Wild and Cultivated Species of Rice Have Distinctive Proteomic Responses to Drought

Drought often compromises yield in non-irrigated crops such as rainfed rice, imperiling the communities that depend upon it as a primary food source. In this study, two cultivated species (Oryza sativacv. Nipponbare andOryza glaberrimacv. CG14) and an endemic, perennial Australian wild species (Oryza australiensis) were grown in soil at 40% field capacity for 7 d (drought). The hypothesis was that the natural tolerance ofO. australiensisto erratic water supply would be reflected in a unique proteomic profile. Leaves from droughted plants and well-watered controls were harvested for label-free quantitative shotgun proteomics. Physiological and gene ontology analysis confirmed thatO. australiensisresponded uniquely to drought, with superior leaf water status and enhanced levels of photosynthetic proteins. Distinctive patterns of protein accumulation in drought were observed across theO. australiensisproteome. Photosynthetic and stress-response proteins were more abundant in drought-affectedO. glaberrimathanO. sativa, and were further enriched inO. australiensis. In contrast, the level of accumulation of photosynthetic proteins decreased whenO. sativaunderwent drought, while a narrower range of stress-responsive proteins showed increased levels of accumulation. Distinctive proteomic profiles and the accumulated levels of individual proteins with specific functions in response to drought inO. australiensisindicate the importance of this species as a source of stress tolerance genes.