Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2018-2019)

Background : Our research program is focused on discovery and characterization of molecular factors that control important traits in Canadian crops. In the proposed research, we focus on microRNA156 (miR156) , which affects a number of traits in plants. MiR156 functions by silencing genes that encode transcription factors from the SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) family. SPLs in turn regulate other downstream genes (target genes) that contain a specific SPL binding cis acting element. Thus, the propensity of miR156 to affect multiple plant traits could be attributed to its ability to regulate a large network of downstream genes. In Medicago sativa (alfalfa), miR156 affects traits such as forage yield and quality, plant architecture, flowering time, root development, nodulation, and drought tolerance by silencing at least seven SPL genes.

Objectives and methods : We propose to expand this research by investigating the molecular basis for the role that miR156 plays in abiotic stress tolerance in alfalfa. Specifically, we will characterize the seven miR156-targeted SPL genes to associate them to one or a small number of traits normally affected by miR156 in alfalfa. We will also identify SPL-regulated downstream genes to generate knowledge about the components of the miR156-SPL genetic network, ascribe functions to at least some of the SPL genes and their target genes in alfalfa, and thus generate knowledge and molecular markers that could be used in crop improvement. Our objectives are:
1. To characterize the role of miR156 in abiotic stress, with emphasis on drought, salinity, heat, and aluminum stress.
2. To generate over-expression and knockdown alfalfa plants for each of the miR156-targeted SPL genes in order to study their functions in relation to miR156 -induced stress tolerance in alfalfa.
3. To test alfalfa plants with altered expression of each of the SPL genes at the morphological and physiological levels for effects on traits such as biomass yield, root morphology, flowering time, and tolerance to abiotic stress. Results of these experiments will link each SPL to one or a small number of traits elicited by miR156 .
4. To uncover and characterize downstream SPL-regulated genes involved in abiotic stress tolerance. These genes would be ideal markers for alfalfa improvement.

Novelty and expected significance of the work: The new knowledge to be generated from this research will enhance our understanding of the miR156-SPL gene regulatory network in alfalfa, and potentially other plants. The findings could be further exploited in either basic research to understand the molecular basis for various alfalfa traits, or used in applied research to improve alfalfa traits for livestock feed, and potentially for cellulosic biofuel applications. Some of the knowledge may also be transferable to other major crops to improve their yield and agronomic performance.