Role of allene oxide cyclase in the regulation of rice phenolic acids synthesis and allelopathic inhibition on barnyardgrass

Jasmonic acid (JA) and methyl jasmonate are important endogenous signal molecules that can induce plant resistance to biotic and abiotic stresses. Allene oxide cyclase (AOC) is a key enzyme in the biosynthesis of jasmonates. Here, in order to evaluate the correlation between AOC transcript level and the allelopathic potential of rice, gene expression of AOC was genetic operated in allelopathic rice PI312777 and non-allelopathic rice Lemont, using RNA interference (RNAi) and overexpression (OX) techniques respectively. An increase in endogenous JA was found in AOC-OX rice, and the transcript levels of phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, hydroxylase, CoA-ligases, O-methyltransferases, and cinnamoyl alcohol dehydrogenases, which are involved in phenolic acid synthesis, were also up-regulated in AOC-OX transgenic rice when compared with those of the wild type. Higher accumulation of protocatechuic acid, p-hydroxy benzoic acid, ferulic acid, benzoic acid, 4-hydroxy-3-methoxybenzoicacid, and cinnamic acid content were found in the AOC-OX transgenic line. The increase of phenolic acids in the AOC-OX transgenic lines led to enhanced inhibitory rates on barnyardgrass, whereas the reverse was true in the AOC-RNAi transgenic line. The results suggest that AOC can regulate the synthesis of rice phenolic acids and thus allelopathic inhibition on barnyardgrass.