Proteomic analysis in common bean seed coat reveals high enzymatic profile with relevance for purine nucleotide metabolism during germination

Common bean is a major legume crop with high seed protein content and significant global importance for human consumption. Seedling establishment is a critical stage for plant survival, as the plant must develop in a potentially hostile environment where the seed coat or testa plays a crucial role. In this manuscript, we performed a proteomic study of bean seed coats and compared protein levels before and after germination. We found a significant number of proteins in the seed coat, of which 919 increased in abundance during germination, 717 decreased, and 1,567 remained unchanged. Among the various protein categories that increased in abundance, the nucleoside diphosphate kinase (NDPK) family and T2 ribonucleases, proteins involved in nucleotide metabolism, were used to analyse the transcript-translation relationship. In common bean, there are four NDPKs, three of which have been identified in the bean seed coat at both the protein and mRNA levels, and 13 ribonucleases T2, five of which have been identified as proteins and four as genes. The purine nucleotide degradation pathway in the seed coat has also been analysed, identifying proteins that could catalyze the degradation of these nucleotides to ureides. Overall, the data presented allow us to conclude that the seed coat is a functionally active tissue during germination and does not simply act as a protective barrier. Moreover, the proteomic profile reveals that this tissue exhibits a high nucleotide metabolic rate.