B-box transcription factor 28 regulates flowering by interacting with constans

Abstract

B-box transcription factors (BBXs) are important regulators of flowering, photomorphogenesis, shade-avoidance, abiotic and biotic stresses and plant hormonal pathways. In Arabidopsis, 32 BBX proteins have been identified and classified into five groups based on their structural domains. Little is known about the fifth group members (BBX26–BBX32) and the detailed molecular mechanisms relevant to their functions. Here we identified B-box transcription factor 28 (BBX28) that interacts with Constans (CO), a transcriptional activator of Flowering Locus T (FT). Overexpressing BBX28 leads to late flowering with dramatically decreased FT transcription, and bbx28 deficient mutant displays a weak early flowering phenotype under long days (LD), indicating that BBX28 plays a negative and redundant role in flowering under LD. Additionally, the interaction between BBX28 and CO decreases the recruitment of CO to FT locus without affecting the transcriptional activation activity of CO. Moreover, the N-terminal cysteines, especially those within the B-box domain, are indispensable for the heterodimerization between BBX28 and CO and activation of CO on FT transcription. Genetic evidences show that the later flowering caused by BBX28 overexpression is compromised by CO ectopic expression. Collectively, these results supported that BBX28 functions with CO and FT to negatively regulate Arabidopsis flowering, in which the N-terminal conserved cysteines of BBX28 might play a central role.

An Evolutionary Analysis of B-Box Transcription Factors in Strawberry Reveals the Role of FaBBx28c1 in the Regulation of Flowering Time

“…A flowering regulation pathway consisting of AtCO-AtFT-AtSOC has been established in Arabidopsis [53,54]. Our results show a downregulation of those genes in the overexpression lines, which suggests that FaBBX28c1 may function as an upstream negative regulator of the pathway (Figure 13), which is similar to its homologs in Arabidopsis [6]. In addition, recent works from strawberry also confirm the pathway of FvCO-FvFT1-FvSOC1 in the control of flowering time [10,55].…”

“…It is well understood that AtBBX19 plays dual roles in the regulation of flowering time in Arabidopsis and tolerance to drought stress in chrysanthemum [9,48]. However, the function of AtBBX28 remains contentious [6,7]. In the present study, the highest expression of FaBBX19 and FaBBX28 was also observed in the root tissue.…”

“…In addition, AtBBX28 can interact with AtCO (CONSTANS), which is a transcriptional activator of AtFT (Flowering locus T) in flowering time regulation pathway. Overexpression of AtBBX28 leads a late flowering phenotype with decreased AtFT expression, which indicates that AtBBX28 protein is a negative regulator of flowering time in Arabidopsis [6]. The impact of low ambient temperature on the function of AtBBX28 and AtBBX29 has been revealed.…”

Genome-Wide Characterization and Anthocyanin-Related Expression Analysis of the B-BOX Gene Family in Capsicum annuum L.

“…The CaBBX11 and CaBBX19 were under-expressed in leaves but over-expressed in other organs. While ABBX28 , the homologous gene of CaBBX28 encodes an atypical B-box domain protein that negatively regulates photomorphogenic development by interfering with the binding of the transcription factor, HY5, to its target gene promoters ( Liu et al, 2020c ). In this study, GO enrichment analysis indicated that CaBBX s of pepper were widely expressed and enriched spanning across all the stages of fruit development, and their functions were closely related to the differences in their domains, structures, promoters, and evolutionary processes.…”

Nuclear dynamics: Formation of bodies and trafficking in plant nuclei

“…In addition, some phyB photobodies may contain cryptochromes, which are blue light receptors (reviewed by van Buskirk et al, 2012). Apart from photoreceptors, the composition of the photobodies includes transcription factors, such as Constans (CO) and the B-box transcription factor 28 (BBX28), 10.3389/fpls.2022.984163 or the E3 ligase constitutively photomorphogenic 1 (COP1; Liu et al, 2014Liu et al, , 2020.…”