Proteomic analysis of common bean ( Phaseolus vulgaris L.) leaves showed a more stable metabolism in a variety responsive to biological nitrogen fixation

The common bean ( Phaseolus vulgaris L.) can supply part of its N demand through biological nitrogen fixation (BNF) in symbiosis with rhizobia. However, the responses to inoculation and BNF's contribution to plant nutrition vary with the plant genotype. Here, we examined the proteome of two common bean genotypes (Ouro Negro and BRS Radiante) to determine shifts in leaf metabolism with two N sources: mineral N and inoculation with Rhizobium tropici CIAT899 (= SEMIA 4077 = BR 322). Data are available via ProteomeXchange with the identifier PXD034817. Through UPLC-MS/MS analysis, we identified 917 proteins, 338 of which are differentially expressed. Here we focus on the 64 and 22 proteins differentially expressed in BRS Radiante and Ouro Negro, respectively, when comparing the proteome profiles of inoculated and N-fertilized plants. Different pathways in P. vulgaris were affected positively and negatively in BRS Radiante during symbiosis: glutathione metabolism, cysteine and methionine metabolism, phenylpropanoid biosynthesis, sulfur metabolism, peroxisome pentose and glucuronate interconversions, amino sugar and nucleotide sugar metabolism, carbon metabolism, and phagosome were the identified pathways. However, only three pathways were affected in Ouro Negro: peroxisome, endocytosis, and sulfur metabolism. Ouro Negro shows a less affected metabolism, which may lead to a more successful symbiosis. Proteins related to defense response were also induced in BRS Radiante, implying that their activation in this genotype may be partially responsible for its less efficient symbiosis. It is important to consider the difference in the life cycles of the two cultivars, as Ouro Negro had more time to adapt to the symbiosis than BRS Radiante. These results provide a basis for future studies to identify and explore biochemical mechanisms of nitrogen fixation in common beans beyond the roots.