植物类受体激酶调控根向水性反应的分子机理

Hydrotropism refers to that plant roots sense moisture gradient and grow towards higher water potential region. This process contributes significantly to plant water acquisition, especially in relatively drought environmental conditions. Using reverse genetic approaches, the applicant’s laboratory screened all 200 plus leucine-rich repeat receptor-like protein kinases (LRR-RLKs) from the Arabidopsis genome and identified one LRR-RLK, named as ARH1 for ALTERED ROOT HYDROTROPISM 1, which can authentically regulate root hydrotropism response. The roots of transgenic plants overexpressing ARH1 show drastically reduced response to moisture gradient whereas arh1 null mutant alleles exhibit significantly increased sensitivity to moisture gradient. Using a proteomic approach, the applicant’s group isolated another RLK, named as AAK1 for ARH1-ASSOCIATED KINASE 1, from a different RLK subfamily and a receptor-like cytoplasmic kinase (RLCK), designated as AAK2, both of which are putatively presented in the ARH1 complex. Genetic analyses demonstrated that both proteins mediate root hydrotropism. The goal of this proposal is to elucidate the molecular mechanisms of these uncharacterized proteins in regulating plant root hydrotropism and to unfold their associated signaling networks. These studies will contribute to our better understanding of plant root hydrotropism, and provide strategies to improve crop adaptations to drought conditions by using genetic engineering and breeding approaches in the near future.

根的向水性生长是指植物通过根尖感知土壤中水分梯度，向着水势较高区域生长的一种生物学特性，对植物从土壤中有效获取水分极为重要。利用反向遗传学手段，申请人课题组对拟南芥基因组中存在的所有200多个富含亮氨酸重复序列的类受体激酶进行了生物学功能分析，发现其中一个类受体激酶, ARH1，在植物根向水性反应中发挥重要功能。超表达ARH1使拟南芥根对水分梯度不敏感，而两个arh1突变体均表现出对水分梯度超敏感表型。利用蛋白组学技术，申请人课题组又找到了与ARH1互作的另一个类受体激酶, AAK1, 及一个类受体细胞质激酶，AAK2。遗传学分析证明它们在根的向水性反应中也起重要作用。本项目旨在通过一系列分子生物学手段阐明ARH1调控植物根向水性生长的分子机理及调控网络。该研究具有很高的理论价值，是植物学领域尚未解决的难点课题，对提高农作物适应干旱能力具有广阔的转化前景。

向水性反应是指植物根尖感受生长环境中的水势梯度并向着水势较高区域生长的生物学特性。这一特性对植物有效获取土壤水分至关重要，自发现以来持续受到科学界的热点关注。然而有关植物根尖向水性反应的分子机理仍未阐明，甚至对于向水性反应的一些基础性科学问题尚未解决。本研究发现受体激酶ARH1通过调控根尖分生区细胞分裂而调节根尖向水性生长，进一步研究发现细胞分裂素对根尖向水性反应起关键调控作用，水势梯度诱导细胞分裂素在根尖分生区单侧积累，从而特异的诱导细胞分裂素下游响应因子ARR16及ARR17在根尖分生区水势较低一侧积累表达，致使该侧根尖分生区细胞分裂活动加剧，产生更多的分生区细胞，诱导根尖朝向水势较高一侧弯曲生长。