Comparative trascriptome profiling of jasmonate-treated versus control fruit in ripening peach (Prunus persica L. Batsch)

Jasmonic acid and its methyl ester (MJ) are cyclopentanonic compounds synthesized from α-linolenic acid. Allene oxide synthase (AOS) is the major control point of their biosynthetic pathway. JAs are signal molecules which elicit stress responses through JAs-induced proteins (JIPs); they are also involved in developmental processes, including fruit growth and ripening. In climacteric and non-climacteric fruit, endogenous JA levels are elevated during the early stages of fruit development, and then gradually decrease. In climacteric species (apple), JAs rise again at ripening. Exogenously applied on fruit, JAs induce biological effects mostly correlated with defence responses: they stimulate -carotene and anthocyanin accumulation, promote volatile emission, reduce chilling injury and increase disease resistance. However, their reciprocal relationships with ethylene are not well established; for instance, in apple, MJ stimulates ethylene production in pre-climacteric fruits while inhibits it in the climacteric ones. In the present study, MJ and its synthetic analogous n-propyl-dihydro-jasmonate (PDJ) were applied to peach branches (cv Stark Red Gold) at the S3 phase. In treated fruit, both chemicals inhibited climacteric ethylene production and delayed flesh softening. A microarray comparative trascriptome profiling of JA-treated versus control fruit indicated that MJ down-regulates genes positively involved in autocatalytic ethylene biosynthesis, thus confirming that JAs slow down ripening in peach fruit. On the contrary, MJ up-regulates several transcription factors and defence-related genes, among which JA biosynthetic genes, and differentially affected genes involved in cell-wall dismantling.