Both blue light (BL) and auxin are essential for phototropism in Arabidopsis thaliana. However, the mechanisms by which light is molecularly linked to auxin during phototropism remain elusive.
Scientists in Dr. Chuanyou Li’s group from the Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences, found that PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5 transcription factors link blue light and auxin to regulate the phototropic response in Arabidopsis.
They demonstrated that PIF4 and PIF5 act downstream of the BL sensor, phototropin 1 (PHOT1), to negatively modulate phototropism in Arabidopsis. They also revealed that PIF4 and PIF5 negatively regulate auxin signaling. Further, they demonstrated that PIF4 directly activates the expression of the AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) genes IAA19 and IAA29 by binding to the G-box (CACGTG) motifs in their promoters. Genetic assays demonstrated that IAA19 and IAA29, which physically interact with AUXIN RESPONSE FACTOR7 (ARF7), are sufficient for PIF4 to negatively regulate auxin signaling and phototropism.
These results illuminate a key step of phototropic signaling in Arabidopsis by showing that PIF4 and PIF5 link light and auxin. Taken together, this study advances our understanding on the molecular mechanism underlying the phototropic response of plants.
This work with Dr. Jiaqiang Sun and Ph.D. Student Linlin Qi as the co-first authors has been published in
Plant Cell (
DOI:10.1105/tpc.113.112417). This research was supported by grants from the National Natural Science Foundation of China and Ministry of Science and Technology.
AUTHOR CONTACT:
Chuanyou Li, Ph.D.
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
CAS
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