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

暴露在中等温度下会引起一种基因编码的热休克反应(HSR)，导致短期获得热耐性，使植物能够抵御随后的极端温度，这对未驯化的植物是致命的。HSR的特点是大量的转录和代谢重新编程，受到复杂的转录因子网络的严格调控。这个调控网络的中心是属于A1亚家族(HSFA1s)的热休克转录因子的激活。尽管HSR在分子水平上已经在拟南芥中得到了较好的描述，但仍然不清楚植物如何感知温度的升高，以及这一初始信号如何转化为HSFA1的激活。此外，关于拟南星天牛温度响应的自然变异及其潜在机制的知识也很有限。在我们的初步工作中，我们观察到了10个拟南芥材料在获得耐热性方面的显着差异。此外，植物存活与棉子糖的积累相关，棉子糖是一种依赖温度的三糖，其合成受到HSFA1的正调控，使其成为高铁开始的一个有希望的标记性状。基于这些观察，我们建议利用依赖温度的棉子糖积累来(I)深入了解HSFA1依赖的信号的遗传结构及其种内变异的机制，以及(Ii)在全基因组关联研究(Gwas)中识别与温度感知有关的候选基因以及HSFA1信号级联的未知成分。我们将遵循两步法，在100个拟南芥种质中初步鉴定与HSR相关的标记性状，这将导致极端种质的识别，并允许在第二步微调大规模表型的实验条件。我们将利用脂质组学和RNAseq在代谢和转录水平上对已鉴定的极端材料进行详细描述。选定的差异表达基因的转录速率将在100个种质中进行分析，并将用于生成转录网络的数据，从而确定支持所观察到的种内变异的中央调控元件。在第二步中，我们将筛选最近公布基因组的1135份拟南芥种质的温度响应性，从而为GWA研究提供良好的资源。将对最重要的候选基因进行表征，并确定它们在温度感知和获得性热耐受中的确切作用。综上所述，拟议的项目将为温度感知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.