Abstract
B-box (BBX) zinc finger proteins play critical roles in both vegetative and reproductive development in plants. Many BBX proteins have been identified in Arabidopsis thaliana as floral transition regulatory factors, such as CO, BBX7 (COL9), BBX19, and BBX32. BBX32 is involved in flowering time control through repression of COL3 in Arabidopsis thaliana, but it is still elusive that whether and how BBX32 directly interacts with flowering signal integrators of AGAMOUS-LIKE 24 (AGL24) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) in Chinese cabbage (Brassica rapa L. ssp. pekinensis) or other plants. In this study, B-box-32(BBX32), a transcription factor in this family with one B-box motif was cloned from B. rapa, acted as a circadian clock protein, showing expression changes during the circadian period. Additional experiments using GST pull-down and yeast two-hybrid assays indicated that BrBBX32 interacts with BrAGL24 and does not interact with BrSOC1, while BrAGL24 does interact with BrSOC1. To investigate the domains involved in these protein-protein interactions, we tested three regions of BrBBX32. Only the N-terminus interacted with BrAGL24, indicating that the B-box domain may be the key region for protein interaction. Based on these data, we propose that BrBBX32 may act in the circadian clock pathway and relate to the mechanism of flowering time regulation by binding to BrAGL24 through the B-box domain. This study will provide valuable information for unraveling the molecular regulatory mechanisms of BrBBX32 in flowering time of B. rapa.
Highlights
Flowering in plants is mediated by multiple endogenous genetic pathways and multiple exogenous environmental factors to guarantee that it occurs at the most appropriate time of the plant life cycle (He and Amasino, 2005; Bluemel et al, 2015; Song et al, 2015a)
Sequence analysis of BrBBX32, BrSOC1 and BrAGL24 We used homologous cloning to obtain the sequences of BrB-Box32 (BrBBX32), BrSOC1 and BrAGL24, encoding proteins of 230, 213 and 216 amino acids, respectively
We have demonstrated that BrBBX32 interacts with BrAGL24 and that BrAGL24 interacts with BrSOC1 in B. rapa by yeast two-hybrid and glutathione S-transferase (GST) pull-down assays
Summary
Flowering in plants is mediated by multiple endogenous genetic pathways and multiple exogenous environmental factors to guarantee that it occurs at the most appropriate time of the plant life cycle (He and Amasino, 2005; Bluemel et al, 2015; Song et al, 2015a). The intricate network of these pathways controls the floral transition via transcriptional regulation of several floral integrators, including SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1(SOC1), SHORT VEGETATIVE PHASE (SVP), FLOWERING LOCUS C (FLC), FLOWERING LOCUS T (FT), LEAFY (LFY), FRUITFULL (FUL), AGAMOUS-LIKE 24 (AGL24) and CONSTANS (CO) (Boss et al, 2004; Parcy, 2004; Yoo et al, 2005; Mateos et al, 2015). The complex networks formed by the interactions of these pathways control the process of flowering through the transcriptional regulation of gene expression in several flowering pathways. As a downstream target of CONSTANS (CO), SOC1 is directly activated by CONSTANS (CO) under long-day (LD) conditions and regulates LFY (LEAFY) expression in the gibberellic acid (GA) pathway through direct binding to the LFY promoter (Seo et al, 2009; Lee and Lee, 2010).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
