Song Hongmiao, Zhao Rongmin, Fan Pengxiang, Wang Xuchu, Chen Xianyang, Li Yinxin
Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, 100093, Beijing, China.
Planta. 2009 Mar;229(4):955-64. doi: 10.1007/s00425-008-0886-y. Epub 2009 Jan 16.
Three AtHsp90 isoforms, cytosolic AtHsp90.2, chloroplast-located AtHsp90.5, and endoplasmic reticulum (ER)-located AtHsp90.7, were characterized by constitutive overexpressing their genes in Arabidopsis thaliana. Both types of the transgenic plants overexpressing cytosolic and organellar AtHsp90s showed reduced tolerance to salt and drought stresses with lower germination rates and fresh weights, but improved tolerance to high concentration of Ca(2+) comparing with the wild type plants. Transcriptional analysis of ABA-responsive genes, RD29A, RD22 and KIN2 under salt and drought stresses, indicated that the induction expression of these genes was delayed by constitutive overexpression of cytosolic AtHsp90.2, but was hardly affected by that of organellar AtHsp90.5 and AtHsp90.7. These results implied that Arabidopsis different cellular compartments-located Hsp90s in Arabidopsis might be involved in abiotic stresses by different functional mechanisms, probably through ABA-dependent or Ca(2+) pathways, and proper homeostasis of Hsp90 was critical for cellular stress response and/or tolerance in plants.
通过在拟南芥中组成型过表达其基因，对三种拟南芥热休克蛋白90（AtHsp90）亚型进行了表征，即胞质AtHsp90.2、定位于叶绿体的AtHsp90.5和定位于内质网（ER）的AtHsp90.7。与野生型植物相比，过表达胞质和细胞器AtHsp90s的两种转基因植物对盐和干旱胁迫的耐受性均降低，发芽率和鲜重较低，但对高浓度Ca(2+)的耐受性有所提高。对盐和干旱胁迫下ABA响应基因RD29A、RD22和KIN2的转录分析表明，胞质AtHsp90.2的组成型过表达延迟了这些基因的诱导表达，但细胞器AtHsp90.5和AtHsp90.7的过表达对其影响不大。这些结果表明，拟南芥中定位于不同细胞区室的Hsp90s可能通过不同的功能机制参与非生物胁迫，可能是通过ABA依赖或Ca(2+)途径，并且Hsp90的适当稳态对于植物的细胞应激反应和/或耐受性至关重要。
