Discovering the Genetic Timekeepers in Bioenergy Crops

The Science

To get more feedstock from grass crops, scientists sought to identify the genetic “timekeeper” that stops plant growth and starts plant flowering. They studied the genes that keep a grass growing, or prevent it from flowering, until it has undergone prolonged cold exposure. After screening for and identifying model grasses, the team identified a mutant that flowers rapidly without cold exposure. They then described and characterized the mutant’s missing gene. They named their newly discovered gene REPRESSOR OF VERNALIZATION1 (RVR1).

The Impact

Increasing plant growth could improve the economics of biomass as an energy source. However, once a plant starts flowering, it stops growing. This study furthers the molecular-level knowledge of the flowering regulatory network in the model grass Brachypodium distachyon. The results advance the potential to manipulate flowering time in bioenergy grass crops. Such control would increase biomass yield and subsequently U.S. energy independence.

Summary

The timing of flowering is a key trait for biomass yield. A requirement for vernalization, the process by which prolonged cold exposure provides the ability for grass to flower when given the correct signal (known as competence), is an important adaptation to temperate climates that ensures flowering does not occur before the onset of winter. In temperate grasses, vernalization results in the up-regulation of the gene VERNALIZATION1 (VRN1) to establish competence to flower; however, little is known about the mechanism underlying repression of VRN1 in the fall season, which is necessary to establish a vernalization requirement. Scientists at the Great Lakes Bioenergy Research Center reported that a plant-specific gene containing a bromo adjacent homology and transcriptional elongation factor S-II domain, named RVR1, represses VRN1 before vernalization in the model grass specie Brachypodium distachyon. Thus, RVR1plays a role in establishing a vernalization requirement in B. distachyon and is likely to play the same role in other vernalization-requiring grasses. Interestingly, RVR1 is a plant-specific gene that is conserved across the plant kingdom, and this study provides the first example of a role for this class of plant-specific genes.

Funding

This work was funded in part by the National Science Foundation (grant IOS-1258126), the U.S. Department of Energy (DOE) Great Lakes Bioenergy Research Center (DOE Office of Science, Biological and Environmental Research, DE-FC02-07ER64494), a National Institutes of Health-sponsored predoctoral training fellowship to the University of Wisconsin Genetics Training program, and the Gordon and Betty Moore Foundation and the Life Sciences Research Foundation for their postdoctoral fellowship, and Wallonie-Bruxelles International for their postdoctoral fellowships.

Publication

D.P. Woods, T.S. Ream, F. Bouche, J. Lee, N. Thrower, C. Wilkerson, and R.M. Amasino, “Establishment of a vernalization requirement in Brachypodium distachyon requires REPRESSOR OF VERNALIZATION1.” Proceedings of the National Academy of Sciences USA 114, 6623-6628(2017) [DOI: 10.1073/pnas.1700536114]