Synthesis of flavour‐related linalool is regulated by PpbHLH1 and associated with changes in DNA methylation during peach fruit ripening

Abstract

Linalool is one of the common flavour-related volatiles across the plant kingdom and plays an essential role in determining consumer liking of plant foods. Although great process has been made in identifying terpene synthase (TPS) genes associated with linalool synthesis, much less is known about regulation of this pathway. We initiated study by identifying PpTPS3 encoding protein catalysing enantiomer (S)-(+)-linalool synthesis, which is a major linalool component (~70%) observed in ripe peach fruit. Overexpression of PpTPS3 led to linalool accumulation, while virus-induced gene silencing of PpTPS3 led to a 66.5% reduction in linalool content in peach fruit. We next identified transcription factor (TF) PpbHLH1 directly binds to E-box (CACATG) in the PpTPS3 promoter and activates its expression based on yeast one-hybrid assay and EMSA analysis. Significantly positive correlation was also observed between PpbHLH1 expression and linalool production across peach cultivars. Peach fruit accumulated more linalool after overexpressing PpbHLH1 in peach fruit and reduced approximately 54.4% linalool production after silencing this TF. DNA methylation analysis showed increased PpTPS3 expression was associated with decreased 5 mC level in its promoter during peach fruit ripening, but no reverse pattern was observed for PpbHLH1. Arabidopsis and tomato fruits transgenic for peach PpbHLH1 synthesize and accumulate higher levels of linalool compared with wild-type controls. Taken together, these results would greatly facilitate efforts to enhance linalool production and thus improve flavour of fruits.

Diversity and Functional Evolution of Terpene Synthases in Rosaceae

“…As a result, hundreds of complete TPSs that contained both domains were identified. A recent study used this similar approach to detect TPSs in peach [2], and it detected 38 full-length TPSs with both domains; another study detected cultivated apple contained 55 putative TPS genes [4], the similar amount of TPSs as our results indicates the approach used in our study is reliable. For each Rosoideae species, we found that a certain ratio (64.29-0%) of putative TPSs was composed of both domains.…”

“…On the whole, the above finding indicated that TPSs in Rosaceae also underwent extensive expression differentiation after the split of sister lineages and gene duplication. thases; their product s-linalool is assumed to be an important flavor component in P. persica [2]. On the whole, the above finding indicated that TPSs in Rosaceae also underwent extensive expression differentiation after the split of sister lineages and gene duplication.…”

“…Plants 2022, 11, 736 2 of 19 Terpenoid compounds have been characterized in almond, apple, and peach [2][3][4][5]. Volatile compounds in almond (plum subfamily) mainly consist of fatty acid-derived volatiles, several monoterpenes, sesquiterpenes, and phenylpropanoids, and significant differences in volatile composition were observed between different tissues and various varieties [3].…”

Molecular Insights of Fruit Quality Traits in Peaches, Prunus persica

“…Linalool, an acyclic monoterpene that also imparts sweet, floral, alcoholic note, and terpene synthases (TPSs), is the vital enzyme involved in the formation of linalool [ 49 ]. Wei et al identified that overexpression PpTPS3 led to the accumulation of linalool while gene silencing led to 66.5% linalool reduction in peach [ 50 ]. In addition, transcription factor PpbHLH1 activated PpTPS3 by directly binding to its promoter region, validating its role in linalool accumulation [ 50 ].…”

“…Wei et al identified that overexpression PpTPS3 led to the accumulation of linalool while gene silencing led to 66.5% linalool reduction in peach [ 50 ]. In addition, transcription factor PpbHLH1 activated PpTPS3 by directly binding to its promoter region, validating its role in linalool accumulation [ 50 ]. Another study showed that UV-B irradiation reduced linalool production through modulation of terpene synthase gene ( PpTPS1 ) [ 51 ].…”