The B-box transcription factor BBX5 enhances ultraviolet-B resistance by promoting anthocyanin biosynthesis in
Yibin Liang1, Yarou Xu1, Chuanglie Lin1
1Guangdong Basic Research Center of Excellence for Precise Breeding of Future Crops, Guangdong Provincial Key Laboratory for the Development Biology and Environmental Adaptation of Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
Abstract:
Ultraviolet-B (UV-B) light, a natural component of sunlight, plays a crucial role in the regulation of plant growth and development. B-box (BBX) proteins are zinc-finger transcription factors essential for plant growth, development, and responses to abiotic stress. The role of BBX5 in UV-B stress responses has not been previously identified. Here, we identify BBX5 as a novel regulator of UV-B stress tolerance in Arabidopsis. Firstly, UV-B treatment significantly induced the expression of BBX5. Transcriptome analyses revealed that BBX5 was associated with the anthocyanin biosynthesis pathway. Phenotypic analysis showed that bbx5 mutant exhibited heightened UV-B sensitivity and reduced anthocyanin levels under UV-B exposure, whereas BBX5-overexpressing lines displayed increased anthocyanin content and enhanced UV-B resilience. Mechanistically, BBX5 directly interacts with the promoter of anthocyanidin synthase (ANS), thereby stimulating its expression. HY5, a key regulator in UV-B signaling, enhances the expression of BBX5 by binding to its promoter region. Genetic analysis showed that BBX5 overexpression partially restored anthocyanin levels and improved UV-B resistance in hy5-215 mutant. Our study highlights the crucial role of the HY5-BBX5-ANS regulatory axis in modulating anthocyanin biosynthesis and UV-B acclimation in Arabidopsis.
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