The highly interactive BTB domain targeting other functional domains to diversify the function of BTB proteins in rice growth and development.

The BTB (broad-complex, tram track, and bric-abrac) proteins are involved in developmental processes, biotic, and abiotic stress responses in various plants, but the molecular basis of protein interactions is yet to be investiagted in rice. In this study, the identified BTB proteins were divided into BTB-TAZ, MATH-BTB, BTB-NPH, BTB-ANK, BTB-Skp, BTB-DUF, and BTB-TPR subfamilies based on the additional functional domains found together with the BTB domain at N- and C-terminal as well. This suggesting that the extension region at both terminal sites could play a vital role in the BTB gene family expansion in plants. The yeast two-hybrid system, firefly luciferase complementation imaging (LCI) assay and bimolecular fluorescence complementation (BiFC) assay further confirmed that BTB proteins interact with several other proteins to perform a certain developmental process in plants. The overexpression of BTB genes of each subfamily in Arabidopsis revealed that BTB genes including OsBTB4, OsBTB8, OsBTB64, OsBTB62, OsBTB138, and OsBTB147, containing certain additional functional domains, could play a potential role in the early flowering, branching, leaf, and silique development. Thus we concluded that the presence of other functional domains such as TAZ, SKP, DUF, ANK, NPH, BACK, PQQ, and MATH could be the factor driving the diverse functions of BTB proteins in plant biology.