Expression analysis of phosphatase III-B subfamily in common bean reveals two storage proteins highly expressed during seed formation and germination

Abstract Germination and seedling development are crucial phases in the plant life cycle with economical and agronomical implications. During these stages, seedlings activate a wide range of strategies to ensure an adequate supply of nutrients and defence against environmental stress. The common bean phosphatase III-B subfamily comprises 11 genes, named PvNTD1 to PvNTD11 . Phylogenetic alignment with Arabidopsis thaliana III-B phosphatases identified PvNTD9, PvNTD10 and PvNTD11 as candidates Vegetative Storage Proteins (VSP) homologs. Among these, PvNTD9 and PvNTD10 exhibited high expression in developing seedlings, flowers and developing pods, tissues characterized by an intense mobilization and accumulation of nutrient. These genes showed different expression kinetics during post-germinative development, with PvNTD9 reaching maximum expression earlier than PvNTD10 , which suggests that their expression is not coordinated. To investigate its biochemical function, PvNTD9 was transiently overexpressed in Nicotiana benthamiana and purified. The recombinant protein lacked phosphatase activity, suggesting it may exert a function unrelated to enzymatic phosphate hydrolysis. Additionally, the expression of PvNTD9, PvNTD10 and PvNTD11 was strongly induced by methyl jasmonate treatment and mechanical wounding, supporting their potential roles as jasmonate-responsive VSPs. In this study we have identified two putative VSPs genes in common bean which are highly expressed in all seedling parts after germination. Furthermore, the expression of both genes follows a different temporal pattern. The possible physiological functions of these proteins during early development and stress responses are discussed.