Arabidopsis B-BOX32 interacts with CONSTANS-LIKE3 to regulate flowering

Significance

Clock genes have been shown to be important in regulating many key agronomic traits. Therefore, identifying new players in this interconnected clock network will provide novel strategies toward developing new crop varieties. Our study identifies CONSTANS-LIKE 3 (COL3) as a critical protein-binding partner for B-BOX32 (BBX32) action in Arabidopsis. The discovery of the interaction with COL3 provides molecular clues as to how BBX32 exerts its effects on growth and yield. It also implicates COL3 as an integral protein-binding partner that can be used in combination with BBX32 for increased productivity. This regulatory pathway could be applied as an efficient strategy for genetic manipulation in crops for increased agricultural productivity.

Abstract

Plants have the ability to respond to seasonal environmental variations by monitoring day length to initiate flowering. The transition from vegetative to the reproductive stage is the critical developmental switch in flowering plants to ensure optimal fitness and/or yield. It has been previously reported that B-BOX32 ( BBX32) has the potential to increase grain yield when ectopically expressed in soybean. In the present study, we performed a detailed molecular characterization of the Arabidopsis B-box domain gene BBX32. We showed that the circadian clock in Arabidopsis regulates BBX32 and expressed in the early morning. To understand the molecular mechanism of BBX32 regulation, we performed a large-scale yeast two-hybrid screen and identified CONSTANS-LIKE 3 (COL3)/BBX4 as one of its interacting protein partners. Using different genetic and biochemical assays, we have validated this interaction and shown that COL3 targets FT in the presence of BBX32 to regulate the flowering pathway. Based on these findings, we hypothesized that this BBX32-COL3 module could be an additional regulatory mechanism affecting the reproductive development in Arabidopsis that could be translated to crops for increased agricultural productivity.