Transforming the Snapdragon Aurone Biosynthetic Genes into Petunia Alters Coloration Patterns in Transgenic Flowers

Chen-Kuen Wang,Kin-Ying To,Po-Yen Chen,Yi-Chin Chin,Chih-Yu Lin

doi:10.4236/abb.2015.612073

Abstract

Aurones belong to a small class of flavonoids that provide yellow color in some floricultural plants including snapdragon. To explore novel flower coloration, two full-length cDNAs encoding chalcone 4'-O-glucosyltransferase (designated as SRY4'CGT) and aureusidin synthase (designated as SRYAS1) in the aurone biosynthetic pathway were cloned from yellow flowers of snapdragon (Antirrhinum majus cv. Ribbon Yellow). Binary vectors were constructed and transformed separately into Petunia hybrida harboring blue flowers. Only a few flowers in 4 out of 9 transgenic SRY4'CGT plants showed variegated blue-white sectors; as time passed, amounts of variegated flowers and proportion of white sectors in the background blue color of the new-born flowers gradually increased, until finally, the petal color was completely white in all late-born flowers. In contrast, a few flowers in 3 out of 13 transgenic SRYAS1 plants showed variegated blue-white sectors; but, the amounts of variegated flowers did not increase over the whole flowering stage, and no complete white flowers were observed. RNA samples isolated from blue and white sectors of T1 transgenic SRY4'CGT plants were analyzed by reverse transcription-PCR, transgenic SRY4'CGT transcripts were detected in both sectors; however, transcripts of an upstream gene, chalcone synthase (CHS), were abundantly detected in the blue sectors but largely reduced in the white sectors, suggesting that the expression of CHS gene was suppressed in white sectors of transgenic plants. Furthermore, HPLC coupled with mass spectrometry demonstrated cyandin, malvidin and their derivatives were absent in white sectors, causing the white phenotype. Our findings may be attractive to molecular breeders.

Highlights

Aurones belong to a small class of flavonoids that provide yellow color in some floricultural plants including snapdragon
THC is converted into naringenin by chalcone isomerase (CHI), and naringenin is further converted into different kinds of anthocyanins, flavonols and flavones by several enzymes in the flavonoid biosynthesis pathway
Our clone is the same length as the published A. majus Am4'CGT nucleotide sequence ([11]; GenBank accession No AB198665); it differed from the published clone by 16 nucleotides and 8 amino acids (Figure 2)

Summary

Introduction

Aurones belong to a small class of flavonoids that provide yellow color in some floricultural plants including snapdragon. Over the past few decades, almost all the key genes in the main biosynthesis pathways of flavonoids and carotenoids have been cloned from a range of plant species, and genetic engineering has been carried out to breed new cultivars with novel flower colors in many floricultural plants [2]-[8]. THC is converted into naringenin by chalcone isomerase (CHI), and naringenin is further converted into different kinds of anthocyanins, flavonols and flavones by several enzymes in the flavonoid biosynthesis pathway In yellowflowering plants such as snapdragon, THC is converted into THC 4'-O-glucoside by UDP-glucose: chalcone 4'-O-glucosyltransferase (4'CGT), and THC 4'-O-glucoside is further converted into aureusidin 6-O-glucoside (yellow pigment) by aureusidin synthase (AS) [11]. The findings reported will be useful for breeding new cultivars with attractive coloration patterns

Methods

Results

Conclusion