MPF2-Like MADS-Box Genes Affecting Expression of SOC1 and MAF1 are Recruited to Control Flowering Time

A complex and intricate network of genes responding to various developmental and environmental signals control floral transition in plants. MADS-box genes are the key regulators and major contributors with regard to flowering time determination. Previously, MPF2-like genes belonging to the STMADS11 superclade were duplicated into MPF2-like-A and MPF2-like-B in Withania (WSA206 and WSB206) and Tubocapsicum (TAB 201). The present study was conducted to determine the effect of MPF2-like genes on flowering time by analyzing 35S:MPF2-like transgenic Arabidopsis plants as well as to probe their effects on the expression of SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1, a floral promoter) and MADS AFFECTING FLOWERING 1 (MAF1, a floral repressor) genes. The overexpression of WSA206 (35S:MPF2-like-A) moderately promoted flowering, while that of WSB206 and TAB 201 (35S:MPF2-like-B) exhibited no effects on floral transition. Concomitantly, an elevation in SOC1 transcript abundance and a reduction for MAF1 transcript levels were observed in 35S:WSA206 transgenic plants. Nucleotide diversity analysis indicated an extraordinary 8 aa extension at the C-terminus of the WSA206 protein. Ectopic expression of a truncated WSA206-version without these 8 aa (WSA206ΔC246) and of MPF2-like-B-versions elongated by these 8 aa (WSB206∇C257 and TAB 201∇C257) in Arabidopsis revealed an ambiguous role of the 8 aa signature in floral transition. It may influence a protein’s ability to modulate flowering time but is neither sufficient nor strictly necessary for early flowering. Nevertheless, the 8 aa extension influences the expression of SOC1 and MAF1 in MPF2-like derivative constructs. Our studies provide insight into the role of MPF2-like genes in phase transition by interacting with SOC1 and MAF1 genes, thereby also pointing to their significance as potential candidates for modifying flowering in crop plants in the future.