玉米幼苗根不同区段中ZmPIPs对短期水分胁迫及复水的转录响应

Transcription Regulation of ZmPIPs in Different Young Maize Root Zones Responses to Short Term Water Stress and Rewater

通过10%PEG-6000短期处理水培7～8 d的玉米(Zea mays L.)幼苗以及水分胁迫处理48 h后短期复水两个过程,用实时荧光定量PCR技术检测了水分胁迫及复水处理数小时后成熟根段和幼嫩根段中4种主要玉米质膜水通道蛋白(ZmPIPs)的mRNA相对含量变化,以研究环境水分条件变化对水通道蛋白表达的影响及其调节机制。结果显示:正常水分条件与胁迫48 h后根成熟区和幼根区段的4种ZmPIPs的mRNA含量变化均表现出明显的昼夜周期规律,成熟根段中ZmPIPs的mRNA相对含量峰值出现在白天中午,而幼嫩根段中则在中午左右最低。水分胁迫后数小时内根中ZmPIP2;5明显下调而其他ZmPIPs变化不大;复水后幼根区段4种ZmPIPs的mRNA相对含量均大幅上调,而根成熟区的ZmPIP1;2和ZmPIP2;5却下调。研究发现,玉米植株对环境水分条件适应后,根成熟区段和幼嫩区段中4种PIPs转录调节的昼夜日变化规律相反;短期水分胁迫及复水时其根不同区段中ZmPIPs也进行着差异性转录调节;推测玉米根不同区段的结构和功能差异可能是这些差异的形成原因之一。

Roles of aquaporins in plant water relations under changeable water conditions are known little.Our objective was to investigate transcriptional regulation of aquaporins in different root tissues under water stress and the later rewatering.Maize seeds（line：478） were chosen,germinated and grown in a humid atmosphere with 1/2 Hoagland solution.After 7～8 d,10% PEG-6000 was used to form water stress and 48 h later plants were rewatered.Root samples was harvested every two hours after treatments and the relative amounts of mRNA encoding four Zea mays plasma membrane AQPs（ZmPIPs） were determined by Q-RT-PCR.In well water and water stress maintained 48 h conditions,transcription of four ZmPIPs was exactly regulated and clearly shown a diurnal rhythm both in root mature zones and elongation zones.Furthermore,in root mature zones,transcription of ZmPIPs was up regulated after dawn and came to their maximums at 10：00 or 12：00,but in cell elongation zones it was down regulated when lighted and up regulated before evening.After water stress by 10%PEG,ZmPIP2;5 was down regulated in roots significantly,but other three ZmPIPs didn＇t change so much compared with their controls.When plants were rewatered,transcription of ZmPIPs was greatly up regulated in root elongation zones,meanwhile,ZmPIP1;1 and ZmPIP2;2 were also up regulated while ZmPIP1;2 and ZmPIP2;5 were down regulated in root mature zones.This may suggest that when face to changeable sounding water conditions,plants can regulate transcription of PIPs in roots differently and accurately,according to tissues＇ structures and functions,to get a compromise with the new water condition.