The ratio of auxin to cytokinin controls leaf development and meristem initiation in Physcomitrium patens

Abstract

Crosstalk between auxin and cytokinin contributes to widespread developmental processes, including root and shoot meristem maintenance, phyllotaxy, and vascular patterning. However, our understanding of crosstalk between these hormones is limited primarily to angiosperms. The moss Physcomitrium patens (formerly Physcomitrella patens) is a powerful system for studying plant hormone function. Auxin and cytokinin play similar roles in regulating moss gametophore (shoot) architecture, as they do in flowering plant shoots. However, auxin-cytokinin crosstalk is poorly understood in moss. Here we find that the ratio of auxin to cytokinin is an important determinant of development in P. patens, especially during leaf development and branch stem cell initiation. Addition of high levels of auxin to P. patens gametophores blocks leaf outgrowth. However, simultaneous addition of high levels of both auxin and cytokinin partially restores leaf outgrowth, suggesting that the ratio of these hormones is the predominant factor. Likewise, during branch initiation and outgrowth, chemical inhibition of auxin synthesis phenocopies cytokinin application. Finally, cytokinin insensitive mutants resemble plants with altered auxin signaling and are hypersensitive to auxin. In summary, our results suggest that the ratio between auxin and cytokinin signaling is the basis for developmental decisions in the moss gametophore

Regulation of developmental gatekeeping and cell fate transition by the calpain protease DEK1 in Physcomitrium patens

“…4c and S 10 k) suggests that all positional and developmental queues discussed above are co-regulated in one DEK1-controlled CLAVATA regulon. Consistent with the findings from two recent studies 65 , 66 , our data suggests that this DEK1-controlled, cytokinin-mediated pathway governs stem-cell homeostasis acting separately from the cytokinin-independent pathway involving the RECEPTOR-LIKE PROTEIN KINASE2 (RPK2; subnetwork VIII).…”