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植物莖分生組織中的干細(xì)胞穩(wěn)態(tài)需要干細(xì)胞增殖和細(xì)胞分化之間的緊密協(xié)調(diào)。在擬南芥中，干細(xì)胞表達(dá)分泌型十二肽 CLAVATA3(CLV3) ，這種分泌型十二肽通過(guò)富亮氨酸重復(fù)受體激酶 CLAVATA1(CLV1)和相關(guān)的 CLV1家族成員下調(diào)同源結(jié)構(gòu)域 WUSCHEL (WUS)的表達(dá)。WUS 蛋白從干細(xì)胞區(qū)域以下的細(xì)胞轉(zhuǎn)移到分生組織頂端，促進(jìn)干細(xì)胞的特性，連同 CLV3的表達(dá)，產(chǎn)生一個(gè)負(fù)反饋環(huán)。分生組織中心的干細(xì)胞活動(dòng)如何與器官起始和周?chē)募?xì)胞分化相協(xié)調(diào)還不清楚。我們發(fā)現(xiàn)編碼與 CLV3密切相關(guān)的分泌肽的 CLE40基因在分化細(xì)胞中以與 CLV3模式互補(bǔ)的方式在 SAM 中表達(dá)。CLE40通過(guò) clv1家族受體 BAM1促進(jìn) WUS 的表達(dá)，而 CLE40的表達(dá)則以 WUS- 依賴(lài)的方式被抑制。CLE40-BAM1-WUS 共同建立了第二個(gè)負(fù)反饋回路。我們提出，干細(xì)胞內(nèi)環(huán)境穩(wěn)定是通過(guò)兩種相互交織的通路來(lái)實(shí)現(xiàn)的，這兩種通路通過(guò) CLV3-CLV1調(diào)節(jié) WUS 的活性并合并關(guān)于干細(xì)胞結(jié)構(gòu)域大小的信息，通過(guò) CLE40-BAM1調(diào)節(jié)細(xì)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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