression and miRNA profiles generated for CS with publicly available leaf senescence (LS) datasets revealed that the two aging programs are remarkably distinct at molecular level in rice. Integration of expression data of transcriptome and miRNAome identified high confidence 140 miRNA-mRNA pairs forming 42 modules, thereby demonstrating multi-tiered regulation of CS. The present study has generated a comprehensive resource of the molecular networks that enrich our understanding of the fundamental pathways regulating coleoptile senescence in rice.

Plants frequently experience hypoxia due to flooding caused by intensive rainfall or irrigation, when they are partially or completely submerged under a layer of water. In the latter case, some resistant plants implement a hypoxia avoidance strategy by accelerating shoot elongation, which allows lifting their leaves above the water surface. This strategy is achieved due to increased water uptake by shoot cells through water channels (aquaporins, AQPs). It remains a puzzle how an increased flow of water through aquaporins into the cells of submerged shoots can be achieved, while it is well known that hypoxia inhibits the activity of aquaporins. In this review, we summarize the literature data on the mechanisms that are likely to compensate for the decline in aquaporin activity under hypoxic conditions, providing increased water entry into cells and accelerated shoot elongation. These mechanisms include changes in the expression of genes encoding aquaporins, as well as processes that occur at the post-transcriptional level. We also discuss the involvement of hormones, whose concentration changes in submerged plants, in the control of aquaporin activity. [ABSTRACT FROM AUTHOR]

Somatic embryogenesis is in vitro culture propagation technique through cell division derived from plant parts to form embryos into new plants. BA and NAA application in media supported propagation in media to trigger callus formation. This research aimed to obtain the best concentration of BA and NAA combination to induce the callus of the Dendrobium Hybrid (Dendrobium lasianthera x Dendrobium antennatum) through somatic embryogenesis. It was conducted at the Laboratory of the Center for Development of Advanced Sciences and Technology (CDAST), the University of Jember East Java from March to September 2021. The research design used was CRD with two factors, the BA hormone factor at four levels, 0, 0.025, 0.05, and 0.1 mg L-1 and the NAA hormone at three levels, 1, 2, and 3 mg L-1. Results showed that callus formation of Dendrobium Hybrids was the fastest in the treatment of BA 0.025 mg L-1 and NAA 3 mg L-1, with the highest percentage of embryogenic callus at 67%. It showed that the addition of BA 0.025 mg L-1 and NAA 3 mg L-1 was the best result on the time of callus formation and the percentage of embryogenic callus. [ABSTRACT FROM AUTHOR]

Coleoptile, leaf, and root explants of the einkorn (Triticum monococcum ssp. monococcum) were cultured in vitro to obtain an efficient plant regeneration protocol through direct shoot formation by using different combinations and concentrations of various plant growth regulators. A total of 180 different auxin and cytokinin combinations were tested for regeneration. Shoot formation was not observed with the root and leaf explants. Shoot formation was obtained only from the coleoptile explants, with a mean of 1.20±0.24 shoots/explant and 86.60% of shoot formation frequency and with a 1.20±0.53 shoots/explant and 80.00% shoot formation frequency on medium supplemented with 0.5 mg L-1 TDZ and 1 mg L-1 TDZ plus 1 mg L-1 NAA, respectively. The shoots were subcultured on the MS medium containing the most effective hormonal combination concurrently continued to shoot and root formation for 45 days. It is noteworthy that 3.66±0.66 shoots per explant were induced by MS, which contained 1 mg L-1 TDZ plus 1 mg L-1 NAA and 2.0 mg L-1 KIN plus 0.5 mg L-1 NAA for 45 days. Of the different auxin concentrations tested for rooting, 2.0 mg L-1 IAA was predominant, with the greatest number of roots (12.33±0.88) produced per regenerated shoot. Finally, these well-developed plantlets were acclimatized with a 100% success rate and were transferred to the ex vitro conditions. A highly efficient regeneration protocol for einkorn wheat was developed using somatic tissue as an explant source for the first time. [ABSTRACT FROM AUTHOR]

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Flooding events caused by severe rains and poor soil drainage can interfere with plant germination and seedling establishment. Rice is one of the cereal crops that has unique germination strategies under flooding. One of these strategies is based on the fast coleoptile elongation in order to reach the water surface and re-establish the contact with the air. Microorganisms can contribute to plant health via plant growth promoters and provide protection from abiotic stresses. To characterise the community composition of the microbiome in rice germination under submergence, a 16S rRNA gene profiling metagenomic analysis was performed of temperate japonica rice varieties Arborio and Lamone seedlings, which showed contrasting responses in terms of coleoptile length when submerged. This analysis showed a distinct microbiota composition of Arborio seeds under submergence, which are characterised by the development of a long coleoptile. To examine the potential function of microbial communities under submergence, culturable bacteria were isolated, identified and tested for plant growth-promoting activities. A subgroup of isolated bacteria showed the capacity to hydrolyse starch and produce indole-related compounds under hypoxia. Selected bacteria were inoculated in seeds to evaluate their effect on rice under submergence, showing a response that is dependent on the rice genotype. Our findings suggest that endophytic bacteria possess plant growth-promoting activities that can substantially contribute to rice seedling establishment under submergence. [ABSTRACT FROM AUTHOR]

The wheat Green Revolution Rht-B1b and Rht-D1b dwarfing alleles are associated with increased grain yields but also with reduced early growth and seedling emergence, especially if sowing conditions are unfavourable. The gibberellic acid-responsive, mutagen-derived Rht18 dwarfing gene was backcrossed from durum wheat (Triticum turgidum subsp. durum L.) cv. Icaro into tall bread wheat (Triticum aestivum L.) cv. Halberd using phenotypic selection for reduced plant height. The Rht18 allele was confirmed among homozygous BC1F2-derived, F5:7 recombinant inbred lines by using a chromosome 6AS-linked, microsatellite molecular marker (Xwms4608), and then assessed for agronomic performance across multiple field sites ranging in yield from 3.6 to 6.4 t/ha. The Rht18-containing lines were significantly (P < 0.05) shorter in height (-24%) and reduced in plant lodging (-51%) compared with tall sister lines. Reductions in plant height were associated with significant increases in grain yield (+16%), reflecting increases in grain number (+21%), number of spikes (+7%) and number of grains per spike (+12%). Coleoptile length, early shoot biomass and ground cover percentage were unaffected by the presence of the Rht18 dwarfing gene. Comparisons of effects of gibberellic acid-insensitive Rht-B1b and Rht18 on early growth and agronomic performance were assessed separately for a set of 30 BC5F6-derived Halberd near-isogenic lines in the field in 2015. Ground cover and coleoptile length were significantly greater for Rht18 lines, whereas plant height, lodging, harvest index, grain number and yield were similar for Rht-B1b and Rht18 sister lines. Reduced lodging and increased grain number and yield, together with greater coleoptile length, indicate a potentially useful role for Rht18 in improving wheat performance. [ABSTRACT FROM AUTHOR]

Flooding events caused by severe rains and poor soil drainage can interfere with plant germination and seedling establishment. Rice is one of the cereal crops that has unique germination strategies under flooding. One of these strategies is based on the fast coleoptile elongation in order to reach the water surface and re-establish the contact with the air. Microorganisms can contribute to plant health via plant growth promoters and provide protection from abiotic stresses. To characterise the community composition of the microbiome in rice germination under submergence, a 16S rRNA gene profiling metagenomic analysis was performed of temperate japonica rice varieties Arborio and Lamone seedlings, which showed contrasting responses in terms of coleoptile length when submerged. This analysis showed a distinct microbiota composition of Arborio seeds under submergence, which are characterised by the development of a long coleoptile. To examine the potential function of microbial communities under submergence, culturable bacteria were isolated, identified and tested for plant growth-promoting activities. A subgroup of isolated bacteria showed the capacity to hydrolyse starch and produce indole-related compounds under hypoxia. Selected bacteria were inoculated in seeds to evaluate their effect on rice under submergence, showing a response that is dependent on the rice genotype. Our findings suggest that endophytic bacteria possess plant growth-promoting activities that can substantially contribute to rice seedling establishment under submergence.

Abstract Background In Asian rice production, an increasing number of countries now choose the direct seeding mode because of rising costs, labour shortages and water shortages. The ability of rice seeds to undergo anaerobic germination (AG) plays an important role in the success of direct seeding. Results In this study, we used 2,123,725 single nucleotide polymorphism (SNP) markers based on resequencing to conduct a dynamic genome-wide association study (GWAS) of coleoptile length (CL) and coleoptile diameter (CD) in 209 natural rice populations. A total of 26 SNP loci were detected in these two phenotypes, of which 5 overlapped with previously reported loci (S1_ 39674301, S6_ 20797781, S7_ 18722403, S8_ 9946213, S11_ 19165397), and two sites were detected repeatedly at different time points (S3_ 24689629 and S5_ 27918754). We suggest that these 7 loci (−log10 (P) value > 7.3271) are the key sites that affect AG tolerance. To screen the candidate genes more effectively, we sequenced the transcriptome of the flooding-tolerant variety R151 in six key stages, including anaerobic (AN) and the oxygen conversion point (AN-A), and obtained high-quality differential expression profiles. Four reliable candidate genes were identified: Os01g0911700 (OsVP1), Os05g0560900 (OsGA2ox8), Os05g0562200 (OsDi19–1) and Os06g0548200. Then qRT-PCR and LC-MS/ MS targeting metabolite detection technology were used to further verify that the up-regulated expression of these four candidate genes was closely related to AG. Conclusion The four novel candidate genes were associated with gibberellin (GA) and abscisic acid (ABA) regulation and cell wall metabolism under oxygen-deficiency conditions and promoted coleoptile elongation while avoiding adverse effects, allowing the coleoptile to obtain oxygen, escape the low-oxygen environment and germinate rapidly. The results of this study improve our understanding of the genetic basis of AG in rice seeds, which is conducive to the selection of flooding-tolerant varieties suitable for direct seeding.

Lead (Pb) is a widespread heavy metal pollutant that interferes with plant growth. In this study, we investigated the effects of Pb on the mechanical and chemical properties of cell walls and on the growth of coleoptiles of rice (Oryza sativa L.) seedlings grown in the air (on moistened filter paper) and underwater (submerged condition). Coleoptile growth of air-grown seedlings was reduced by 40% by the 3 mM Pb treatment, while that of water-grown ones was reduced by 50% by the 0.5 mM Pb. Although the effective concentration of Pb for growth inhibition of air-grown coleoptiles was much higher than that of water-grown ones, Pb treatment significantly decreased the mechanical extensibility of the cell wall in air- and water-grown coleoptiles, when it inhibited their growth. Among the chemical components of coleoptile cell walls, the amounts of cell wall polysaccharides per unit fresh weight and unit length of coleoptile, which represent the thickness of the cell wall, were significantly increased in response to the Pb treatment (3 mM and 0.5 mM Pb for air- and water-grown seedlings, respectively), while the levels of cell wall-bound diferulic acids (DFAs) and ferulic acids (FAs) slightly decreased. These results indicate that Pb treatment increased the thickness of the cell wall but not the phenolic acid-mediated cross-linking structures within the cell wall in air- and water-grown coleoptiles. The Pb-induced cell wall thickening probably causes the mechanical stiffening of the cell wall and thus decreases cell wall extensibility. Such modifications of cell wall properties may be associated with the inhibition of coleoptile growth. The results of this study provide a new finding that Pb-induced cell wall remodeling contributes to the regulation of plant growth under Pb stress conditions via the modification of the mechanical property of the cell wall.

Long coleoptile (LC) - wheat genotypes sown deeper (> 10 cm) than current practice (< 5 cm) enables earlier deep sowing into subsurface soil moisture. The LC genotype shows promise to broaden sowing windows and remove reliance on the shifting seasonal break for crop establishment. The suitability of this sowing strategy to the highly variable soils of the southern Australian wheatbelt warrants investigation to identify suitable environments for potential establishment benefits. We conducted controlled environment room (CER) and field experiments using pairs of near-isogenic-lines (NILs) that differed genetically only for coleoptile length. The experiments investigated the suitability of deep sown (12 cm) LC wheats in soils with different texture (sand versus loam). The CER experiment identified that LC genotypes exhibited greater emergence and early seedling growth, producing greater shoot and root biomass, when deep sown (12 cm) in loam. While LC and short coleoptile (SC) genotypes produced similar shoot growth when sown at depth in sand, LC produced greater root biomass reflected in more seminal roots. In the field on sand, LC and SC had similar emergence and early shoot growth characteristics at all sowing depths (5, 8 and 10 cm). However, the heavy-textured, loam soil reduced seedling emergence and restricted leaf growth with deep sowing (12 cm) in the SC. Our results indicate that the LC trait was more critical for plant emergence and early growth parameters (shoot and root biomass) from depth in a heavier textured loam compared with a sand. By identifying environments that will likely benefit most from deep sown LC, we are one step closer to adapting crop production to shifting rainfall patterns in southern Australia.

Cover crop use in organic rice cropping systems efficiently manages the two most limiting factors in organic agriculture - weed competition and nutrient availability. Nonetheless, cover crop biomasses on soil surfaces under the anaerobic conditions in flooded rice systems produce organic acids (mainly acetic acid) that cause early phytotoxicity to rice seedling coleoptile and roots. This study evaluated the dose-response of acetic acid on germination rates and post-germination growth traits (coleoptile, first leaf, and roots). Under controlled conditions, the seeds of three rice varieties (Sant'Andrea, Salvo, and Selenio) were immersed in acetic acid concentrations (0, 9, 18, 36, 54, and 72 ppm) for eight days. Germination results suggest that acetic acid likely scarred var. Salvo, based on a 15% faster germination rate compared to untreated controls. Across all varieties, increased acetic acid never slowed germination. During post-germination growth stages, root phytotoxicity was always more evident than shoot phytotoxicity, although the responses varied among the varieties. Root length damage appeared first at acetic acid concentrations of 36 ppm in var. Sant'Andrea and Selenio, and at 54 ppm in var. Salvo. Root length measurements provided explicit and speedy information on varietal tolerance to acetic acid and, consequently to cover crop fermentation and suggested that direct observation of root damage in paddy fields is valuable for prompt water management decisions, such as flooding interruption. Further development of this method may lead to more complete varietal screening and identification of related genetic traits responsible for tolerance. [ABSTRACT FROM AUTHOR]

Cover crop use in organic rice cropping systems efficiently manages the two most limiting factors in organic agriculture - weed competition and nutrient availability. Nonetheless, cover crop biomasses on soil surfaces under the anaerobic conditions in flooded rice systems produce organic acids (mainly acetic acid) that cause early phytotoxicity to rice seedling coleoptile and roots. This study evaluated the dose-response of acetic acid on germination rates and post-germination growth traits (coleoptile, first leaf, and roots). Under controlled conditions, the seeds of three rice varieties (Sant’Andrea, Salvo, and Selenio) were immersed in acetic acid concentrations (0, 9, 18, 36, 54, and 72 ppm) for eight days. Germination results suggest that acetic acid likely scarred var. Salvo, based on a 15% faster germination rate compared to untreated controls. Across all varieties, increased acetic acid concentrations never slowed germination. During post-germination growth stages, root phytotoxicity was always more evident than shoot phytotoxicity, although the responses varied among the varieties. Root length damage appeared first at acetic acid concentrations of 36 ppm in var. Sant’Andrea and Selenio, and at 54 ppm in var. Salvo. Root length measurements provided explicit and speedy information on varietal tolerance to acetic acid and, consequently to cover crop fermentation and suggested that direct observation of root damage in paddy fields is valuable for prompt water management decisions, such as flooding interruption. Further development of this method may lead to more complete varietal screening and identification of related genetic traits responsible for tolerance. Highlights - Based on genotype, increasing acetic acid levels in flooding waters can speed rice germination. - Roots are more sensitive than shoots to acetic acid phytotoxicity during very early germination. - Early root length impairments provide information on tolerance to acetic acid phytotoxicity. - A slower germination rate may induce higher tolerance to green mulching.

The cost-effective production of biofuels from lignocellulosic material will likely require manipulation of plant biomass, specifically cell walls. The North American native prairie grass Panicum virgatum (switchgrass) is seen as a potential biofuel crop with an array of genetic resources currently being developed. We have characterized the endomembrane proteome of switchgrass coleoptiles to provide additional information to the switchgrass community. In total, we identified 1750 unique proteins from two biological replicates. These data have been deposited in the ProteomeXchange with the identifier PXD001351 (http://proteomecentral.proteomexchange.org/dataset/PXD001351).

Plants frequently experience hypoxia due to flooding caused by intensive rainfall or irrigation, when they are partially or completely submerged under a layer of water. In the latter case, some resistant plants implement a hypoxia avoidance strategy by accelerating shoot elongation, which allows lifting their leaves above the water surface. This strategy is achieved due to increased water uptake by shoot cells through water channels (aquaporins, AQPs). It remains a puzzle how an increased flow of water through aquaporins into the cells of submerged shoots can be achieved, while it is well known that hypoxia inhibits the activity of aquaporins. In this review, we summarize the literature data on the mechanisms that are likely to compensate for the decline in aquaporin activity under hypoxic conditions, providing increased water entry into cells and accelerated shoot elongation. These mechanisms include changes in the expression of genes encoding aquaporins, as well as processes that occur at the post-transcriptional level. We also discuss the involvement of hormones, whose concentration changes in submerged plants, in the control of aquaporin activity.

Abstract Since Charles Darwin discovered growth movements of the shoot tip (coleoptile) toward light, the grass coleoptiles have long been used as a model system to study plant growth. Rapid growth of the coleoptile is vital for successful seed germination and early seedling establishment. However, the proteome changes underlying the rapid growth of the coleoptiles are not yet clear in the model plant maize (Zea mays). In the present study, we investigated proteome changes in vivo occurring in the rapidly growing coleoptiles of maize with two‐dimensional gel electrophoresis combined with mass spectrometry. A quantitative comparison of the proteomes at 1.5, 3, and 5 days after germination showed significant changes in protein profiles with coleoptile growth. As a result, 31 differential abundance proteins (DAPs) representing 44 protein spots were identified, of which 21 DAPs with increased abundances were implied in growth‐related processes, including translational initiation, transcription regulation, protein and other compound synthesis, H+‐transmembrane transport and cytoskeleton organization. The selected DAPs were confirmed by reverse transcription quantitative PCR and immunoblot analysis. We suggested that the rapid growth of the coleoptile is largely due to its ability to quickly enhance relevant cellular processes, especially the increased synthesis of the growth‐related DAPs. The content of indole‐3‐acetic acid, salicylic acid, and jasmonic acid decreased significantly, and the content of gibberellins first decreased and then increased during the elongation of coleoptile. This study provides new insight into the significance of proteome changes in coleoptile growth.

Since Charles Darwin discovered growth movements of the shoot tip (coleoptile) toward light, the grass coleoptiles have long been used as a model system to study plant growth. Rapid growth of the coleoptile is vital for successful seed germination and early seedling establishment. However, the proteome changes underlying the rapid growth of the coleoptiles are not yet clear in the model plant maize (Zea mays). In the present study, we investigated proteome changes in vivo occurring in the rapidly growing coleoptiles of maize with two‐dimensional gel electrophoresis combined with mass spectrometry. A quantitative comparison of the proteomes at 1.5, 3, and 5 days after germination showed significant changes in protein profiles with coleoptile growth. As a result, 31 differential abundance proteins (DAPs) representing 44 protein spots were identified, of which 21 DAPs with increased abundances were implied in growth‐related processes, including translational initiation, transcription regulation, protein and other compound synthesis, H+‐transmembrane transport and cytoskeleton organization. The selected DAPs were confirmed by reverse transcription quantitative PCR and immunoblot analysis. We suggested that the rapid growth of the coleoptile is largely due to its ability to quickly enhance relevant cellular processes, especially the increased synthesis of the growth‐related DAPs. The content of indole‐3‐acetic acid, salicylic acid, and jasmonic acid decreased significantly, and the content of gibberellins first decreased and then increased during the elongation of coleoptile. This study provides new insight into the significance of proteome changes in coleoptile growth. [ABSTRACT FROM AUTHOR]

Responses of rice seedlings to UV‐B radiation (UV‐B) were investigated, aiming to establish rice as a model plant for UV‐B signalling studies. The growth of japonica rice coleoptiles, grown under red light, was inhibited by brief irradiation with UV‐B, but not with blue light. The effective UV‐B fluences (10−1‐103 μmol m−2) were much lower than those reported in Arabidopsis. The response was much less in indica rice cultivars and its extent varied among Oryza species. We next identified UV‐B‐specific anthocyanin accumulation in the first leaf of purple rice and used this visible phenotype to isolate mutants. Some isolated mutants were further characterized, and one was found to have a defect in the growth response. Using microarrays, we identified a number of genes that are regulated by low‐fluence‐rate UV‐B in japonica coleoptiles. Some up‐regulated genes were analysed by real‐time PCR for UV‐B specificity and the difference between japonica and indica. More than 70% of UV‐B‐regulated rice genes had no homologs in UV‐B‐regulated Arabidopsis genes. Many UV‐B‐regulated rice genes are related to plant hormones and especially to jasmonate biosynthetic and responsive genes in apparent agreement with the growth response. Possible involvement of two rice homologs of UVR8, a UV‐B photoreceptor, is discussed. Rice responds to UV‐B, as seen in coleoptile growth inhibition, much more sensitively than Arabidopsis and with UV‐B‐regulated genes largely different from Arabidopsis ones. UV‐B response mutants can be isolated from purple rice. Rice will serve as a new model plant for UV‐B signalling studies. [ABSTRACT FROM AUTHOR]

Abstract Background Good establishment is important for rapid leaf area development in wheat crops. Poor establishment results in fewer, later-emerging plants, reduced leaf area and tiller number. In addition, poorly established crops suffer from increased soil moisture loss through evaporation and greater competition from weeds while fewer spikes are produced which can reduce grain yield. By protecting the emerging first leaf, the coleoptile is critical for achieving good establishment, and its length and interaction with soil physical properties determine the ability of a cultivar to emerge from depth. Results Here we characterise a locus on chromosome 1AS, that increases coleoptile length in wheat, which we designate as Lcol-A1. We identified Lcol-A1 by bulked-segregant analysis and used a Halberd-derived population to fine map the gene to a 2 cM region, equivalent to 7 Mb on the IWGSC genome reference sequence of Chinese Spring (RefSeqv1.0). By sowing recently released cultivars and near-isogenic lines in the field at both conventional and deep sowing depths, we confirmed that Locl-A1 was associated with increased emergence from depth in the presence and absence of conventional dwarfing genes. Flanking markers IWB58229 and IWA710 were developed to assist breeders to select for long coleoptile wheats. Conclusions Increased coleoptile length is sought in many global wheat production areas to improve crop emergence. The identification of the gene Lcol-A1, together with tools to allow wheat breeders to track the gene, will enable improvements to be made for this important trait.

Early seedling growth, including seedling emergence and vigor, is crucial in direct seeded rice. In this study, we examined the effects of gibberellic acid (GA3) and ethephon (ET) on the early growth of direct seeded rice, and on α-amylase activity and soluble sugar content in the seeds. Rice seeds were treated with water (control), ET, GA3, or ET+ GA3 and were allowed to grow for 21 days. The results showed that ET and GA3 synergistically improved the lengths of mesocotyl, coleoptile, mesocotyl+ coleoptile, and first leaf. Moderate synergistic effects of ET and GA3 were detected in the second and third leaves. ET+ GA3 treatment induced higher α-amylase activities during early post-germination growth, which is consistent with the longer coleoptile, mesocotyl, mesocotyl+ coleoptile, and first leaf. In addition, ET+ GA3 induced higher α-amylase activity in the seeds, and consequently, higher sucrose and glucose concentrations than other treatments. These results partially explain the regulatory mechanism underlying the synergistic interaction of ET and GA3 on rice seedling growth in terms of starch and sugar metabolism in the seeds, and this knowledge is expected to facilitate the practical use of ET and GA3 in direct seeded rice systems.

Einkorn indirect shoot regeneration was obtained from leaf, coleoptile, and root explants cultured on full, ½, and ¼ strength Murashige and Skoog (MS) medium containing 0.5 to 10 mg L−1 2,4-dichlorophenoxyacetic acid (2,4-D). Calluses derived from coleoptile and root explants were cultured on full-strength MS medium supplemented with 0.5 to 5 mg L−1 thidiazuron (TDZ) for 6 wk to induce plant regeneration. Only callus cultures derived from coleoptile explants regenerated shoots. For root induction, 1.0 to 10 mg L−1 indole-3-acetic acid (IAA) was used for 4 wk. The highest rate of callus formation (93%) was from root explants cultured on full-strength MS medium with 4 mg L−1 2,4-D. Coleoptile explants had the highest callus formation (100%) after culture on full-strength MS medium with 3 to 6 mg L−1 of 2,4-D. The highest indirect shoot regeneration (7.0 ± 1.1 shoots produced per callus with a 67% shoot formation frequency) was from calluses derived from coleoptile explant cultured on full MS medium supplemented with 5 mg L−1 of TDZ. Of the different IAA concentrations investigated for rooting, the greatest number of roots per explant (7.7 ± 0.088 roots produced per regenerated shoot with a 100% root formation frequency) was observed on MS medium supplemented with 6 mg L−1 IAA. This indirect shoot regeneration protocol for coleoptile-derived einkorn wheat callus will be useful for future wheat genetic and improvement studies. [ABSTRACT FROM AUTHOR]

Background: In Asian rice production, an increasing number of countries now choose the direct seeding mode because of rising costs, labour shortages and water shortages. The ability of rice seeds to undergo anaerobic germination (AG) plays an important role in the success of direct seeding. Results: In this study, we used 2,123,725 single nucleotide polymorphism (SNP) markers based on resequencing to conduct a dynamic genome-wide association study (GWAS) of coleoptile length (CL) and coleoptile diameter (CD) in 209 natural rice populations. A total of 26 SNP loci were detected in these two phenotypes, of which 5 overlapped with previously reported loci (S1_ 39674301, S6_ 20797781, S7_ 18722403, S8_ 9946213, S11_ 19165397), and two sites were detected repeatedly at different time points (S3_ 24689629 and S5_ 27918754). We suggest that these 7 loci (−log10 (P) value > 7.3271) are the key sites that affect AG tolerance. To screen the candidate genes more effectively, we sequenced the transcriptome of the flooding-tolerant variety R151 in six key stages, including anaerobic (AN) and the oxygen conversion point (AN-A), and obtained high-quality differential expression profiles. Four reliable candidate genes were identified: Os01g0911700 (OsVP1), Os05g0560900 (OsGA2ox8), Os05g0562200 (OsDi19–1) and Os06g0548200. Then qRT-PCR and LC-MS/ MS targeting metabolite detection technology were used to further verify that the up-regulated expression of these four candidate genes was closely related to AG. Conclusion: The four novel candidate genes were associated with gibberellin (GA) and abscisic acid (ABA) regulation and cell wall metabolism under oxygen-deficiency conditions and promoted coleoptile elongation while avoiding adverse effects, allowing the coleoptile to obtain oxygen, escape the low-oxygen environment and germinate rapidly. The results of this study improve our understanding of the genetic basis of AG in rice seeds, which is conducive to the selection of flooding-tolerant varieties suitable for direct seeding. [ABSTRACT FROM AUTHOR]

Summary: Rice coleoptile elongation under submergence guarantees fast seedling establishment in the field. We investigated the role of auxin in influencing the capacity of rice to produce a long coleoptile under water.In order to explore the complexity of auxin's role in coleoptile elongation, we used gene expression analysis, confocal microscopy of an auxin‐responsive fluorescent reporter, gas chromatography coupled to tandem mass spectrometry (GC–MS/MS), and T‐DNA insertional mutants of an auxin transport protein.We show that a higher auxin availability in the coleoptile correlates with the final coleoptile length under submergence. We also identified the auxin influx carrier AUX1 as a component influencing this trait under submergence. The coleoptile tip is involved in the final length of rice varieties harbouring a long coleoptile.Our experimental results indicate that auxin biosynthesis and transport underlies the differential elongation between short and long coleoptile‐harbouring japonica rice varieties. See also the Editorial on this article by Sasidharan et al., 229: 5–7. [ABSTRACT FROM AUTHOR]

Summary: Most crops cannot germinate underwater. Rice exhibits certain degrees of tolerance to oxygen deficiency for anaerobic germination (AG) and anaerobic seedling development (ASD). Direct rice seeding, whereby seeds are sown into soil rather than transplanting seedlings from the nursery, becomes an increasingly popular cultivation method due to labor shortages and opportunities for sustainable cultivation. Flooding is common under direct seeding, but most rice varieties have poor capability of AG/ASD, which is a major obstacle to broad adoption of direct seeding. A better understanding of the physiological basis and molecular mechanisms regulating AG/ASD should facilitate rice breeding for enhanced seedling vigor under flooding. This review highlights recent advances on molecular and physiological mechanisms and future breeding strategies of rice AG/ASD. See also the Editorial on this article by Sasidharan et al., 229: 5–7. [ABSTRACT FROM AUTHOR]

Copyright of Harran Journal of Agricultural & Food Science is the property of Harran University, Faculty of Agriculture 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.)

Copyright of Journal of Agricultural Science & Technology (1008-0864) is the property of Journal of Agricultural Science & Technology 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.)

From the perspective of wheat yield improvement, the coleoptile is vital for successful crop establishment, and long coleoptile lengths (CLs) are preferred in wheat-growing regions where deep planting is practiced. To determine the genetic basis of CL, we performed a genome-wide association study on a set of 707 Chinese wheat landraces using 18,594 single-nucleotide polymorphisms and 38,678 diversity array technology sequencing markers. We accordingly detected a total of 29 significant markers [−log10(P) > 4.76] distributed on chromosomes 2B, 2D, 3A, 4A, 5A, 6A, 6B, 6D, and 7B. Based on linkage disequilibrium decay distance, we identified a total of 17 quantitative trait loci associated with CL, among which QCl.sicau-6B.2, located at 508.17–509.26 Mb on chromosome 6B, was recognized as a novel major locus. We subsequently developed a high-resolution melt marker for QCl.sicau-6B.2, which was validated in an F2:3 population. Our findings provide important insights into the genetic mechanisms underlying coleoptile growth and could be applied to marker-assisted wheat selection.

In South Asia, including Bangladesh, most farmers sow wheat under residual soil moisture after rice is harvested, but the upper layer of soil dries quickly after soil has been prepared for wheat sowing. Crop seeds that are sown either deeply or shallowly can result in failed emergence, low dry matter accumulation, and reduced grain yield. Therefore, appropriate sowing depth is crucial for seedling emergence and successful crop establishment. Considering this, a two-year field experiment was conducted at the research field of the Agricultural Research Station of the Bangladesh Agricultural Research Institute at Dinajpur during the dry, rabi (winter) season of 2013-14 and 2014-15, at four sowing depths, i.e., 2, 4, 6 and 8 cm, to identify the most appropriate sowing depth for higher grain yield. Wheat seeds sown at a depth of 4 cm resulted in significantly highest number of seedlings and seminal roots, tallest plants as well as largest roots and plant biomass followed by sowing at a depth of 6, or 2 cm. Depth of sowing also significantly affected the yield and yield-related attributes, all performing best at a depth of 4 cm. The highest number of spikes m-2, grain yield, straw yield and harvest index were observed when seeds were sown at depths of 4 or 6 cm, relative to 2 or 8 cm. Therefore, a sowing depth of 4 to 6 cm is recommended for wheat cultivation in South Asia, including Northern Bangladesh.

The high growth-stimulating effect of plant extract has urged the plant biotechnologists to use natural supplements in the culture media instead of synthetic phytohormones. We advocated the effect of sprouted sorghum extract (SSE) on emergence, in vitro acclimatization, and genetic fidelity in coleoptile derived callus of indica rice variety ADT36. The use of SSE with Murashige Skoog medium efficiently acclimatized the root and shoot apical systems. A higher mat and seminal roots (3.4 g biomass) with an efficient shoot primordium elongation were observed with an increase in the concentration of SSE. Seeds treated with SSE medium showed higher germination and earlier coleoptile maturation about 48 h compared to untreated seeds, and there was a higher expression of eEF-1α with an increase in coleoptile length. B5 medium was effective on inducing embryogenic and nodular callus from 3-day-old coleoptile with 3.0 mg/L 2,4-dichlorophenoxyacetic acid and further proliferated effectively with 0.8 mg/L kinetin with a fresh weight of 180 mg. Highly significant regeneration was observed with combination of 2.5 mg/L 6-benzylamino purine and 3.0 mg/L α-naphthaleneacetic acid. The metabolic and genetic profiles of in vitro and directly cultivated plants were the same, examined through Fourier-transform infrared spectroscopy, random amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR) and R-ISSR (combination of RAPD and ISSR) markers, respectively, and thus confirming the significant efficacy of the SSE incorporated medium. Disarmed T-DNA was transformed to coleoptile derived callus through Agrobacterium tumefaciens LBA4404 and confirmed by GUS assay. The T-DNA integration was confirmed by DNA blot analysis using DNA from transient GUS-expressed explants. Thus, SSE can be used as a natural and organic supplement for organogenesis and efficient acclimatizations of shoot and root apical meristems in regenerated plants.

Turgor maintenance through osmotic adjustment can play a vital role in plant tolerance to drought and salinity. As per the evidence of the previous study, chemical polyethylene glycol (PEG) can create physiological drought under both salinity and water deficit conditions. Therefore, PEG is used for forcefully create osmotic stress to find out drought and salinity resistant crop cultivars at the early stage. Considering the essential role of PEG, the current observation was undertaken for understanding the effects of drought and salinity stress on several bread wheat genotypes at early developmental stage particularly during the seedling stage. Five bread wheat genotypes including four varieties such as 'Tekirdag', 'Ceyhan 99', 'Dinc', 'Empire Plus' and a line 'DZ17-1' were used as seed material. To find out the genotypes which are tolerant to drought and salinity, all wheat genotypes were evaluated in four different concentration of NaCl for salinity stress (i.e., 0, 4, 8 and 12 dS/m) and four different concentration of PEG 6000 (i.e., 0, -0.2, -0.4, -0.6 MPa) for drought stress. All treatments were organised in a completely randomized design (CRD) and repeated three times. After observation, it is revealed that bread wheat cultivars 'Dinc' and 'Ceyhan 99' were found tolerant of both drought and salinity stress at the seedling stage. The study also noticed that understanding of seedlings growth such as mean germination time (MGT), coleoptile length, seedling height, root length and relative water content (RWC) allow the selection of genotypes tolerance to drought and salinity. The information from the study will be helpful for examination of wheat genotypes which are suitable to cultivate under osmotic stress of both drought and salinity stress condition. [ABSTRACT FROM AUTHOR]

Regulation of plant height and stem elongation has contributed significantly to improvement of cereal productivity by reducing lodging and improving distribution of assimilates to the inflorescence and grain. In wheat, genetic control of height has been largely contributed by the Reduced height-1 alleles that confer gibberellin insensitivity; the beneficial effects of these alleles are associated with less favourable effects involving seedling emergence, grain quality, and inflorescence architecture that have driven new research investigating genetic variation of stem growth. Here, we show that TEOSINTE BRANCHED1 (TB1) regulates height of wheat, with TB1 being expressed at low levels in nodes of the main culm prior to elongation, and increased dosage of TB1 restricting elongation of stem internodes. The effect of TB1 on stem growth is not accompanied by poor seedling emergence, as transgenic lines with increased activity of TB1 form longer coleoptiles than null transgenic controls. Analysis of height in a multiparent mapping population also showed that allelic variation for TB1 on the B genome influences height, with plants containing the variant TB-B1b allele being taller than those with the wild-type TB-B1a allele. Our results show that TB1 restricts height and stem elongation in wheat, suggesting that variant alleles that alter the expression or function of TB1 could be used as a new source of genetic diversity for optimizing architecture of wheat in breeding programmes. [ABSTRACT FROM AUTHOR]

From the perspective of wheat yield improvement, the coleoptile is vital for successful crop establishment, and long coleoptile lengths (CLs) are preferred in wheat-growing regions where deep planting is practiced. To determine the genetic basis of CL, we performed a genome-wide association study on a set of 707 Chinese wheat landraces using 18,594 single-nucleotide polymorphisms and 38,678 diversity array technology sequencing markers. We accordingly detected a total of 29 significant markers [−log10(P) > 4.76] distributed on chromosomes 2B, 2D, 3A, 4A, 5A, 6A, 6B, 6D, and 7B. Based on linkage disequilibrium decay distance, we identified a total of 17 quantitative trait loci associated with CL, among which QCl.sicau-6B.2 , located at 508.17–509.26 Mb on chromosome 6B, was recognized as a novel major locus. We subsequently developed a high-resolution melt marker for QCl.sicau-6B.2 , which was validated in an F 2:3 population. Our findings provide important insights into the genetic mechanisms underlying coleoptile growth and could be applied to marker-assisted wheat selection. [ABSTRACT FROM AUTHOR]

This study aimed to gain insights into the molecular mechanisms underlying the role of ethylene in regulating germination and seedling growth in wheat by combining pharmacological, molecular, and metabolomics approaches. Our study showed that ethylene does not affect radicle protrusion but controls post-germination endospermic starch degradation through transcriptional regulation of specific α-amylase and α-glucosidase genes, and this effect is mediated by alteration of endospermic bioactive gibberellin (GA) levels, and GA sensitivity via expression of the GA signaling gene, TaGAMYB. Our data implicated ethylene as a positive regulator of embryo axis and coleoptile growth through transcriptional regulation of specific TaEXPA genes. These effects were associated with modulation of GA levels and sensitivity, through expression of GA metabolism (TaGA20ox1 , TaGA3ox2 , and TaGA2ox6) and signaling (TaGAMYB) genes, respectively, and/or the abscisic acid (ABA) level and sensitivity, via expression of specific ABA metabolism (TaNCED2 or TaCYP707A1) and signaling (TaABI3) genes, respectively. Ethylene appeared to regulate the expression of TaEXPA3 and thereby root growth through its control of coleoptile ABA metabolism, and root ABA signaling via expression of TaABI3 and TaABI5. These results show that spatiotemporal modulation of ABA/GA balance mediates the role of ethylene in regulating post-germination storage starch degradation and seedling growth in wheat. [ABSTRACT FROM AUTHOR]

Susceptibility of sorghum seedlings to infection by Sporisorium sorghi, the fungus causing covered kernel smut (CKS) disease, is limited to the period between the sowing of the seed and emergence of the seedling. Microscopy and PCR diagnosis of 7-day-old infected seedlings detected hyphae of S. sorghi in plumule and mesocotyl tissue but not in coleoptile and radicle tissue. Percent infected seedling plumule and mesocotyl tissue detected by microscopy and PCR corresponded well to field resistance classes for CKS in mature panicles of both sorghums tested with Giza-15 being highly susceptible and hybrid Shandweel-305 being resistant. Bulk extracts of phenolics and antioxidants from seedling plumule and mesocotyl tissues of hybrid Shandweel-305 cv significantly inhibited the in vitro mycelial growth of S. sorghi more than those from Giza-15 cv. Moreover, bulk extracts of plumule and mesocotyl tissue of seedlings grown from seed inoculated with S. sorghi teliospores contained higher phenolic and antioxidant content in the resistant hybrid (Shandweel-305) than the highly susceptible cultivar (Giza-15). Similarly, bulk extracts of plumule and mesocotyl tissue of 7-day-old seedlings grown from seed inoculated with S. sorghi teliospores contained higher phenolic and antioxidant content in the resistant hybrid (Shandweel-305) than the highly susceptible cultivar (Giza-15). Ferulic, isorhamnetin and kaempferol acids were detected only in plumule and mesocotyl tissue of resistant hybrid Shandweel-305, whereas ellagic, fumaric and vanillic acids were detected only in highly susceptible Giza-15 cv. Ferulic acid added to malt dextrose broth medium significantly inhibited in vitro teliospore germination and mycelial growth of S. sorghi, especially when added at the highest concentrations. This research established that the mode of seedling infection of sorghum by S. sorghi is almost exclusively through the plumule and mesocotyl tissue. Within these tissues, the presence of the pathogen can induce host production of phenolics, including the fungitoxic ferulic acid and antioxidants at higher concentrations within the resistant sorghum than in the highly susceptible cultivar. [ABSTRACT FROM AUTHOR]

Phototropin1 (phot1) perceives low- to high-fluence blue light stimuli and mediates both the first and second positive phototropisms. High-fluence blue light is known to induce autophosphorylation of phot1, leading to the second positive phototropism. However, the phosphorylation status of phot1 by low-fluence blue light that induces the first positive phototropism had not been observed. Here, we conducted a phosphoproteomic analysis of maize coleoptiles to investigate the fluence-dependent phosphorylation status of Zmphot1. High-fluence blue light induced phosphorylation of Zmphot1 at several sites. Notably, low-fluence blue light significantly increased the phosphorylation level of Ser291 in Zmphot1. Furthermore, Ser291-phosphorylated and Ser369Ser376-diphosphorylated peptides were found to be more abundant in the low-fluence blue light-irradiated sides than in the shaded sides of coleoptiles. The roles of these phosphorylation events in phototropism were explored by heterologous expression of ZmPHOT1 in the Arabidopsis thaliana phot1phot2 mutant. The first positive phototropism was restored in wild-type ZmPHOT1 -expressing plants; however, plants expressing S291A-ZmPHOT1 or S369AS376A-ZmPHOT1 showed significantly reduced complementation rates. All transgenic plants tested in this study exhibited a normal second positive phototropism. These findings provide the first indication that low-fluence blue light induces phosphorylation of Zmphot1 and that this induced phosphorylation is crucial for the first positive phototropism. [ABSTRACT FROM AUTHOR]

Abstract Background Direct-seeding cultivation by deep-seeding of seeds (drill seeding) is becoming popular due to the scarcity of land and labor. However, poor emergence and inadequate seedling establishment can lead to yield loss in direct-seeding cultivation by deep-sowing. In rice, mesocotyl and coleoptile are primarily responsible for seedling emergence from deeper levels of soil. Results Quantitative trait loci (QTLs) for mesocotyl and coleoptile length at 5-cm seeding depth were detected using 98 backcross inbred lines from a cross between Kasalath and Nipponbare. Three QTLs qMel-1, qMel-3, and qMel-6 for mesocotyl length were identified on chromosomes 1, 3, and 6, respectively, in two independent replicates. At two QTLs, qMel-1 and qMel-3, the Kasalath alleles increased mesocotyl length, whereas Nipponbare allele increased at qMel-6. The Nipponbare alleles at two QTLs (qCol-3 and qCol-5) increased the coleoptile length. Further, seeds of 54 chromosome segment substitution lines (CSSLs) from the cross between Kasalath and Nipponbare sown at 5 cm soil depth showed a significant positive correlation between seedling emergence and mesocotyl elongation (r > 0.6, P