ECOTHERM – Exploring the natural variation of the heat shock response in Arabidopsis thaliana to understand the molecular mechanism of heat perception

暴露在适度升高的温度下会引发基因编码的热休克反应（HSR），导致短期获得性热耐受性，这使植物能够承受随后的极端温度，这对未适应的植物来说是致命的。HSR的特点是大量的转录和代谢重编程，由复杂的转录因子网络严格调节。这个调控网络的核心是属于A1亚家族（HSFA1s）的热休克转录因子的激活。尽管在拟南芥中，HSR已经在分子水平上得到了很好的表征，但植物如何感知温度的升高以及这个初始信号如何转化为HSFA1的激活，仍然不清楚。此外，对拟南芥温度响应的自然变化及其机制的认识有限。在我们的初步工作中，我们观察到十个拟南芥材料获得耐热性的能力有显著差异。此外，植物的存活与棉子糖的积累相关，棉子糖是一种三糖，其温度依赖性的合成受到HSFA1的正调控，使其成为HSR发病的一个有希望的标记性状。基于这些观察结果，我们建议利用温度依赖性棉子糖积累来：(1)深入了解HSFA1依赖性信号传导的遗传结构及其种内变异的机制；(2)在全基因组关联研究（GWAS）中确定参与温度感知的候选基因以及HSFA1信号传导级联的未知成分。我们将采用两步方法，首先对100份拟南拟南植物材料进行hsr相关标记性状的初步表征，这将导致极端材料的鉴定，并允许在第二步对大规模表型的实验条件进行微调。鉴定的极端加入将在代谢和转录组学水平上使用脂质组学和RNAseq进行详细表征。选择的差异表达基因的转录率将在100个条目中进行分析，并将数据用于生成转录网络，从而确定观察到的种内变异背后的中心调控元件。第二步，我们将筛选最近发表的1135份拟南芥的温度响应性，从而为GWA研究提供良好的资源。最重要的候选基因将被表征，并确定它们在温度感知和获得性耐热性中的确切作用。综上所述，该项目将为温度传感的分子机制以及局部适应极端温度的机制提供有价值的见解。

Exposure to moderately elevated temperatures elicits a genetically encoded heat shock response (HSR) resulting in short-term acquired thermotolerance, which enables plants to withstand a subsequent temperature extreme that is lethal to non-acclimated plants. The HSR is characterised by a substantial transcriptional and metabolic reprogramming that is tightly regulated by a complex network of transcription factors. Central to this regulatory network is the activation of HEAT SHOCK TRANSCRIPTION FACTORs belonging to the A1 subfamily (HSFA1s). Despite the fact that the HSR has been relatively well characterised at the molecular level in Arabidopsis thaliana it is still unclear how an increase in temperature is sensed by the plant and how this initial signal translates into HSFA1 activation. In addition, knowledge on the natural variation of A. thaliana’s temperature responsiveness and the underlying mechanisms is limited. In our preliminary work we observed a significant variation in the ability to acquire thermotolerance across ten Arabidopsis accessions. In addition, plant survival correlated with the accumulation of raffinose, a trisaccharide whose temperature-dependent synthesis is positively regulated by HSFA1, making it a promising marker trait for the onset of the HSR. Based on these observations we propose to exploit the temperature-dependent raffinose accumulation to (I) gain insights into the genetic architecture of HSFA1-dependent signalling and the mechanisms underlying its intraspecific variation and (II) to identify candidate genes that are involved in temperature perception as well as yet unknown components of the HSFA1 signalling cascade in a genome-wide association study (GWAS). We will follow a two-step approach with an initial characterisation of HSR-related marker traits in 100 A. thaliana accessions that will result in the identification of extreme accessions and also allow for fine-tuning of the experimental conditions for the large-scale phenotyping at the second step. The identified extreme accessions will be characterised in detail at the metabolic and transcriptomic level using lipidomics and RNAseq. Transcription rates of selected differentially expressed genes will then be profiled across the 100 accessions and the data used for the generation of transcriptional networks resulting in the identification of the central regulatory elements underlying the observed intraspecific variation. At the second step, we will screen the temperature responsiveness of 1135 A. thaliana accessions whose genomes have been published recently thereby providing an excellent resource for GWA studies. The most significant candidate genes will be characterised and their exact role in temperature perception and acquired thermotolerance determined.Taken together, the proposed project will provide valuable insights into the molecular mechanism of temperature sensing as well as mechanisms of local adaptation to extreme temperatures.