AsWRKY44 represses the wound-induced sesquiterpene biosynthetic gene ASS1 expression in Aquilaria sinensis (Lour.) Gilg

Abstract

Abstract Agarwood is derived from wounded Aquilaria trees and is widely used in traditional medicine, incense, and perfume. Sesquiterpenes are one of the main active components in agarwood and are known to be induced by wounding or injury. The molecular mechanism by which wounding leads to sesquiterpene formation remains largely unknown. ASS1 is one of key enzymes responsible for the biosynthesis of sesquiterpenes and is a pivotal jasmonate (JA)-responsive wound-inducible synthase. However, why ASS1 does not express in healthy trees and how its expression is induced as a result of wounding remains unexplored. Here, we report that ASS1 is a wound-induced gene with a promoter in which the 242-bp (-973 to -731bp) region is identified as the core sequence for responding to wound signals. AsWRKY44 binds directly to this region and represses ASS1 promoter activity. Downregulation or disruption of AsWRKY44 can relieve the inhibition and activate ASS1 expression. Further, it is found that in response to the exogenous MeJA, AsWRKY44 is degraded and the expression of ASS1 is significantly upregulated. These findings confirm AsWRKY44 is a crucial negative regulator involved in the regulation of wound-induced ASS1 transcription, which reveals the core mechanism of agarwood sesquiterpenes biosynthesis.