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植物耐高温逆向调控机制查明
发布日期:2012/6/1 11:34:28 浏览次数:3108
植物耐高温逆向调控机制查明

郭房庆(来源:中科院上海生命科学研究院植物生理生态所)
中科院上海生命科学研究院植物生理生态所的科研人员日前揭示了高等植物叶绿体是细胞启动胞内热激反应的信号源,首次建立了叶绿体蛋白翻译效率和细胞核热胁迫响应转录因子HsfA2表达启动的遗传关系,证实了植物细胞存在热激反应的叶绿体逆向调控信号途径。相关成果近日在线发表于《公共科学图书馆—遗传学》。
据介绍,植物在高温胁迫下会产生应激防御反应,启动体内大量热激转录因子(HSF)和热激蛋白(HSP)基因的转录,从而维护细胞和叶绿体的稳定性,但对于启动这些热激响应基因表达的信号来源并不清楚。
为回答植物在高温胁迫下如何维持叶绿体稳定性这一问题,研究员郭房庆指导博士生于海东等开展了植物高温胁迫响应蛋白的鉴定工作。研究表明,叶绿体核糖体蛋白RPS1参与类囊体膜蛋白的翻译,并且RPS1的表达水平以剂量依赖的方式调控类囊体膜结构的稳定性。尤为重要的是,RPS1表达水平下调导致拟南芥突变体对高温胁迫极度敏感,其原因是RPS1突变体在高温胁迫条件下热激转录因子HsfA2及其下游靶基因的表达受到严重抑制。同时,组成型表达HsfA2可将RPS1类囊体膜稳定性和耐热性恢复至野生型水平。
该课题组就此提出了植物细胞热激反应逆向调控机制模型:RPS1作为叶绿体蛋白翻译调控的关键因子,其蛋白表达水平受高温胁迫的诱导;RPS1表达增强可提高类囊体膜蛋白的翻译效率,对于维持高温胁迫下叶绿体的功能状态和产生质体逆向信号是必要的。产生的质体信号通过相关的热激信号转导组分传递到细胞核,从而启动HsfA2和其下游靶基因的热激响应表达。而HsfA2下游靶基因编码的叶绿体定位的热激蛋白如HSP21等进入叶绿体,对高温胁迫下的叶绿体类囊体膜系统进行保护。
专家认为,该研究为细胞核—质体信号互作参与植物逆境胁迫适应机制提供了新证据,为进一步研究植物的耐热性状形成机理开启了新视角。同时,该发现为通过调控质体翻译效率增强农作物的耐高温胁迫能力提供了全新的遗传改良操作路径。(来源:中国科学报 黄辛)
 

Downregulation of Chloroplast RPS1 Negatively Modulates Nuclear Heat-Responsive Expression of HsfA2 and Its Target Genes in Arabidopsis

SprMorn 添加于 2012-5-29 11:14:59 215次阅读 | 0次推荐 | 0个评论

Heat stress commonly leads to inhibition of photosynthesis in higher plants. The transcriptional induction of heat stress-responsive genes represents the first line of inducible defense against imbalances in cellular homeostasis. Although heat stress transcription factor HsfA2 and its downstream target genes are well studied, the regulatory mechanisms by which HsfA2 is activated in response to heat stress remain elusive. Here, we show that chloroplast ribosomal protein S1 (RPS1) is a heat-responsive protein and functions in protein biosynthesis in chloroplast. Knockdown of RPS1 expression in the rps1 mutant nearly eliminates the heat stress-activated expression of HsfA2 and its target genes, leading to a considerable loss of heat tolerance. We further confirm the relationship existed between the downregulation of RPS1 expression and the loss of heat tolerance by generating RNA interference-transgenic lines of RPS1. Consistent with the notion that the inhibited activation of HsfA2 in response to heat stress in the rps1 mutant causes heat-susceptibility, we further demonstrate that overexpression of HsfA2 with a viral promoter leads to constitutive expressions of its target genes in the rps1 mutant, which is sufficient to reestablish lost heat tolerance and recovers heat-susceptible thylakoid stability to wild-type levels. Our findings reveal a heat-responsive retrograde pathway in which chloroplast translation capacity is a critical factor in heat-responsive activation of HsfA2 and its target genes required for cellular homeostasis under heat stress. Thus, RPS1 is an essential yet previously unknown determinant involved in retrograde activation of heat stress responses in higher plants.

作 者:Hai-Dong Yu, Xiao-Fei Yang, Si-Ting Chen, Yu-Ting Wang, Ji-Kai Li, Qi Shen, Xun-Liang Liu, Fang-Qing Guo*
期刊名称: plos genetics
期卷页: 第卷 第期 页
学科领域:生命科学 » 植物学 » 植物生理与生化
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原文链接:http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002669
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