Peanuts are rich in essential nutrients, including proteins and antioxidants and are favoured by consumers seeking healthy food options. Peanut breeders are keen to develop cultivars with enhanced valuable functional food traits, in addition to disease resistance and high kernel yield potential. For example, peanut cultivars with high oleic acid content >75% have recently been developed by hybridisation using a naturally occurring mutant line developed by the University of Florida in the USA. In an effort to breed a stable peanut cultivar with enhanced antioxidant content, a population of recombinant inbred lines (RILs) was developed by the Australian Peanut breeding program through hybridisation by crossing a full season peanut genotype consistently expressing high antioxidant capacity (D147-p3-115) with another line consistently expressing low-mid level antioxidant capacity (Farnsfield).  

A subset of RILs (p27-272, p27-363, p27-036) showing very high and very low total antioxidant capacities and parent lines (D147-p3-115 and Farnsfield) were selected for proteomics analysis. A label-free quantitative shotgun proteomics approach coupled with nano-LC MS/MS was adopted to study functional proteins altered in peanuts with different antioxidant capacities. Due to the lack of the complete peanut genome, peptides were identified using a customised peanut protein sequence database..Statistically significant differentially expressed proteins between peanut lines with high and low antioxidant capacities were identified, and mapped to biological pathways. Protein abundance changes in biological pathways reveal the molecular fluctuations mediating cellular processes underlying each of the different RILs.  Potential protein biomarkers were identified for high antioxidant expressing peanut lines of Arachis hypogaea. These markers could help breeders in developing correlations between antioxidant responsive proteins and genes that account for the observed phenotype. This information could potentially enable breeders to integrate this with marker assisted selection for the breeding of high antioxidant cultivars.

Keywords: Peanuts, antioxidant capacity, Shotgun proteomics, nano LC-MS/MS, biomarker discovery.