Progresses in biosynthesis pathway, regulation mechanism and potential application of 2-acetyl-1-pyrroline in fragrant rice

The formation of rice aroma is a complex process that is influenced by genetic and environmental factors. More than 500 fragrance compounds have been documented in fragrant rice, among which 2-AP dominates the aroma of rice. This paper introduced the identification of OsBadh2 in the biosynthesis of 2-AP in rice. Then, non-enzymatic and enzymatic pathways of the 2-AP biosynthesis have been comprehensively investigated. In detail, 2-AP biosynthesis-associated enzyme, such as OsBADH2, OsP5CS, OsGAD, OsGAPDH, OsProDH, OsOAT, OsODC and OsDAO, have been summarized, while MG and fatty acids are also implicated in modulating the biosynthesis of 2-AP by providing the acetyl groups. Moreover, extensive collections of traditional fragrant rice varieties have been collated, together with the OsBadh2 haplotypes of 312 fragrant rice germplasm in China. And finally, genetic engineering of OsBadh2 and other genes in the 2-AP biosynthesis to develop fragrant rice are discussed.