Leibniz-Institute of Plant Genetics and Crop Plant Research (IPK), Correnstrasse 03, D-06466 Gatersleben, Germany.
J Exp Bot. 2011 May;62(8):2615-32. doi: 10.1093/jxb/erq446. Epub 2011 Feb 2.
Drought is one of the most severe environmental stress factors limiting crop yield especially when occurring during anthesis and seed filling. This terminal drought is characterized by an excess production of the phytohormone abscisic acid (ABA) which plays an important role during seed development and dormancy. All the genes putatively involved in ABA biosynthesis and inactivation in barley were identified and their expression studied during plant ontogeny under standard and drought-stress conditions to learn more about ABA homeostasis and the possible mode of cross-talk between source and sink tissues. Out of 41 genes related to ABA biosynthesis and inactivation 19 were found to be differentially regulated under drought stress in both flag leaves and developing seed during seed filling. Transcripts of plastid-located enzymes are regulated similarly in flag leaf and seed under terminal drought whereas transcripts of cytosolic enzymes are differentially regulated in the two tissues. Detailed information on the expression of defined gene family members is supplemented by measurements of ABA and its degradation and conjugation products, respectively. Under drought stress, flag leaves in particular contain high concentrations of both ABA and the ABA degradation products phaseic acid (PA) and diphaseic acid (DPA); whereas, in seeds, besides ABA, DPA was mainly found. The measurements also revealed a positive correlation between ABA level and starch content in developing seeds for the following reasons: (i) genes of the ABA controlled SnRK2.6 and RCAR/PP2C-mediated signal transduction pathway to the ABF transcription factor HvABI5 are activated in the developing grain under drought, (ii) novel ABA- and dehydration-responsive cis-elements have been found in the promoters of key genes of starch biosynthesis (HvSUS1, HvAGP-L1) and degradation (HvBAM1) and these transcripts/activity are prominently induced in developing seeds during 12 and 16 DAF, (iii) spraying of fluridone (an ABA biosynthesis inhibitor) to drought-stressed plants results in severely impaired starch content and thousand grain weight of mature seeds.
干旱是限制作物产量的最严重环境胁迫因素之一，尤其是在开花和种子灌浆期发生时。这种终末期干旱的特点是过量产生植物激素脱落酸（ABA），ABA 在种子发育和休眠过程中发挥重要作用。鉴定了拟在大麦中参与 ABA 生物合成和失活的所有基因，并在标准和干旱胁迫条件下研究了它们在植物个体发育过程中的表达情况，以更多地了解 ABA 动态平衡以及源和汇组织之间可能的串扰模式。在与 ABA 生物合成和失活相关的 41 个基因中，有 19 个在旗叶和灌浆期种子发育过程中在干旱胁迫下差异调节。质体定位酶的转录物在终末期干旱下在旗叶和种子中受到类似的调节，而胞质酶的转录物在两种组织中差异调节。定义基因家族成员表达的详细信息分别由 ABA 及其降解和共轭产物的测量来补充。在干旱胁迫下，特别是旗叶中含有高浓度的 ABA 和 ABA 降解产物（PA）和二氢 PA（DPA）；而在种子中，除了 ABA 外，主要发现 DPA。这些测量还揭示了发育种子中 ABA 水平与淀粉含量之间存在正相关，原因如下：（i）ABA 控制的 SnRK2.6 和 RCAR/PP2C 介导的信号转导途径的基因到 ABF 转录因子 HvABI5 在干旱下发育中的谷物中被激活，（ii）在淀粉生物合成（HvSUS1、HvAGP-L1）和降解（HvBAM1）的关键基因启动子中发现了新的 ABA 和脱水反应顺式元件，并且这些转录物/活性在发育中的种子中在 12 和 16 DAF 期间显著诱导，（iii）向干旱胁迫植物喷洒 fluridone（ABA 生物合成抑制剂）会严重损害成熟种子的淀粉含量和千粒重。
