Proteomic Analysis of Isogenic Rice Reveals Proteins Correlated with Aroma Compound Biosynthesis at Different Developmental Stages

Fragrant rice has a potent flavor compound, 2-acetyl-1-pyrroline (2AP). A better understanding of the 2AP biosynthetic pathway is gained by proteomic analysis of two isogenic lines of Thai jasmine rice, Oryza sativa L. cv. Khao Dawk Mali 105, which differ only in the aromatic gene Os2AP. The protein profiles of two lines, from six growth stages, seedling to grain filling, had 41 identifiable protein spots. Four of these spots were betaine aldehyde dehydrogenase, a key enzyme responsible for 2AP production. This enzyme occurred in every growth stage of the non-aromatic rice line except smaller amount detected in the hard grain-filling stage of the aromatic line. Glyceraldehyde 3-phosphate dehydrogenase and aspartate aminotransferase, observed in the aromatic line, may involve in the metabolism of precursors for 2AP biosynthesis. In addition, glutamine synthetase and 1-cys peroxiredoxin A which function in ammonia reassimilation and hydrogen peroxide detoxification were unique in the aromatic line. However, proteins that correspond to photosynthesis and the nutrient reservoir were only detected in lower abundances. This possibly explains why the aroma rice grain weight is low. Our study proposed the possible role of these remarkable proteins which involved in 2AP biosynthesis in jasmine rice.