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 Physcomit...

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Bibliographic Details
Published in:Journal of experimental botany 2023-11, Vol.74 (21), p.6541-6550
Main Authors: Cammarata, Joseph, Roeder, Adrienne H K, Scanlon, Michael J
Format: Article
Language:English
Subjects:
Bryophyta
Bryopsida - genetics
Cytokinins - pharmacology
Hormones
Indoleacetic Acids - pharmacology
Meristem
Plant Leaves
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Summary: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, to those 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. We demonstrate that the ratio of the amounts of plant hormones auxin and cytokinin, and not their absolute concentrations, ultimately regulates leaf development and stem cell initiation in Physcomitrium patens.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erad299