The hormones auxin and cytokinin are essential for plant growth and development. Because of the central importance of root and shoot apical meristems in plant growth, auxin/cytokinin interactions have been predominantly analyzed in relation to apical meristem formation and function. In contrast, the auxin/cytokinin interactions during organ growth have remained largely unexplored. Here, we show that a specific interaction between auxin and cytokinin operates in both the root and the shoot where it serves as an additional determinant of plant development. We found that auxin at low concentrations limits the action of cytokinin. An increase in cytokinin level counteracts this inhibitory effect and leads to an inhibition of auxin signaling. At higher concentrations of both hormones, these antagonistic interactions between cytokinin and auxin are absent. Thus, our results reveal a bidirectional and asymmetrical interaction of auxin and cytokinin beyond the bounds of apical meristems. The relation is bidirectional in that both hormones exert inhibitory effects on each other's signaling mechanisms. However, this relation is also asymmetrical because under controlled growth conditions, auxin present in nontreated plants suppresses cytokinin signaling, whereas the reverse is not the case.
|State||Published - 2019|
Bibliographical noteFunding Information:
This work was supported by the USDA National Institute of Food and Agriculture, HATCH project 1009329, by the National Science Foundation (IOS-0919991), and by the Kentucky Tobacco Research and Development Center.
This work was supported by the USDA National Institute of Food and Agriculture, HATCH project 1009329, by the National Science Foundation (IOS-0919991), and by the Kentucky Tobacco Research and Development Center. We thank the Arabidopsis Biological Resource Center at Ohio State University for providing mutants axr3-1, axr3-3, arf7-1, and arf7-1 arf19-1, and transgenic lines ARR5p:GUS and DR5p:GUS. Dr. Atsuhiro Oka provided the arr1-1 line.
© 2019 The Authors.
- apical meristems
- hormonal antagonism
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Biochemistry, Genetics and Molecular Biology (miscellaneous)
- Plant Science