Promoting seed decay is an ecological approach to reducing weed persistence in the soil seedbank. Previous work demonstrated that Fusarium avenaceum F.a.1 decays dormant Avena fatua (wild oat) caryopses and induces several defense enzyme activities in vitro. The objectives of this study were to obtain a global perspective of proteins expressed after F.a.1-caryopsis colonization by conducting proteomic evaluations on (i) leachates, soluble extrinsic (seed-surface) proteins released upon washing caryopses in buffer and (ii) proteins extracted from whole caryopses; interactions with aluminum (Al) were also evaluated in the latter study because soil acidification and associated metal toxicity are growing problems. Of the 119 leachate proteins classified as defense/stress, 80 were induced or repressed. Defense/stress proteins were far more abundant in A. fatua (35%) than in F.a.1 (12%). Avena defense/stress proteins were also the most highly regulated category, with 30% induced and 35% repressed by F.a.1. Antifungal proteins represented 36% of Avena defense proteins and were the most highly regulated, with 36% induced and 37% repressed by F.a.1. These results implicate selective regulation of Avena defense proteins by F.a.1. Fusarium proteins were also highly abundant in the leachates, with 10% related to pathogenicity, 45% of which were associated with host cell wall degradation. In whole caryopsis extracts, fungal colonization generally resulted in induction of a similar set of Avena proteins in the presence and absence of Al. Results advance the hypothesis that seed decay pathogens elicit intricate and dynamic biochemical responses in dormant seeds.
Keywords: aluminum toxicity; fungal pathogen; plant–microbe interactions; proteomics; weed biocontrol; weed seedbank; wild oat.