Candidate proteins associated with popping expansion capacity of popcorn
The mechanical resistance of the popcorn pericarp has a positive and direct relationship to its expansion volume. It allows enough time for the endosperm to gelatinize completely before its extravasation. Expansion is a polygenic trait that has been extensively studied. However, no records in the literature indicate proteins that directly affect pericarp thickness and integrity. Therefore, the present work aimed to identify candidate pericarp proteins associated with the expansion capacity of popcorn kernels using the shotgun proteomic approach. The analyses were carried out in the pericarp of two popcorn inbred lines, P11 (expansion volume of 30 mL g-1) and P16 (expansion volume of 14 mL g-1), in two developmental stages (15 and 25 DAP). A total of 803 non-redundant proteins were identified. Most of them were involved in key processes associated with pericarp development and thickening. Two candidate proteins stood out among the differentially abundant proteins. Peroxidase was up-accumulated in P11/25 DAP (high popping expansion) and was 1.498 times more abundant in this inbred line, while xyloglucan endotransglucosylase/hydrolase was more abundant in P16 (low popping expansion) in both developmental stages. Thus, the peroxidase protein increases expandability, whereas xyloglucan endotransglucosylase/hydrolase decreases it, even though its specific role has not been elucidated. These proteins should be further investigated, as they may be used to improve expansion capacity in popcorn breeding programs.