Metabolite and transcriptome profiling of russeted and waxy apple skins highlighted genes involved in triterpene-hydroxycinnamate biosynthesis
Authors
C. M. Andre, S. Legay, S. Charton, J. Renaut, and J. F. Hausman
Reference
Planta Med, vol. 81, no. S 01, art. no. S1-S381, 2016
Description
Pentacyclic triterpenes possess numerous biomedical properties, including anti-inflammatory, anti-cancer, and anti-plasmodial activities. Esterification of triterpenic acids with hydroxycinnamic acids such as caffeic acid has been shown to increase their biological potential. In previous studies, we showed that russeted old heritage apple varieties are characterized by the accumulation of suberin in skin tissues, which present higher concentrations of specific triterpene esters such as betulinic acid-3-trans-caffeate as compared to their waxy-skinned counterparts. Knowledge on the molecular events associated with triterpene-caffeate production is however still lacking, although it could be therapeutically of major interest. For that purpose, apple fruits from two nearly isogenic yet contrasting varieties, i.e. 'Reinette du Canada Gris' (russeted skin) and 'Reinette du Canada Blanc' (waxy skin), were collected at five time points during the 2013 growing season. Metabolomics data were obtained by Ultra-Performance Liquid chromatography hyphenated with a high-resolution mass spectrometer (UPLC-TripleTOF HR-MS) and compared with whole gene expression profiling data (RNA-Seq).
For both cultivars, wax components (including triterpenes) increased until 99 days after full bloom (DAFB) and remained at the same level until commercial maturity (150 DAFB), while specific triterpene esters in russeted tissues continuously increased through fruit growth. This increase was associated with enhanced expression of suberin-related genes and of hydroxycinnamoyl-CoA transferases potentially implicated in triterpene-caffeates biosynthesis. The phenylpropanoid pathway appeared also differentially regulated, with higher amounts of hydroxycinnamic acid derivatives accumulating in russeted skins. Taken together, these results provide important information for the large scale in vitro production of specific apple triterpenes via bioengineering approaches.
