Transcriptome analysis of purple pigment formation in Colocasia esculenta

Taro(Colocasia esculenta(L.)Schott)is an important crop in Africa,Southeast Asia,and subtropics and is used as a food and medicine.The purple color pigmentation is an appealing character in taro.We sampled taro corms of the cultivar‘Lipu Taro’at four developmental stages,including LPYS1(without purple pigment,50 days of development(DOD)),LPYS2(very few purple pigments,75 DOD),LPYS3(moderate purple pigments,115 DOD)and LPYS4(high purple pigments,205 DOD).The purpose of our study was to identify the key genes underpinning the purple pigmentation in taro based on RNA-sequencing.Through RNA-Seq,6453 differentially expressed transcripts(DETs)were identified between purple and non-purple pigmented samples.We identified 41 and 12 flavonoid and anthocyanin related DETs transcripts,respectively.These DETs were upregulated at LPYS2,LPYS3,and LPYS4 as compared to LPYS1,indicating their positive contribution to the color formation in taro.Moreover,we identified several DETs encoding for transcription factors,including MYB and bHLH,known to be major regulators of structural genes involved in the flavonoid-anthocyanin pathway.Finally,we reported several plant hormones(ethylene,auxin,gibberellin,jasmonic acid,and cytokinin)related DETs,which are predicted to play important roles in the corm coloration.Different regulation of transcripts representing the flavonoid-anthocyanin biosynthesis pathway,plant hormone transduction pathway,and transcription factors may have key roles in purple pigmentation in taro.Our findings will facilitate future research on improving the quality and appeal of taro.