【摘要】 硫氧还蛋白(Trxs)能调控细胞的氧化还原状态,在木本植物中Trxs与耐盐性的关系尚未研究。本文克隆了非泌盐红树秋茄的硫氧还蛋白基因KcTrxf,并研究KcTrxf在植物耐盐性中的作用。qRT-PCR结果显示,秋茄在盐胁迫下KcTrxf表达量上调,并且叶片中的非蛋白巯基(NPTs)的含量上升。KcTrxf基因的开放阅读框(ORF)长585bp,编码194个氨基酸,是一类定位于叶绿体中的f类硫氧还蛋白。将重组的35S:KcTrxf表达载体转入模式植物烟草中进行耐盐性分析,结果表明,KcTrxf提高了烟草的耐盐性。NaCl处理下,野生型烟草叶片中膜质氧化,并且积累大量活性氧,使叶绿素含量以及叶绿素a/b比值明显下降。转基因烟草一方面通过提高过氧化氢酶(CAT)以及抗坏血酸过氧化物酶(APX)的活性来清除H2O2,另一方面通过调节抗坏血酸-谷胱甘肽循环中(AsA-GSH cycle)的关键酶单脱氧抗坏血酸还原酶(MDAR)以及谷胱甘肽还原酶(GR)的活性来增加还原型谷胱甘肽水平,同时,还增加了叶片中非蛋白巯基的含量,进而清除活性氧,减少盐害引起氧化胁迫。因此,盐胁迫下转基因烟草中的叶绿素含量以及叶绿素a/b维持较高水平,从而维持较高的光合速率和生长状态。更多还原

【Abstract】 Thioredoxins( Trxs) play a crucial role in mediating the redox state in living cells; however,little is known how Trxs mediate salt tolerance in woody species. The aim of this study was to clone putative Trxf from non-secretor mangrove Kandelia candel and analyze its role in Na Cl tolerance. Salt treatment enhanced NPTs( non-protein thiols) contents and increased transcription of Trxf in K. candel. The Kc Trxf gene contained an open reading frame of 585 bp encoding a putative thioredoxin protein with 194 amino acids. Sequence and localization analyses revealed that Kc Trxf is a typical thioredoxin in the chloroplast.To clarify the role of KcTrxf in salinity tolerance,it was transferred to tobacco,a model experimental system for functional genetics. Kc Trxf-transgenic lines were more salt tolerant than wild-type( WT)tobacco. In the WT tobacco,salinity( 100 mmol / L NaCl) resulted in a marked reduction of chlorophyll content,and chlorophyll a / b ratio. The salt damage in WT resulted presumably from lipid peroxidation and ROS accumulation. However,the salt treatment caused less damage in Kc Trxf-transgenic plants because of the up-regulated activity of catalase and ascorbate peroxidase. Moreover,KcTrxf-transgenicplants were able to increase the activities of MDAR( monodehydroascorbate reductase) and GR( glutathione reductase) in chloroplast AsA-GSH cycle,leading to an increase in the ratio of reduced glutathione( GSH) to oxidized glutathion( GSSG) and NPTs in the leaves. Therefore,KcTrxf-transgenic plants could better scavenge the salt-elicited reactive oxygen species( ROS) in leaf cells,compared to WT plants. In this way,reduction of chlorophyll content,and chlorophyll a / b ratio of Kc Trxf-transgenic plants was consequently less restricted. As a result,KcTrxf-transgenic plants maintain photosynthesis and growth under salinity in the longer term.更多还原