Strigolactones (SLs), a class of carotenoid-derived plant hormones, repress plant branching and regulate other developmental processes. In rice, branching is also known as tillering and tiller number is an important factor in determining the grain yield. SLs repress the tiller number by inhibiting tiller bud outgrowth to regulate rice architecture.
Several components have been characterized, D14, the receptor of SLs, D3, the F-box protein in SCF E3 ligase complex and D53, the substrate of D3 and a repressor of SL signaling, but little is known of the D53-downstream mechanism in SL signaling.
Researchers from Prof. LI Jiayang's group at the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences recently found that Ideal Plant Architecture 1 (IPA1) is the long-speculated direct downstream transcription factor repressed by D53 in SL signaling in rice.
They have made great efforts in understanding the formation of rice plant architecture and the synthesis and signaling pathways of SLs.
In previous studies, they have characterized a key gene in regulating rice plant architecture, IPA1, which encodes a SBP-box-containing transcription factor and has pleiotropic roles in the regulation of growth the development. They have revealed that D53 is the substrate of D3 and functions as the key repressor of SL signaling.
In the study, they found that loss-of-function mutants of ipa1 exhibits high tillering phenotypes and were insensitive to the exogenously applied rac-GR24, a synthetic analog of SL, indicating that IPA1 plays an important role in SL signaling. D53 could interact with IPA1 in vivo and in vitro, and suppresses the transcriptional activation activity of IPA1.
In addition, IPA1 could bind to the D53 promoter and form a feedback regulation. These results showed that IPA1 is the direct D53-downstream transcription factor in SL signaling in rice tillering determination.
This study not only extends our understanding of SL signaling in rice, but also provides a powerful tool for molecular breeding in rice.
The research was supported by the National Key Research and Development Program of China, National Natural Science Foundation of China and the Strategic Priority Research Program "Molecular Mechanism of Plant Growth and Development".
The role of IPA1 in SL signaling in rice. (Image by IGDB)
