Expression Patterns of Three UGT Genes in Different Chemotype Safflower Lines and under MeJA Stimulus Revealed Their Potential Role in Flavonoid Biosynthesis

<div><p>Safflower (<i>Carthamus tinctorius</i> L.) has received a significant amount of attention as a medicinal plant in China. Flavonoids are the dominant active medical compounds. UDP-glycosyltransferase plays an essential role in the biosynthesis and storage of flavonoids in safflower. In this study, 45 UGT unigenes were screened from our transcriptomic database of safflower. Among them, 27 UGT unigenes were predicted to own a complete open reading frame with various pI and Mw. The phylogenetic tree showed that <i>Ct</i>UGT3 and <i>Ct</i>UGT16 were classified under the UGT71 subfamily involved in metabolite process, whereas <i>Ct</i>UGT25 has high identities with <i>Po</i>UGT both catalyzing the glycosylation of flavonoids and belonging to the UGT90 subfamily. cDNA microarray exhibited that the three UGT genes displayed temporal difference in two chemotype safflower lines. To functionally characterize UGT in safflower, <i>Ct</i>UGT3, <i>Ct</i>UGT16 and <i>Ct</i>UGT25 were cloned and analyzed. Subcellular localization suggested that the three UGTs might be located in the cell cytoplasm and chloroplast. The expression pattern showed that the three UGTs were all suppressed in two lines responsive to methyl jasmonate induction. The co-expression relation of expression pattern and metabolite accumulation demonstrated that <i>Ct</i>UGT3 and <i>Ct</i>UGT25 were positively related to kaempferol-3-<i>O</i>-β-D-glucoside and <i>Ct</i>UGT16 was positively related to quercetin-3-<i>O</i>-β-D-glucoside in yellow line, whereas <i>Ct</i>UGT3 and <i>Ct</i>UGT25 were positively related to quercetin-3-<i>O</i>-β-D-glucoside in white line. This study indicates that the three <i>Ct</i>UGTs play a significant and multiple role in flavonoids biosynthesis with presenting different functional characterization in two safflower lines.</p>