3/27/2023 0 Comments Organ primordia![]() ![]() However, so far it was unclear how the number of stem cells is coordinated with the rate of organ production in the peripheral zone. WUS, in turn, increases the production of stem cells that generate CLV3. Together, they keep a protein called WUS (found in the deeper meristem known as the organizing zone) at low levels. This is regulated by a signalling pathway called CLV and a molecule produced by the stem cells in the central zone, called CLV3. A region in the plant called meristem, which can be found in the roots and shoots, continuously produces new organs in the peripheral zone of the meristem by maintaining a small group of stem cells in the central zone of the meristem. Stem cells are important precursor cells in plants (and animals) that can divide and specialize into other types of cells to help regrow leaves and flowers. For example, they can quickly adapt to their environment, and they can grow new organs, such as leaves and flowers, throughout their lifetime. Plants are sessile lifeforms that have evolved many ways to overcome this challenge. 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. Together, CLE40-BAM1-WUS establish a second negative feedback loop. CLE40 promotes WUS expression via BAM1, a CLV1-family receptor, and CLE40 expression is in turn repressed in a WUS-dependent manner. 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. How stem cell activity in the meristem centre is coordinated with organ initiation and cell differentiation at the periphery is unknown. 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. 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). Stem cell homeostasis in plant shoot meristems requires tight coordination between stem cell proliferation and cell differentiation. ![]()
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