THERMO-ROOT - A mechanistic analysis of root thermomorphogenesis in Arabidopsis thaliana

温度形态发生是指环境温度对植物形态发生的影响。适度升高的温度往往会刺激物种和组织的生长。地上部组织的热形态发生在生理和机制上已经有了较好的认识，但对根的热形态发生却缺乏全面的认识。从生态生理学的角度来看，茎部热形态发生增强了叶片的蒸发冷却，使植物在较高的环境温度下也能将光合活性保持在合理的内源温度范围内。生热促进根系生长可能与干旱反应密切相关，并使植物能够更快地到达更深的土层，从而获得更好的水分。我们的初步数据表明，根系能够独立于茎部感知温度变化。与茎部相反，生长促进不是通过温度诱导的细胞伸长激活实现的，而是通过增加细胞增殖实现的。我们有证据表明，生长素将温度信息传递给细胞周期，从而增加细胞在高温下的分裂率，从而产生更多的根细胞，从而促进初生根的生长。在这一建议中，我们建议研究生长素如何在高温下促进细胞增殖的机制细节。这包括a) 20°C和28°C生长的幼苗根尖单细胞RNA-seq数据集的生成，b)生长素通量的细胞生物学剖析和极性生长素运输机制响应温度变化的行为，以及C)调节分生组织细胞进入细胞周期的热敏成分的鉴定。总之，这个项目可能使我们能够从机制上理解根系温度形态形成信号下游的一个未知的根温度传感器。

Thermomorphogenesis describes the effect of ambient temperature on plant morphogenesis. Moderately elevated temperatures tend to stimulate growth across species and tissues. While thermomorphogenesis in above-ground shoot tissues is meanwhile fairly well understood on the physiological and the mechanistic level, root thermomorphogenesis lacks a comprehensive understanding. From an ecophysiological perspective, shoot thermomorphogenesis enhances evaporative leaf cooling which enable plants to keep photosynthetic activity within a reasonable endogenous temperature range, also in elevated ambient temperatures. Thermomorphogenic promotion of root growth may go hand in hand with drought responses and enable the plant to reach deeper soil layers with presumably better water access faster. Our preliminary data show that roots are able to sense temperature changes independent of the shoot. In contrast to the shoot, growth promotion is not achieved by temperature-induced activation of cell elongation but rather by increasing cell proliferation. We have evidence suggesting that auxin relays temperature information to the cell cycle, which increases cell division rates at elevated temperature, resulting in the production of more root cells and thereby promotion of primary root growth. In this proposal we suggest to investigate in mechanistic detail how auxin increases cell proliferation at high temperatures. This includes a) the generation of a single cell RNA-seq data set of root tips of 20°C vs. 28°C grown seedlings, b) cell biological dissection of auxin fluxes and the behavior of the polar auxin transport machinery in response to temperature changes, and c) identification of thermosensitive components that regulate entry of meristematic cells into the cell cycle. Together, this project may enable a mechanistic understanding of root thermomorphogenesis signaling downstream of a yet unknown root temperature sensor.