Effect of Exogenous Abscisic Acid on psbA Expression at Grain Filling Stage in Two Wheat Cultivars Under Drought Stress

Abscisic acid (ABA) is an important plant hormone and may be involved in drought resistance in crops. The object of this study was to understand the effects of exogenous ABA on wheat (Triticum aestivum L.) plant under drought stress. After drought stress simulated with polyethylene glycol (PEG) for 72 h at grain-filling stage, flag leaves of Yumai 949 and Shaanmai 5 showed significant increase in malondialdehyde (MDA) content and decreases in relative water content (RWC), chlorophyll content, and yield. Meanwhile, the transcription of psbA gene in photosystem II system was also depressed according to the analysis of reverse transcriptional PCR. Application of exogenous ABA had a significant effect on alleviation of these reactions from PEG stress. Compared to Yumai 949, Shaanmai 5 received smaller injury in plasma membranes and less reduces in RWC, chlorophyll content, yield, and psbA transcriptional level after PEG stress. Moreover, exogenous ABA treatment resulted in restoration of all parameters tested to the levels before stress in Shaanmai 5. This result indicated that the expression of psbA gene was closely related to drought stress resistance subject to wheat cultivar. The primary evidence of ABA regulation on psbA expression may enrich the mechanism of drought resistance and suggest the potential of exogenous ABA to enhance resistance to drought stress in wheat during grain filling period.

摘 要以灌浆期的豫麦949和陕麦5号小麦品种为试材, PEG干旱处理72 h后, 比较了脱落酸(ABA)对小麦相对水分含量、叶绿素、丙二醛含量以及产量的影响, 并采用反转录半定量PCR方法测定PSII中psbA基因转录水平的变化。结果表明, 干旱胁迫明显降低小麦叶片中相对水分和叶绿素含量, 增加丙二醛含量, 抑制psbA基因的转录, 降低小麦的产量, 而外源ABA能明显缓解这些胁迫反应。与豫麦949相比, 陕麦5号中质膜损伤较小, 相对水分和叶绿素含量、产量以及psbA基因转录水平的下降也较小, 外源ABA处理后, 各参数也能够恢复到对照水平, 说明不同小麦品种的抗干旱胁迫能力与psbA基因的表达水平密切相关。本研究首次发现外源ABA能够调控干旱胁迫下灌浆期小麦psbA基因的表达, 稳定PSII系统中重要基因的转录水平, 从而提高灌浆期小麦的抗干旱胁迫能力。