Dataset Information

Mesocotyl Elongation is Essential for Seedling Emergence Under Deep-Seeding Condition in Rice.

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 < 0.0001), but not with coleoptile elongation (r = 0.05, P = 0.7). Seedling emergence of Nipponbare, Kasalath, and the 3 of the 54 CSSLs rapidly decreased with increasing sowing depth. Seedling emergence at seeding depths of 7 and 10 cm was faster in Kasalath and CSSL-5 that harbored the Kasalath alleles across the qMel-1 and qMel-3 regions than in the other two CSSLs that contained a single QTL and Nipponbare alleles. CSSL-5 showed the longest mesocotyl among the 3 CSSLs, but no difference in coleoptile length was observed among the 3 CSSLs at seeding depths of 7 and 10 cm. CONCLUSION:Variation of mesocotyl elongation was found to be associated with seedling emergence at the seeding depth of 5 cm. To our knowledge, this is the first study performed using CSSLs to detect QTLs for mesocotyl or coleoptile elongation and to determine the effect of mesocotyl elongation on seedling emergence in rice. Our findings provides a foundation for developing rice cultivars that show higher seedling emergence after direct seeding by introgressing QTLs for mesocotyl elongation in rice breeding.

SUBMITTER: Lee HS

PROVIDER: S-EPMC5511125 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Mesocotyl Elongation is Essential for Seedling Emergence Under Deep-Seeding Condition in Rice.

Lee Hyun-Sook HS Sasaki Kazuhiro K Kang Ju-Won JW Sato Tadashi T Song Won-Yong WY Ahn Sang-Nag SN

Rice (New York, N.Y.) 20170714 1

<h4>Background</h4>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.<h4>Results</h4>Quantitative trait loci (QTLs) for mesocotyl and coleoptile length at 5-cm seeding depth were det ...[more]

PMID: 28710696

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Project description:Mesocotyl elongation is a key trait influencing seedling emergence and establishment in direct-seeding rice cultivation. The phytohormone gibberellin (GA) has positive effects on mesocotyl elongation in rice. However, the physiological and molecular basis underlying the regulation of mesocotyl elongation mediated by GA priming under deep-sowing conditions remains largely unclear. In the present study, we performed a physiological and comprehensive transcriptomic analysis of the function of GA priming in mesocotyl elongation and seedling emergence using a direct-seeding japonica rice cultivar ZH10 at a 5-cm sowing depth. Physiological experiments indicated that GA priming significantly improved rice seedling emergence by increasing the activity of starch-metabolizing enzymes and compatible solute content to supply the energy essential for subsequent development. Transcriptomic analysis revealed 7074 differentially expressed genes (false discovery rate of <0.05, |log2(fold change)| of ≥1) after GA priming. Furthermore, gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses revealed that genes associated with transcriptional regulation, plant hormone biosynthesis or signaling, and starch and sucrose metabolism were critical for GA-mediated promotion of rice mesocotyl elongation. Further analyses showed that the expression of the transcription factor (TF) genes (v-myb avian myeloblastosis viral oncogene homolog (MYB) alternative splicing 1 (MYBAS1), phytochrome-interacting factors 1 (PIF1), Oryza sativa teosinte branched 1/cycloidea/proliferating cell factor 5 (OsTCP5), slender 1 (SLN1), and mini zinc finger 1 (MIF1)), plant hormone biosynthesis or signaling genes (brassinazole-resistant 1 (BZR1), ent-kaurenoic acid oxidase-like (KAO), GRETCHEN HAGEN 3.2 (GH3.2), and small auxin up RNA 36 (SAUR36)), and starch and sucrose metabolism genes (α-amylases (AMY2A and AMY1.4)) was highly correlated with the mesocotyl elongation and deep-sowing tolerance response. These results enhance our understanding of how nutrient metabolism-related substances and genes regulate rice mesocotyl elongation. This may facilitate future studies on related genes and the development of novel rice varieties tolerant to deep sowing.

Project description:Serotonin (5-HT), an indoleamine compound, has been known to mediate many physiological responses of plants under environmental stress. The deep-seeding (≥20 cm) of maize seeds is an important cultivation strategy to ensure seedling emergence and survival under drought stress. However, the role of 5-HT in maize deep-seeding tolerance remains unexplored. Understanding the mechanisms and evaluating the optimal concentration of 5-HT in alleviating deep-seeding stress could benefit maize production. In this study, two maize inbred lines were treated with or without 5-HT at both sowing depths of 20 cm and 3 cm, respectively. The effects of different concentrations of 5-HT on the growth phenotypes, physiological metabolism, and gene expression of two maize inbred lines were examined at the sowing depths of 20 cm and 3 cm. Compared to the normal seedling depth of 3 cm, the elongation of the mesocotyl (average elongation 3.70 cm) and coleoptile (average elongation 0.58 cm), secretion of indole-3-acetic acid (IAA; average increased 3.73 and 0.63 ng g-1 FW), and hydrogen peroxide (H2O2; average increased 1.95 and 0.63 μM g-1 FW) in the mesocotyl and coleoptile were increased under 20 cm stress, with a concomitant decrease in lignin synthesis (average decreased 0.48 and 0.53 A280 g-1). Under 20 cm deep-seeding stress, the addition of 5-HT activated the expression of multiple genes of IAA biosynthesis and signal transduction, including Zm00001d049601, Zm00001d039346, Zm00001d026530, and Zm00001d049659, and it also stimulated IAA production in both the mesocotyl and coleoptile of maize seedlings. On the contrary, 5-HT suppressed the expression of genes for lignin biosynthesis (Zm00001d016471, Zm00001d005998, Zm00001d032152, and Zm00001d053554) and retarded the accumulation of H2O2 and lignin, resulting in the elongation of the mesocotyl and coleoptile of maize seedlings. A comprehensive evaluation analysis showed that the optimum concentration of 5-HT in relieving deep-seeding stress was 2.5 mg/L for both inbred lines, and 5-HT therefore could improve the seedling emergence rate and alleviate deep-seeding stress in maize seedlings. These findings could provide a novel strategy for improving maize deep-seeding tolerance, thus enhancing yield potential under drought and water stress.

Project description:BackgroundDue to the diversity of rice varieties and cropping systems in China, the limitation of seeding density and seedling quality makes it hard to improve machine-transplanted efficiency. Previous studies have shown that indica and japonica varieties varied in machine transplanting efficiency and optimal seeding density. In this study, a RIL population derived from '9311' and 'Nipponbare' were performed to explore the seedling traits variations and the genetic mechanism under three seeding densities.ResultsThe parents and RIL population exhibited similar trends as the seeding density increased, including seedling height and first leaf sheath length increases, shoot dry weight and root dry weight decreases. Among the 37 QTLs for six traits detected under the three seeding densities, 12 QTLs were detected in both three seeding densities. Five QTL hotspots identified clustered within genomic regions on chromosomes 1, 2, 4, 6 and 11. Specific QTLs such as qRDW1.1 and qFLSL5.1 were detected under low and high seeding densities, respectively. Detailed analysis the QTL regions identified under specific seeding densities revealed several candidate genes involved in phytohormones signals and abiotic stress responses. Whole-genome additive effects showed that '9311' contributed more loci enhancing trait performances than 'Nipponbare', indicating '9311' was more sensitive to the seeding density than 'Nipponbare'. The prevalence of negative epistasis effects indicated that the complementary two-locus homozygotes may not have marginal advantages over the means of the two parental genotypes.ConclusionsOur results revealed the differences between indica rice and japonica rice seedling traits in response to seeding density. Several QTL hotspots involved in different traits and specific QTLs (such as qRDW1.1 and qFLSL5.1) in diverse seeding densities had been detected. Genome-wide additive and two-locus epistasis suggested a dynamic of the genetic control underlying different seeding densities. It was concluded that novel QTLs, additive and epistasis effects under specific seeding density would provide adequate information for rice seedling improvement during machine transplanting.

Dataset Information

Mesocotyl Elongation is Essential for Seedling Emergence Under Deep-Seeding Condition in Rice.

Publications

Mesocotyl Elongation is Essential for Seedling Emergence Under Deep-Seeding Condition in Rice.

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