Centre for Applied Mathematics and Computational Science , Saha Institute of Nuclear Physics , 1/AF Bidhan Nagar , Kolkata- 700064 , India.
AoB Plants. 2010;2010:plq023. doi: 10.1093/aobpla/plq023. Epub 2010 Dec 30.
Plants can withstand many abiotic stresses. Stress adaptation through retention of imprints of previous stress exposure has also been described in plants. We have characterized the imprint or memory of adaptive stress responses of rice seedlings to arsenic (As) and heat stress.
Two-week-old rice seedlings (both with and without As) were given a 45 °C heat shock for 3 h. While under heat shock, the leafy portion of the seedlings was harvested at regular intervals. Subsequently, the seedlings were kept at room temperature for recovery and sampling continued over 3 h. Total RNA and protein were extracted from the leafy portion of the seedlings and complementary DNA (cDNA) was prepared from total RNA. The cDNA was used as a template for the polymerase chain reaction to identify the transcription level of HSP70. Protein extracted from the seedlings was western-blotted. HSP70 and actin (loading control) antibodies were used to recognize the proteins on the same blot.
Our studies reveal that HSP70, a cellular chaperone gene, is over-expressed at the mRNA and protein levels when rice seedlings are exposed to As and heat. The effect is cumulative and increases with the duration of stress for 3 h. During 3 h recovery from heat stress at ambient temperatures for 3 h, the chaperone remains expressed at higher levels in plants pre-exposed to As.
Our findings demonstrate a retention of the imprint of previous stress exposure, perhaps through sustained activation of the signalling pathways upstream of over-expression of HSP70. Furthermore, stress-induced HSP70 expression was additive/cumulative for continued exposure to similar or different kinds of stress, indicating that a commonality of signal transduction networks is adopted when plants experience more than one stress.
植物可以耐受许多非生物胁迫。植物中也描述了通过保留先前胁迫暴露的印迹来适应胁迫。我们已经描述了水稻幼苗对砷（As）和热胁迫的适应应激反应的印迹或记忆。
将两周大的水稻幼苗（有和没有 As）进行 45°C 的热冲击 3 小时。在热冲击过程中，每隔一段时间收获幼苗的叶状部分。随后，将幼苗保持在室温下恢复，并且在 3 小时内继续采样。从幼苗的叶状部分提取总 RNA 和蛋白质，并从总 RNA 制备 cDNA。使用 cDNA 作为模板进行聚合酶链反应，以鉴定 HSP70 的转录水平。从幼苗中提取蛋白质进行 Western 印迹。使用 HSP70 和肌动蛋白（加载对照）抗体来识别同一印迹上的蛋白质。
我们的研究表明，当水稻幼苗暴露于 As 和热时，细胞伴侣基因 HSP70 在 mRNA 和蛋白质水平上过度表达。这种影响是累积的，并随着应激持续 3 小时而增加。在 3 小时的室温下从热应激中恢复 3 小时期间，在预先暴露于 As 的植物中，伴侣蛋白仍然以更高的水平表达。
我们的发现表明，可能通过 HSP70 过表达的上游信号通路的持续激活，保留了先前应激暴露的印迹。此外，应激诱导的 HSP70 表达对于持续暴露于相似或不同种类的应激是累加的，这表明当植物经历多种应激时，信号转导网络的共性被采用。
