Identification of the SHORT VEGETATIVE PHASE (SVP)-like MADS-box genes in pea (Pisum sativum L.)

SHORT VEGETATIVE PHASE (SVP)-like genes belonging to the StMADS11 subfamily of MADS-box transcription factors have important functions in the control of flowering time and floral organ specification and are thought to have been essential during angiosperm evolution. In this study, we identified the legume StMADS11 subfamily and examined the expression patterns of these SVP-like genes in the crop legume pea, under different photoperiod conditions and in key pea flowering mutants. We found three subclades of SVP-like genes represented in all legumes examined, including pea, common bean, soybean, Lotus japonicus and Medicago truncatula. These three subclades were also represented in other eudicot species. Legume SVPa genes fell within a eudicot SVP subclade that includes Arabidopsis SVP and tomato JOINTLESS (J), SVPb genes were found to be members of the StMADS11 subclade, and SVPc genes fell within the StMADS16/AGL24 subclade with the DORMANCY ASSOCIATED MADS-BOX (DAM) genes. In pea, we found SVP-like genes to be expressed in both leaf and apex tissues under inductive LD and non-inductive SD conditions. SVPc exhibited a clear developmental pattern of induction and downregulation under both conditions in both tissue types and showed misregulation in a mutant for the pea VEGETATIVE2 (VEG2) gene (an FD homolog), suggesting a possible role for SVPc in flowering, downstream of VEG2. The characterisation of legume SVP-like genes and expression analysis of the three pea SVP-like genes performed in this study provide a basis for further investigation of the function of these important transcription factors.