Identification of differential proteins of mungbean cotyledons during seed germination: a proteomic approach

Proteomic analyses of seed germination, a complex physiological process is not yet explored in leguminous plants. Such study has been undertaken to reveal the variations that occur in cotyledonary proteins during seed gemination of mungbean (Vigna radiata L. Wilczek). Cotyledons were harvested for protein extraction and two dimensional gel electrophoreses at two developmental stages (I and II) of seed germination. Comparative qualitative and quantitative analyses between these two stages revealed differential expressions and de novo appearance or disappearance of proteins. Seventy-four proteins were identified by MALDI-TOF-MS and MS/MS and categorized according to their functions including metabolism and energy production, stress related, protein processing, transcription, storage etc. Majority of these proteins are associated with metabolisms indicating that cotyledons acquire an active metabolic state during seed germination. Many of the identified proteins were enzymes involved in starch and sucrose metabolism and those of glycolysis, tricarboxylic acid cycle etc. A pathway illustrating starch synthesis/breakdown, degradation of sucrose and the fates of reducing sugars in the germinating mungbean cotyledons has been elucidated. Predominance of antioxidant enzymes can be attributed to combat with reactive oxygen species generated due to active metabolism. Thus, the study comprehensively dealt with mechanisms of stored reserve mobilization and the roles of additional cotyledonary proteins of mungbean essential for successful seed germination and seedling development.