BIG regulates sugar response and C/N balance in Arabidopsis.

Mutations in gene not only produce pleiotropic phenotypes of plant development but also impair plant adaptive responses under various stresses. However, the role of gene in sugar signaling is not known. In this study, we first found that deficiency significantly sensitized the sugar-induced anthocyanin accumulation and the sugar-inhibited primary root growth, suggesting BIG is an important component of the sugar signaling pathway. Then we found that mutant plants had higher sugar levels compared with the wild type, indicating the involvement of gene in regulating plant sugar homeostasis. Importantly, we also found that the relative ratio of carbon to nitrogen (C/N) was greatly enhanced by deficiency. Overall, our work expands the known functionality of BIG and reveals its role in regulating sugar response and C/N balance. It is likely that BIG connects nutrient, light, and hormone signaling networks for regulating plant development and adaptive responses.