Rice plant architecture largely determines rice grain yield. Plant hormones, including auxin, cytokinin and strigolactones (SLs), play critical roles in shaping rice plant architecture. Understanding the crosstalk between plant hormones is of great importance.
Researchers from Prof. LI Jiayang's group at the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences recently reveal the crosstalk between strigolactone and cytokinin according to a PNAS paper.
They have made great efforts in understanding the formation of rice plant architecture and the synthesis and signaling pathways of SLs. In previous study, they have identified D53 as the key repressor of SL signaling pathway in rice. But the SL-responsive genes working downstream of D53 remain to be identified.
In this study, they found that the treatment of rac-GR24, a synthetic analog of SL, can induce the expression of OsCKX9 (CYTOKININ OXIDASE/DEHYDROGENASE 9) in a D53-dependent manner.
They further revealed that OsCKX9 functions as a cytosolic and nuclear dual-localized CK catabolic enzyme and the overexpression of OsCKX9 suppresses the browning of d53 calli. In d53 mutant, expression levels of OsCKX9 are significantly decreased, and the levels of cytokinin are increased.
Moreover, OsRR5 is a secondary responsive gene of SLs, which can be repressed by the treatment of rac-GR24 depending on OsCKX9.
This study for the first time revealed the crosstalk between SLs and cytokinin in rice that SL could induce the expression of OsCKX9 to down regulate CK content which in turn triggers the response of downstream genes.
The work entitled "Strigolactone promotes cytokinin degradation through transcriptional activation of
CYTOKININ OXIDASE/DEHYDROGENASE 9 in rice" has been published online in
PNAS (
DOI:10.1073/pnas.1810980116).
The research was supported by National Natural Science Foundation of China, the National Key Research and Development Program of China, and the Strategic Priority Research Program.
Figure 1. Proposed model of the OsCKX9-mediated strigolactone signaling pathway (Image by IGDB)
Contact:
Mr. QI Lei
Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences
