In-depth proteomics to elucidate pathways associated with cross-tolerance to drought and aflatoxin tolerance in peanut seed

Droughts severely affect peanut yields and predispose the crops to Aspergillus invasion. Proteome analysis plays a critical role in functional genomics to better understand the molecular mechanisms of plant stress responses. This study aims to (i) determine differentially expressed proteins in drought-tolerant and susceptible genotypes in response to drought and fungal infestation and (ii) elucidate the proteins associated with cross-tolerance to both stresses.

Drought-tolerant and susceptible cultivars, ICGS76 and K1341, were subjected to drought stress via deficit irrigation. Additionally, the plants were challenged with A. parasiticus. Samples of peanut seeds were harvested from control, water-stressed, and fungal inoculated plants at regular time intervals to extract total proteins. The samples were subjected to overnight trypsin digestion, following LC-MS/MS analysis. Protein identification was carried out using ProteinPilot™ 5.0 software. Tandem mass spectrometry data collected for the peanut samples were searched against in silico tryptic digests of Viridiplantae proteins of the UniProt. Gene ontology analysis of identified proteins was carried out using Blast2GO v2.4.0.37 to annotate the protein sequences.

The study demonstrates that the ICGS76 genotype has 57 abundantly expressed proteins. In contrast, K1341 has 37 abundantly expressed proteins in double stressed treated peanut seed (drought and Aspergillus) and T1 and T2. ICGS-76 revealed 11 unique proteins such as ubiquitin, phosphoglycerate kinase, and late embryogenesis proteins involved in plant defense. Comparatively, seven unique proteins, including phosphoglucomutase, sucrose synthase, and tubulin, involved in metabolic and glycolytic related processes, were detected in K1341. Protein-protein interactions have revealed the presence of physical interactions between proteins involved in essential biological processes, including signal transduction, stress response, plant defense, metabolism, glycolysis, phosphorylation, and the activation and deactivation post-translational modification as well as assembly of the cytoskeleton. The expression and interaction of defense proteins in response to drought and Aspergillus infestation suggests cross-tolerance to both stresses.