Gazanchian Ali, Hajheidari Mohsen, Sima Nayer Khoshkholgh, Salekdeh Ghasem Hosseini
Agricultural Biotechnology Research Institute of Iran (ABRII), PO Box 31535-1897, Karaj, Iran.
J Exp Bot. 2007;58(2):291-300. doi: 10.1093/jxb/erl226. Epub 2007 Jan 8.
Tall wheatgrass (Elymus elongatum Host) is a drought-tolerant, cool-season forage grass native to Iran. A proteomic approach has been applied to identify mechanisms of drought responsiveness and tolerance in plants undergoing vegetative stage drought stress and then recovery after rewatering. Uniformed clones were reproduced from a parent plant collected from Brojen (central region of Iran). Clones were grown in pots and drought was initiated by withholding water for 16 d. The leaf samples were taken in triplicate from both stressed/rewatered plants and continuously watered controls at five times: (i) 75% FC, (ii) 50% FC, (iii) 25% FC, (iv) 3 d after rewatering, and (v) 14 d after rewatering. Changes in the proteome pattern of shoots were studied using two-dimensional gel electrophoresis. Following the 16 d water stress, both shoot dry weight and leaf width decreased up to 67% compared with the well-watered plants, whereas proline content increased up to 20-fold. Leaf relative water contents (RWC) also declined from 85% to 24%. Out of about 600 protein spots detected on any given two-dimensional gel, 58 protein spots were reproducibly and significantly changed during drought stress and recovery. Only one protein (abscisic acid- and stress-inducible protein) showed significant changes in expression and position in response to severe drought. The fifty-eight responsive proteins were categorized in six clusters including two groups of proteins specifically up- and down-regulated in response to severe drought stress. Eighteen proteins belonging to these two groups were analysed by liquid chromatography tandem mass spectrometry leading to the identification of 11 of them, including the oxygen-evolving enhancer protein 2, abscisic acid- and stress-inducible protein, several oxidative stress tolerance enzymes, two small heat shock proteins, and Rubisco breakdown. The results suggest that E. elongatum may tolerate severe drought stress by accumulating proline and several proteins related to drought-stress tolerance. Recovery after rewatering might be another mechanism by which plants tolerate erratic rainfall in semi-arid regions.
高冰草（Elymus elongatum Host）是一种原产于伊朗的耐旱冷季型饲草。采用蛋白质组学方法来确定处于营养生长阶段干旱胁迫及复水后恢复过程的植物中干旱响应和耐受机制。从采集自伊朗中部地区布罗詹的一株母本植物繁殖出一致的克隆植株。将克隆植株种植于花盆中，通过停水16天引发干旱。从受胁迫/复水植株和持续浇水的对照植株中各取三份叶片样本，共取五次：（i）田间持水量的75%时，（ii）田间持水量的50%时，（iii）田间持水量的25%时，（iv）复水后3天，以及（v）复水后14天。使用二维凝胶电泳研究地上部蛋白质组模式的变化。在16天水分胁迫后，与充分浇水的植株相比，地上部干重和叶宽均下降高达67%，而脯氨酸含量增加高达20倍。叶片相对含水量（RWC）也从85%降至24%。在任何给定的二维凝胶上检测到的约600个蛋白质点中，有58个蛋白质点在干旱胁迫和恢复过程中可重复且显著变化。仅一种蛋白质（脱落酸和胁迫诱导蛋白）在响应严重干旱时表达和位置有显著变化。这58种响应蛋白被分为六个簇，包括两组分别在响应严重干旱胁迫时特异性上调和下调的蛋白质。对属于这两组的18种蛋白质进行了液相色谱串联质谱分析，鉴定出其中11种，包括放氧增强蛋白2、脱落酸和胁迫诱导蛋白、几种氧化应激耐受酶、两种小分子热激蛋白以及核酮糖-1,5-二磷酸羧化酶/加氧酶降解产物。结果表明，高冰草可能通过积累脯氨酸和几种与干旱胁迫耐受相关的蛋白质来耐受严重干旱胁迫。复水后的恢复可能是植物耐受半干旱地区降雨无常的另一种机制。
