光系统II亚基蛋白Q(Photosystem II subunit Q, PsbQ)是组成光系统II(PSII)复合体的重要外周蛋白之一,对维持PSII放氧活力起重要作用。在盐胁迫下,高浓度的Na+和Cl-在叶绿体中积累会严重破坏叶绿体的结构,抑制光合作用,使植物生长缓慢。文章通过筛选盐生植物四翅滨藜(Atriplex canescens) cDNA文库,获得一个在PSII中与放氧关系密切的放氧复合体蛋白基因PsbQ,命名为AcPsbQ1(GenBank登录号：KJ027025)。AcPsbQ1基因开放阅读框为699 bp,编码由233个氨基酸组成的前体蛋白。为了研究该基因的功能,文章克隆了AcPsbQ1基因并转化至酵母中,高盐和干旱胁迫处理实验表明转AcPsbQ1基因酵母相比于野生型酵母对高盐和干旱有更强的耐受力。为了进一步研究AcPsbQ1是否参与植物抗逆应答反应,利用实时荧光定量PCR法测定AcPsbQ1在胁迫处理条件下的表达变化。结果表明,用0.4 mol/L NaCl处理四翅滨藜12 h后,AcPsbQ1基因的表达量明显高于未处理的对照,表明AcPsbQ1基因的表达受盐胁迫诱导,同时,干旱胁迫也会提高AcPsbQ1基因的表达水平。上述结果表明该基因可能参与盐生植物四翅滨藜的抗逆胁迫应答反应。
PsbQ is an extrinsic subunit of the photosystem II in eukaryotic photosynthetic organisms. Numerous studies have demonstrated that PsbQ can stabilize the inorganic cofactors and enhance the oxygen release in PSII. The decrease of photosynthesis rate under salinity condition is normally attributed to the high concentration of injurious ions, such as Na+ and Cl-, which accumulate in the chloroplast and damage thylakoid membrane under salinity stress. In this study, AcPsbQ1 was isolated from a halophyte Atriplex canescens cDNA library. The AcPsbQ1 contains an open reading frame of 699 bp encoding a 233 amino acid protein. In order to investigate its function, AcPsbQ1 was cloned and transformed into Saccharomyces cerevisiae INVSc1. The heterologous expression of AcPsbQ1 in transgenic yeast significantly helped to increase the adapting and recovery ability of yeast cells under the salt and drought. Quantitative real-time PCR assay was performed to reveal the expression pattern of AcPsbQ1 under different abiotic stresses. On exposure to NaCl stress, the transcript level of AcPsbQ1 was significantly enhanced. AcPsbQ1 expression level was also up-regulated under drought stress. These results indicated that AcPsbQ1 might involve in the response to salt stress in A. canescens.
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