Conversion of endogenous indole-3-butyric acid to indole-3-acetic acid drives cell expansion in Arabidopsis seedlings.
Conversion of endogenous indole-3-butyric acid to indole-3-acetic acid drives cell expansion in Arabidopsis seedlings.
复制标题
DOI：
10.1104/pp.110.157461
复制
发表时间：
2010-08-01
期刊：
影响因子：
7.4
通讯作者：
Bartel, Bonnie
中科院分区：
文献类型：
--
作者：
Strader, Lucia C;Culler, Angela Hendrickson;Bartel, Bonnie
拟南芥的遗传证据表明，生长素前体吲哚-3-丁酸(IBA)通过过氧化体β-氧化作用转化为活性吲哚-3-乙酸(IAA)；然而，目前还缺乏直接证据表明拟南芥将IBA转化为IAA，而且IBA衍生的IAA的作用也不是很清楚。在这项工作中，我们直接证明了拟南芥幼苗将IBA转化为IAA。此外，我们还发现几个IBA抗性、IAA敏感的突变体在IBA到IAA的转化过程中存在缺陷，包括吲哚-3-丁酸应答1(Ibr1)ibr3 ibr10三重突变体，它在三种可能直接参与过氧化体IBAβ氧化的酶中存在缺陷。除了IBA到IAA的转化缺陷外，ibr1、ibr3、ibr10三重突变体的根毛比野生型更短，子叶更小；这些细胞扩张缺陷表明某些组织中IAA水平较低。与这种可能性一致，我们可以用外源生长素挽救ibr1、ibr3、ibr10短根毛表型。IAA-氨基酸偶联物是IAA的第二类前体，三重突变体表现为下胚轴伸长减小，但子叶大小正常，根毛长度略有缩短。我们的数据表明，IBA的β-氧化和IAA-氨基酸共轭水解为部分不同的发育过程提供了生长素，IBA衍生的IAA在幼苗发育过程中推动根毛和子叶细胞扩张方面发挥了主要作用。
Genetic evidence in Arabidopsis (Arabidopsis thaliana) suggests that the auxin precursor indole-3-butyric acid (IBA) is converted into active indole-3-acetic acid (IAA) by peroxisomal beta-oxidation; however, direct evidence that Arabidopsis converts IBA to IAA is lacking, and the role of IBA-derived IAA is not well understood. In this work, we directly demonstrated that Arabidopsis seedlings convert IBA to IAA. Moreover, we found that several IBA-resistant, IAA-sensitive mutants were deficient in IBA-to-IAA conversion, including the indole-3-butyric acid response1 (ibr1) ibr3 ibr10 triple mutant, which is defective in three enzymes likely to be directly involved in peroxisomal IBA beta-oxidation. In addition to IBA-to-IAA conversion defects, the ibr1 ibr3 ibr10 triple mutant displayed shorter root hairs and smaller cotyledons than wild type; these cell expansion defects are suggestive of low IAA levels in certain tissues. Consistent with this possibility, we could rescue the ibr1 ibr3 ibr10 short-root-hair phenotype with exogenous auxin. A triple mutant defective in hydrolysis of IAA-amino acid conjugates, a second class of IAA precursor, displayed reduced hypocotyl elongation but normal cotyledon size and only slightly reduced root hair lengths. Our data suggest that IBA beta-oxidation and IAA-amino acid conjugate hydrolysis provide auxin for partially distinct developmental processes and that IBA-derived IAA plays a major role in driving root hair and cotyledon cell expansion during seedling development.