Sequence differences in LcFGRT4 alleles are responsible for the diverse anthocyanin composition in the pericarp of Litchi chinensis.

Glycosylation plays a major role in the diversity in the chemical compositions of flavonoids. In this study, we performed biochemical and molecular assays to identify a glucosyltransferase gene responsible for the anthocyanin composition in litchi. Cyanidin-3-glucoside and cyanidin-3-rutinoside were predominant anthocyanins in the red pericarp and young leaf of litchi. Anthocyanin composition varied among litchi varieties. Anthocyanin profile was primarily determined by genetic factors. Higher activities of UDP-rhamnose: cyanidin-3-glucoside rhamnosyltransferase (CGRT) were detected in the pericarps of the cyanidin-3-rutinoside predominant varieties. Three full-length putative UDP-rhamnose: flavonoid glycoside 2″-O-beta-l-rhamnosyltransferase-like genes were isolated and designated as LcFGRT2, LcFGRT4, and LcFGRT5. Phylogenetic analysis showed that these genes were clustered with other glucoside-glycosyltransferases. Notable activities in catalyzing cyanidin-3-rutinoside formation were observed in extracts of tobacco leaves and yeast with heterologous expression of LcFGRT4. However, the expression pattern of LcFGRT4 did not agree with the CGRT activity. This result suggests that the difference in CGRT among varieties occurred post-transcriptionally. Nucleotide variation in LcFGRT4 was surveyed by sequencing 30 litchi accessions with different anthocyanin profiles. Eight non-synonymous single-nucleotide polymorphisms were detected. Type A LcFGRT4 sequence (LcFGRT4A) was observed in cyanidin-3-glucoside-dominant varieties, whereas type B LcFGRT4 sequence (LcFGRT4B) was detected in cyanidin-3-glucoside-dominant varieties. A mutant in 343 C/G polymorphism was targeted as the critical point responsible for the CGRT activity. Results indicated that a single-point mutation in LcFGRT4 could alter the activity of CGRT and may contribute to the diverse anthocyanin profile of litchi. [ABSTRACT FROM AUTHOR]