CLAVATA

CLAVATA is a plant signaling pathway that controls the size of the shoot apical meristem (SAM) by restricting the number of stem cells. It was first described in the model plant Arabidopsis thaliana, where clavata mutants show enlarged meristems and fasciation of inflorescences, indicating a mechanism that limits stem cell proliferation.

The core components include CLV3, a small secreted peptide produced in the stem cell zone; CLV1, a leucine-rich repeat receptor-like kinase; and the CLV2-CRN (CORYNE) receptor-like complex. The CLV3 peptide moves from the central zone toward the outer layers and binds to CLV1 and the CLV2-CRN complex, triggering a signaling cascade that reduces the expression of WUSCHEL (WUS) in the organizing center. WUS, a transcription factor, promotes stem cell identity and, in turn, stimulates CLV3 expression, forming a negative feedback loop that maintains a stable SAM size.

Mutations that reduce CLV signaling lead to an expanded stem cell population and a larger SAM with more floral organs, whereas overexpression of CLV3 can shrink the meristem. The CLAVATA pathway is conserved across land plants, with homologous components and CLE peptides identified in diverse species. In maize, for example, CLV-like signaling involves FASCIATED EAR2 (FEA2) and related components, illustrating functional conservation in crop plants.

Biologically, CLAVATA is a key example of how stem cell homeostasis is achieved through intercellular signaling and feedback control. The pathway intersects with hormonal networks, including cytokinins and auxin, to coordinate meristem maintenance with organ formation and plant development.