Abstract

Optimizing plant architecture is an efficient approach for breeders to increase crop yields, and phytohormones such as gibberellins (GAs) play an important role in controlling growth. Medicago truncatula is a model legume species, but the molecular mechanisms underlying its architecture are largely unknown. In this study, we examined a tobacco retrotransposon Tnt1-tagged mutant collection of M. truncatula and identified dwarf and increased branching 1 (dib1), which exhibited extreme dwarfism and increased numbers of lateral branches. By analysis of the flanking sequences of Tnt1 insertions in different alleles of the tagged lines, we were able to clone DIB1. Linkage analysis and reverse screening of the flanking-sequence tags identified Medtr2g102570 as the gene corresponding to the DIB1 locus in the dib1 loss-of-function mutants. Phylogenetic analysis indicated that DIB1 was the ortholog of PsGA3ox1/Le in Pisum sativum. Expression analysis using a GUS-staining reporter line showed that DIB1 was expressed in the root apex, pods, and immature seeds. Endogenous GA₄ concentrations were markedly decreased whilst some of representative GA biosynthetic enzymes were up-regulated in the dib1 mutant. In addition, exogenous application of GA₃ rescued the dib1 mutant phenotypes. Overall, our results suggest that DIB1 controls plant height and axillary bud outgrowth via an influence on the biosynthesis of bioactive GAs. DIB1 could therefore be a good candidate gene for breeders to optimize plant architecture for crop improvement.

中文翻译：

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矮化和增加的分枝 1 控制蒺藜苜蓿的株高和腋芽生长。

摘要

优化植物结构是育种者提高作物产量的有效方法，而赤霉素 (GA) 等植物激素在控制生长方面发挥着重要作用。Medicago truncatula是一种模式豆科植物，但其结构背后的分子机制在很大程度上是未知的。在这项研究中，我们检查了烟草反转录转座子Tnt1标记的M. truncatula突变体集合，并确定了矮化和增加的分枝 1 ( dib1 )，其表现出极端的侏儒症和增加的侧枝数量。通过分析标记系的不同等位基因中Tnt1插入的侧翼序列，我们能够克隆DIB1。侧翼序列标签的连锁分析和反向筛选将 Medtr2g102570 鉴定为与dib1功能丧失突变体中的DIB1基因座相对应的基因。系统发育分析表明DIB1是豌豆PsGA3ox1/Le的直系同源物。使用 GUS 染色报告基因的表达分析表明DIB1在根尖、豆荚和未成熟种子中表达。内源性 GA ₄浓度显着降低，而一些代表性 GA 生物合成酶在dib1突变体中上调。此外，GA _{3的外源应用}拯救了dib1突变体表型。总体而言，我们的研究结果表明，DIB1通过影响生物活性 GA 的生物合成来控制植物高度和腋芽生长。因此， DIB1可能是育种者优化​​植物结构以改善作物的良好候选基因。