BPG3 is a novel chloroplast protein that involves the greening of leaves and related to brassinosteroid signaling

Abstract

Brassinosteroids are plant steroid hormones that regulate plant organs and chloroplast development. The detailed molecular mechanism for plant development by BR signaling is yet to be revealed, and many points regarding the relationship between BR signaling and chloroplast development remain unknown. We identify here the dominant mutant Brz-insensitive-pale green3-1D (bpg3-1D) from the Arabidopsis FOX lines that show reduced sensitivity to the chlorophyll accumulation promoted by the BR biosynthesis inhibitor, Brassinazole (Brz), in the light. BPG3 encodes a novel chloroplast protein that is evolutionally conserved in bacteria, algae, and higher plants. The expression of BPG3 was induced by light and Brz. The inhibition of electron transport in photosystem II of the chloroplasts was detected in bpg3-1D. These results suggest that BPG3 played an important role in regulating photosynthesis in the chloroplast under BR signaling.

Graphical Abstract

BR-inhibitor Brz activated chloroplast functions. bpg3 (Brz-insensitive-pale green3) mutant is disrupted in the signaling from BR-deficient condition to chloroplast activation.

Key words:

• brassinosteroid
• Brz
• signaling
• chloroplast regulator
• chemical biology

Acknowledgments

We thank Dr. Tsuyoshi Nakagawa (Shimane University) for presenting the gateway vector, pGWBs. This work was supported in part by the Program for Promotion of Basic Research Activities for Innovation Bioscience (PROBRAIN) to T. N. and T. A. and by the Core Research for Evolutional Science and Technology (CREST) Program to T. N. and T. A.

Notes

Abbreviations: BPG3, Brz-insensitive-pale green 3; BPG3-OX, BPG3 overexpressor; BL, brassinolide; BR, brassinosteroid; BRI1, brassinosteroid-insensitive 1; BZR1, brassinazole-resistant 1; CaMV, cauliflower mosaic virus; DET2, de-etiolated 2; DWF4, dwarf 4; MS, Murashige and Skoog; Brz, Brz220; FOX, full-length cDNA overexpressor.