GbMYBR1fromGinkgo bilobarepresses phenylpropanoid biosynthesis and trichome development inArabidopsis

Main Conclusion GbMYBR1, a new type of R2R3-MYB repressor fromGinkgo biloba, displayed pleiotropic effects on plant growth, phenylpropanoid accumulation, by regulating multiple related genes at different levels. Ginkgo bilobais a typical gymnosperm that has been thriving on earth for millions of years. MYB transcription factors (TFs) play important roles in diverse processes in plants. However, the role of MYBs remains largely unknown inGinkgo. Here, an MYB TF gene fromGinkgo, designated asGbMYBR1, was found to act as a repressor in multiple processes.GbMYBR1was mainly expressed in the leaves ofGinkgo.Over-expression ofGbMYBR1inArabidopsis thalianaled to growth retardation, decreases in lignin content, reduced trichome density, and remarkable reduction in anthocyanin and flavonol contents in leaves.Proanthocyanidin content was decreased in the seeds of transgenicArabidopsis, which led to light-brown seed color. Both qPCR and transcriptome sequencing analyses demonstrated that the transcript levels of multiple genes related to phenylpropanoid biosynthesis, trichome formation, and pathogen resistance were down-regulated in the transgenicArabidopsis.In particular, we found that GbMYBR1 directly interacts with the bHLH cofactor GL3 as revealed by yeast two-hybrid assays. Our work indicated thatGbMYBR1has pleiotropic effects on plant growth, phenylpropanoid accumulation, and trichome development, mediated by interaction with GL3 or direct suppression of key pathway genes. Thus,GbMYBR1represents a novel type of R2R3 MYB repressor.