两种拮抗的 CLE 信号通路对拟南芥茎干细胞稳态的调控

植物茎分生组织中的干细胞稳态需要干细胞增殖和细胞分化之间的紧密协调。在拟南芥中，干细胞表达分泌型十二肽 CLAVATA3(CLV3) ，这种分泌型十二肽通过富亮氨酸重复受体激酶 CLAVATA1(CLV1)和相关的 CLV1家族成员下调同源结构域 WUSCHEL (WUS)的表达。WUS 蛋白从干细胞区域以下的细胞转移到分生组织顶端，促进干细胞的特性，连同 CLV3的表达，产生一个负反馈环。分生组织中心的干细胞活动如何与器官起始和周围的细胞分化相协调还不清楚。我们发现编码与 CLV3密切相关的分泌肽的 CLE40基因在分化细胞中以与 CLV3模式互补的方式在 SAM 中表达。CLE40通过 clv1家族受体 BAM1促进 WUS 的表达，而 CLE40的表达则以 WUS- 依赖的方式被抑制。CLE40-BAM1-WUS 共同建立了第二个负反馈回路。我们提出，干细胞内环境稳定是通过两种相互交织的通路来实现的，这两种通路通过 CLV3-CLV1调节 WUS 的活性并合并关于干细胞结构域大小的信息，通过 CLE40-BAM1调节细胞分化。

Stem cell homeostasis in plant shoot meristems requires tight coordination between stem cell proliferation and cell differentiation. In Arabidopsis, stem cells express the secreted dodecapeptide CLAVATA3 (CLV3), which signals through the leucine-rich repeat (LRR)–receptor kinase CLAVATA1 (CLV1) and related CLV1-family members to downregulate expression of the homeodomain transcription factor WUSCHEL (WUS). WUS protein moves from cells below the stem cell domain to the meristem tip and promotes stem cell identity, together with CLV3 expression, generating a negative feedback loop. How stem cell activity in the meristem centre is coordinated with organ initiation and cell differentiation at the periphery is unknown. We show here that the CLE40 gene, encoding a secreted peptide closely related to CLV3, is expressed in the SAM in differentiating cells in a pattern complementary to that of CLV3. CLE40 promotes WUS expression via BAM1, a CLV1-family receptor, and CLE40 expression is in turn repressed in a WUS-dependent manner. Together, CLE40-BAM1-WUS establish a second negative feedback loop. We propose that stem cell homeostasis is achieved through two intertwined pathways that adjust WUS activity and incorporate information on the size of the stem cell domain, via CLV3-CLV1, and on cell differentiation via CLE40-BAM1.

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