The Function Of Arabidopsis CRY In Branching Regulation

Branch, which is developed from axillary bud, is an important developmental trait in agricultural and horticultural crops that determines the above-ground architecture of plants. Light is one of the major environmental factors influencing branch number. Cryptochromes(CRYs) are blue-light receptors that mediate various light responses in plants. However, the role of CRYs in branching regulation is not clear before this study. Here we uncover that cry1 mutants have more branch numbers than wild type Arabidopsis. To test if the abundant branching phenotype is due to CRY1 deficiency, we transformed 35S::CRY1 construct into cry1 mutant. The reults showed that CRY1 gain of function can rescue the branching phenotype in cry1 mutant. Moreover, the expression level CRY1 protein is negatively correlated with the branch number of transgenic plants. F1 plants(biallelic mutant) generated by hybridization between different cry1 allelic mutants also showed abundant branching phenotype, further confirming that CRY1 acts as a branching suppressor. To explore the mechanism of how CRY1 regulating branch number, we investigated the expression profile of genes associated with branching development. We found that the transcriptional level of PIF4 gene increased significantly in cry1 mutant. Taking together with the fact that the pif4/pif5 mutant shows less rosette branches than the WT, we conclude that CRY1 acts as a suppressor of branching through downregulation of PIF4 transcription.