A proteomic study of the intermediate breakdown polypeptides of cowpea main storage protein β-vignin released in the spermosphere during seed germination

This study forms part of our ongoing research to characterize the molecular interplay between the structure and function of plant seed storage proteins (SPs) and their derived peptides. We aim to identify their physiological roles beyond merely providing nitrogen for seedlings, thereby enhancing our understanding of the multifunctionality of SPs. We investigated the accumulation and stability of proteolytic products generated from cowpea (Vigna unguiculata)'s primary storage protein, β-vignin. These products are transiently generated during germination and released from the seed within 48 hours of imbibition. To delve deeper into these phenomena, we incubated seeds in water at varying temperatures (4°C, 15°C, 25°C, and 35°C). Incubation temperature influences the types of polypeptides released, likely due to temperature-induced conformational changes in β-vignin, which modulate the regions exposed to proteolysis. Alternatively, temperature could tune the expression of different proteases, each with distinct specificities. The main released polypeptides have been characterized by mass spectrometry. Consistent with previous studies, this research expands our understanding of the molecular mechanisms underlying fine-tuning for environmental adaptation in resilient plants, such as cowpeas, during seed germination. Our current research focuses on elucidating the significant role of protein fragments released into the spermosphere.