Transcriptome Sequencing To Identify Novel Transcription Factors Involved In Condensed Tannin Production In Clover

White clover (Trifolium repens L.) is the dominant legume in temperate pasture systems, where it provides high quality feed for grazing ruminants. White clover synthesises both anthocyanins and condensed tannins (CT), but levels are negligible in leaf tissue.  CT are particularly important in pastoral systems for improved animal health and production. Anthocyanins and CT share common biosynthetic steps of the phenylpropanoid pathway, and their production is regulated by a complex group of transcription factors.

We recently augmented CT accumulation in white clover leaves, by the over-expression of TaMYB14 (a MYB transcription factor from T. arvense).  Here, we assessed impacts of TaMYB14 over-expression on the white clover leaf transcriptome. Using the Illumina HiSeq2000 platform, we obtained leaf transcriptomes from four clover genotypes exhibiting different anthocyanin and CT phenotypes: a white clover cultivar; a high anthocyanin line; T. arvense, which naturally synthesises leaf CT; and a transgenic white clover line, which accumulates high levels of CT due to over expression of TaMYB14.

Transcripts from leaves were sequenced using the Illumina HiSeq2000 platform, generating approximately 207 million reads, assembled into 430,000 contigs.  The four transcriptome pools were compared, allowing the identification of numerous genes involved in the biosynthesis and regulation of phenylpropanoid compounds, including candidate transcription factors putatively involved in CT regulation. This transcriptome set provides a valuable tool to further elucidate the interplay between secondary compound pathways and suggests a complex CT/ anthocyanin regulation system exists in clover, comparable to that reported for grape and poplar.