[Brassica juncea BjuWRKY71-1 accelerates flowering by regulating the expression of SOC1].

Brassica juncea (mustard) is a vegetable crop of Brassica, which is widely planted in China. The yield and quality of stem mustard are greatly influenced by the transition from vegetative growth to reproductive growth, i.e., flowering. The WRKY transcription factor family is ubiquitous in higher plants, and its members are involved in the regulation of many growth and development processes, including biological/abiotic stress responses and flowering regulation. WRKY71 is an important member of the WRKY family. However, its function and mechanism in mustard have not been reported. In this study, the BjuWRKY71-1 gene was cloned from B. juncea. Bioinformatics analysis and phylogenetic tree analysis showed that the protein encoded by BjuWRKY71-1 has a conserved WRKY domain, belonging to class Ⅱ WRKY protein, which is closely related to BraWRKY71-1 in Brassica rapa. The expression abundance of BjuWRKY71-1 in leaves and flowers was significantly higher than that in roots and stems, and the expression level increased gradually along with plant development. The result of subcellular localization showed that BjuWRKY71-1 protein was located in nucleus. The flowering time of overexpressing BjuWRKY71-1 Arabidopsis plants was significantly earlier than that of the wild type. Yeast two-hybrid assay and dual-luciferase reporter assay showed that BjuWRKY71-1 interacted with the promoter of the flowering integrator BjuSOC1 and promoted the expression of its downstream genes. In conclusion, BjuWRKY71-1 protein can directly target BjuSOC1 to promote plant flowering. This discovery may facilitate further clarifying the molecular mechanism of BjuWRKY71-1 in flowering time control, and creating new germplasm with bolting and flowering tolerance in mustard.

CsSPL13A directly binds and positively regulates CsFT and CsBAM to accelerate flowering in cucumber.

Flowering is an important developmental transition that greatly affects the yield of many vegetable crops. In cucumber (Cucumis sativus), flowering is regulated by various factors including squamosa promoter-binding-like (SPL) family proteins. However, the role of CsSPL genes in cucumber flowering remains largely unknown. In this study, we cloned the squamosa promoter-binding-like protein 13A (CsSPL13A) gene, which encodes a highly conserved SBP-domain protein that acts as a transcription factor and localizes to the nucleus. Quantitative real-time PCR (qRT-PCR) analysis showed that CsSPL13A was mainly expressed in flowers, and its expression level increased significantly nearing the flowering stage. Additionally, compared with the wild type(WT), CsSPL13A-overexpressing transgenic cucumber plants (CsSPL13A-OE) showed considerable differences in flowering phenotypes, such as early flowering, increased number of male flowers, and longer flower stalks. CsSPL13A upregulated the expression of the flowering integrator gene Flowering Locus T (CsFT) and the sugar-mediated flowering gene ß-amylase (CsBAM) in cucumber. Yeast one-hybrid and firefly enzyme reporter assays confirmed that the CsSPL13A protein could directly bind to the promoters of CsFT and CsBAM, suggesting that CsSPL13A works together with CsFT and CsBAM to mediate flowering in cucumber. Overall, our results provide novel insights into the regulatory network of flowering in cucumber as well as new ideas for the genetic improvement of cucumber varieties.

Brassica juncea BRC1-1 induced by SD negatively regulates flowering by directly interacting with BjuFT and BjuFUL promoter.

Flowering is crucial for sexual reproductive success in angiosperms. The core regulatory factors, such as FT, FUL, and SOC1, are responsible for promoting flowering. BRANCHED 1 (BRC1) is a TCP transcription factor gene that plays an important role in the regulation of branching and flowering in diverse plant species. However, the functions of BjuBRC1 in Brassica juncea are largely unknown. In this study, four homologs of BjuBRC1 were identified and the mechanism by which BjuBRC1 may function in the regulation of flowering time was investigated. Amino acid sequence analysis showed that BjuBRC1 contained a conserved TCP domain with two nuclear localization signals. A subcellular localization assay verified the nuclear localization of BjuBRC1. Expression analysis revealed that BjuBRC1-1 was induced by short days and was expressed abundantly in the leaf, flower, and floral bud but not in the root and stem in B. juncea. Overexpression of BjuBRC1-1 in the Arabidopsis brc1 mutant showed that BjuBRC1-1 delayed flowering time. Bimolecular fluorescent complementary and luciferase complementation assays showed that four BjuBRC1 proteins could interact with BjuFT in vivo. Notably, BjuBRC1 proteins formed heterodimers in vivo that may impact on their function of negatively regulating flowering time. Yeast one-hybrid, dual-luciferase reporter, and luciferase activity assays showed that BjuBRC1-1 could directly bind to the promoter of BjuFUL, but not BjuFT or BjuSOC1, to repress its expression. These results were supported by the reduced expression of AtFUL in transgenic Arabidopsis overexpressing BjuBRC1-1. Taken together, the results indicate that BjuBRC1 genes likely have a conserved function in the negative regulation of flowering in B. juncea.

[Expression of Brassica juncea BjuWRKY75 and its interactions with flowering integrator BjuFT].

Brassica juncea is a yearly or biennial vegetable in Brassica of Cruciferae. The yield and quality of its product organs are affected by flowering time. WRKY proteins family can respond to biological and abiotic stresses, developmental regulation and signal transduction. WRKY75 is an important member of WRKY family which can regulate flowering, but the flowering regulation mechanism in B. juncea has not been reported. In this study, a gene BjuWRKY75 in B. juncea was cloned, and the encoded-protein belonged to the group Ⅱ of WRKY protein with highly conserved domain. BjuWRKY75 had the highest homology with BriWRKY75 of Brassica nigra. The relative expression level of BjuWRKY75 in flowers was significantly higher than that in leaves and stems, and it was expressed stably in leaves. BjuWRKY75 protein was localized in the nucleus and interacted with the promoter of the flowering integrator BjuFT, which contained the W-box response element for the interaction between protein and DNA. Thus, it could transcriptionally activate the expression of the downstream genes. The overexpression of BjuWRKY75 in Arabidopsis led to earlier flowering significantly. In conclusion, BjuWRKY75 could directly target the promoter of BjuFT and accelerate flowering. These results may facilitate further study on the regulation of flowering molecules of BjuWRKY75.

[Mechanisms of alternative splicing in regulating plant flowering: a review].

Flowering is a critical transitional stage during plant growth and development, and is closely related to seed production and crop yield. The flowering transition is regulated by complex genetic networks, whereas many flowering-related genes generate multiple transcripts through alternative splicing to regulate flowering time. This paper summarizes the molecular mechanisms of alternative splicing in regulating plant flowering from several perspectives, future research directions are also envisioned.

[Molecular mechanisms of RPD3 family members in regulating plant development and environmental responses].

Lysine acetylation is one of the major post-translational modifications and plays critical roles in regulating gene expression and protein function. Histone deacetylases (HDACs) are responsible for the removal of acetyl groups from the lysines of both histone and non-histone proteins. The RPD3 family is the most widely studied HDACs. This article summarizes the regulatory mechanisms of Arabidopsis RPD3 family in several growth and development processes, which provide a reference for studying the mechanisms of RPD3 family members in regulating plant development. Moreover, this review may provide ideas and clues for exploring the functions of other members of HDACs family.