Transcriptome analysis of differentially expressed genes relevant to variegation in peach flowers.

Yingnan Chen,Yan Mao,Shuxian Li,Hailin Liu,Tongming Yin,Faxin Yu,Christian Schönbach

doi:10.1371/journal.pone.0090842

Abstract

BackgroundVariegation in flower color is commonly observed in many plant species and also occurs on ornamental peaches (Prunus persica f. versicolor [Sieb.] Voss). Variegated plants are highly valuable in the floricultural market. To gain a global perspective on genes differentially expressed in variegated peach flowers, we performed large-scale transcriptome sequencing of white and red petals separately collected from a variegated peach tree.ResultsA total of 1,556,597 high-quality reads were obtained, with an average read length of 445 bp. The ESTs were assembled into 16,530 contigs and 42,050 singletons. The resulting unigenes covered about 60% of total predicted genes in the peach genome. These unigenes were further subjected to functional annotation and biochemical pathway analysis. Digital expression analysis identified a total of 514 genes differentially expressed between red and white flower petals. Since peach flower coloration is determined by the expression and regulation of structural genes relevant to flavonoid biosynthesis, a detailed examination detected four key structural genes, including C4H, CHS, CHI and F3H, expressed at a significantly higher level in red than in white petal. Except for the structural genes, we also detected 11 differentially expressed regulatory genes relating to flavonoid biosynthesis. Using the differentially expressed structural genes as the test objects, we validated the digital expression results by using quantitative real-time PCR, and the differential expression of C4H, CHS and F3H were confirmed.ConclusionIn this study, we generated a large EST collection from flower petals of a variegated peach. By digital expression analysis, we identified an informative list of candidate genes associated with variegation in peach flowers, which offered a unique opportunity to uncover the genetic mechanisms underlying flower color variegation.

Highlights

Variegation in flower color is commonly observed in many plant species and occurs on ornamental peaches (Prunus persica f. versicolor [Sieb.] Voss)
From our EST collection, we were able to identify a number of highly expressed unigenes in peach flowers (Figure 3)
Because red flower color in peach is related to the synthesis of pelargonidin-based and cyanidin-based pigments, our results suggest that the low C4H, chalcone and stilbene synthase (CHS) and flavanone 3-hydroxylase (F3H) expression levels in white petals reduce DHK formation, thereby inhibiting pelargonidin and cyanidin production

Summary

Introduction

Variegation in flower color is commonly observed in many plant species and occurs on ornamental peaches (Prunus persica f. versicolor [Sieb.] Voss). Variegation in flower color is commonly observed in many plant species and occurs on ornamental peaches Most enzymes involved in the anthocyanin biosynthetic pathway have been identified in various plant species [5,6,7]. During the past few decades, much of the molecular information available on the regulation and biosynthesis of flower pigments has been derived from studies performed in model systems such as Zea mays L. An increasing number of non-classical plants, are providing unique insights into molecular mechanisms involved in flower pigment formation, leading to further understanding of how flower color varies among wild species [18,19,20]

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