CLSM data of CLE40, CLV3, WUS, BAM1, and CLV1 reporter lines in Arabidopsis thaliana

Stem cell homeostasis in plant shoot meristems requires tight coordiantion
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.