Protein interactions of SOC1 with SVP are regulated by a few crucial amino acids in flowering pathways of Brassica juncea

Abstract

SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) is a vital flowering signal integrator to promote flowering, which is inhibited by a MADS-box transcription factor, SHORT VEGETATIVE PHASE (SVP). However, it remains elusive about how SOC1 interacts with SVP in flowering pathways of Brassica juncea. Here, B. juncea SOC1 (BjuSOC1) gene was cloned and it expressed differently between stem apexes and leaves during the low-temperature vernalization and long-day photoperiod pathways. Yeast two-hybrid and BiFC assays indicated that BjuSOC1 directly interacted with BjuSVP in vitro and in vivo. Interestingly, further studies indicated that mutants of BjuSOC1K108V, BjuSOC1R109L, BjuSOC1C137K could no more interact with BjuSVP, and BjuSVPR137L also led to loss of the protein interaction. It suggested that the 108th, 109th, and 137th of BjuSOC1 and 137th of BjuSVP regulated the protein interactions between BjuSOC1 and BjuSVP. The results provided valuable information for further study on the control of flowering time in B. juncea.