受体激酶CIKs调控拟南芥根端分生组织稳态的分子机理

Receptor kinases locate on cell surface to perceive signals from environment and the surrounding cells, and transduce signals into the cell to regulate plant growth, development and response to environment. Model plant Arabidopsis has more than 610 receptor kinases. However, the biological functions of most of these receptor kinases have not been revealed. Reverse genetics was employed to investigate the functions of one subfamily, CLAVATA1 INSENSITIVE RECEPTOR KINASES (CIKs). Our preliminary studies indicated that loss-of-function of these CIKs resulted in defective root apical meristem (RAM), which is very similar to the phenotypes of clv1, crn, bam1, bam3, rpk2 and acr4 mutants. Based on the preliminary results, the current project proposes to test whether CIKs form protein complexes with other receptor kinases, such as CLV1, CRN, BAM1, BAM3, RPK2 and ACR4, to mediate peptide signals for RAM maintenance. Downstream interacting proteins and new genes involved in CIKs-mediated RAM maintenance will be screened and characterized, and finally to reveal the molecular mechanisms regulating the homeostasis of RAM by CIKs.

受体激酶位于细胞膜上感知外界环境和周围细胞的信号，将信号跨膜传递到胞内调控植物的生长发育和对环境的反应。模式植物拟南芥有超过610个受体激酶，其中大部分受体激酶的生物学功能都没有得到深入阐述。我们利用反向遗传学的方法，发现其中一个亚家族CIK缺失后，拟南芥的根近端和远端分生组织异常，与受体激酶CLV1、CRN、BAM1、BAM3、RPK2和ACR4缺失后的表型相似。本项目将在已有的工作基础上，证明CIKs可能分别与上述受体激酶形成受体复合物，介导多肽信号调控根近端和远端分生组织的稳态，寻找在根端分生组织稳态维持过程中与CIKs相互作用的蛋白质，筛选与CIKs一起调控根端分生组织稳态的新基因，揭示CIKs调控根端分生组织稳态的分子机理。

植物体内存在两大类初级分生组织：茎端分生组织和根端分生组织。它们分别介导了植物地上和地下部分的形态建成。根端分生组织包括根近端分生组织和根远端分生组织，分别对于根的伸长和根冠结构的维持非常重要。我们之前的工作表明CIKs (CLV3 INSENSITIVE KINASES)调控茎端分生组织的稳态维持，但它是否也在根端分生组织中发挥作用并不清楚。通过一系列遗传生化实验，我们发现CIKs作为保守的调控元件同样参与了根端分生组织的稳态维持。在根远端分生组织的稳态维持中，ACR4与CIKs形成受体–共受体复合物，共同感知CLE40的信号，并通过磷酸化传递信号，最终抑制WOX5的表达来促进根冠原细胞的分化。而在根近端分生组织的调控中，我们发现CIKs位于BRX和OPS信号通路中调控原生韧皮部的分化，而且BAM1与BAM3功能冗余地调控原生韧皮部的分化，首次揭示了调控这一过程的配体CLE25/26/45，并明确了CLE25/26/45–BAM1/3–CIK2/3/4/5/6信号模块位于BRX和OPS的下游促进原生韧皮部的分化，进而调控根近端分生组织的稳态。