de novo Transcriptome Assembly and Differential Gene Expression Profiling of Anthocyanin Biosynthesis in Zoysiagrass (Zoysia japonica Steud.)

Zoysiagrass (Zoysia japonica Steud.) is commonly found in temperate climate regions and widely used for lawns. Red to purple pigments is accumulated in spike and stolon tissues of zoysiagrass cultivars, thereby decreasing the aesthetic value. Here we analyzed the anthocyanin contents of two zoysiagrass cultivars ‘Anyang-jungji’ (AJ) and ‘Greenzoa’ (GZ) that produce spikes and stolons with purple and green colors, respectively. HPLC analysis revealed that cyanidin and petunidin were primarily accumulated in the pigmented tissues. In parallel, we performed a de novo transcriptome assembly and identified differentially expressed genes between the two cultivars. We found that two anthocyanin biosynthesis genes encoding anthocyanidin synthase (ANS) and dihydroflavonol 4-reductase (DFR) were preferentially up-regulated in the purple AJ spikes. Both ANS and DFR genes were also highly expressed in other pigmented zoysiagrass cultivars, but their expression levels were significantly low in the non-pigmented cultivars. These findings strongly suggest that up-regulation of ANS and DFR is key factor for tissue-specific anthocyanin biosynthesis and differential pigmentation in zoysiagrass. The present study also demonstrates the feasibility of a de novo transcriptome analysis to identify the key genes associated with specific traits, even in the absence of reference genome information.