State Key Laboratory of Crop Biology, College of Life Science, Shandong Agricultural University, Tai'an 271018, Shandong, People's Republic of China.
Plant Cell Rep. 2012 Apr;31(4):671-85. doi: 10.1007/s00299-011-1185-9. Epub 2011 Nov 11.
Expansin protein is a component of the cell wall generally accepted to be the key regulator of cell wall extension during plant growth. Plant hormones regulate expansin gene expression as well as plant growth during drought stress. However, the relationship between expansin and plant hormone is far from clear. Here, we studied the involvement of expansin in plant cell growth mediated by the hormones indole-3-acetic acid (IAA) and abscisic acid (ABA) under osmotic stress which was induced by polyethylene glycol (PEG)-6000. Wheat coleoptiles from a drought-resistant cultivar HF9703 and a drought-sensitive cultivar 921842 were used to evaluate cell growth and expansin activity. Osmotic stress induced the accumulation of ABA. ABA induced expansin activity mainly by enhancing expansin expression, since ABA induced cell wall basification via decreasing plasma membrane H(+)-ATPase activity, which was unfavorable for expansin activity. Although ABA induced expansin activity and cell wall extension, treatment with exogenous ABA and/or fluridone (FLU, an ABA inhibitor) suggested that ABA was involved in the coleoptile growth inhibition during osmotic stress. IAA application to detached coleoptiles also enhanced coleoptile growth and increased expansin activity, but unlike ABA, IAA-induced expansin activity was mainly due to the decrease of cell wall pH by increasing plasma membrane H(+)-ATPase activity. Compared with drought-sensitive cultivar, the drought-resistant cultivar could maintain greater expansin activity and cell wall extension, which was contributive to its resultant faster growth under water stress.
扩展蛋白是细胞壁的一个组成部分，被普遍认为是植物生长过程中细胞壁延伸的关键调节因子。植物激素调节扩展素基因的表达以及干旱胁迫下植物的生长。然而，扩展素与植物激素之间的关系还远未清楚。在这里，我们研究了在渗透胁迫下（由聚乙二醇（PEG）-6000 诱导），激素吲哚乙酸（IAA）和脱落酸（ABA）介导的植物细胞生长中扩展素的参与情况。使用抗旱品种 HF9703 和抗旱敏感品种 921842 的小麦胚芽鞘来评估细胞生长和扩展素活性。渗透胁迫诱导 ABA 的积累。ABA 主要通过增强扩展素表达来诱导扩展素活性，因为 ABA 通过降低质膜 H(+)-ATPase 活性诱导细胞壁碱化，这不利于扩展素活性。尽管 ABA 诱导扩展素活性和细胞壁延伸，但用外源 ABA 和/或氟啶酮（FLU，ABA 抑制剂）处理表明 ABA 参与了渗透胁迫期间胚芽鞘生长的抑制。将外源 IAA 应用于离体胚芽鞘也增强了胚芽鞘的生长并增加了扩展素活性，但与 ABA 不同，IAA 诱导的扩展素活性主要是由于通过增加质膜 H(+)-ATPase 活性降低细胞壁 pH 值。与抗旱敏感品种相比，抗旱品种能够保持更高的扩展素活性和细胞壁延伸性，这有助于其在水分胁迫下更快的生长。
