Dissertation

Brachypodium sylvaticum: Developing a New Model to Study Freezing Tolerance in Temperate Perennial Grasses

Lambert-Rivest, Gabriel

2019

Overview

In the current agricultural context, sustainable crops such as perennial grains have the potential to further secure the world's demand in cereals. Under northern climates, perennial grains are as vulnerable as annual grains to early and late frost events that cause important damages and economic losses. Therefore, the understanding of cold-acclimation in perennials grasses, that is the process by which temperate plants prime their defence against freezing stress, is necessary to cultivate them at their full potential under northern latitudes. Here, we tested the newly developed perennial grasses model B. sylvaticum in its capacity to facilitate the study of cold-acclimation and freezing tolerance in perennial grasses. Accordingly, our hypothesis is that B. sylvaticum can cold-acclimate in response to low temperatures and increase its freezing tolerance level, and that a phenotypic range in the capacity to cold-acclimate will be observed across different accessions. To verify this, we first determined the survival of non-acclimated and cold-acclimated live plants to freezing stress. We observed an increase of 2 °C in the freezing tolerance of cold-acclimated plants in nine tested accessions, themselves differentiated by a diversity in cold-acclimation capacity. This was followed by the determination of cold-responsive genes transcript accumulation profiles in B. sylvaticum. Consequently, we determined that three cold-responsive genes BsCOR413, BsCOR410 and BsCBF2.1 were differentially regulated in response to cold in nine accessions of B. sylvaticum, which indicates that this plant most likely possesses the molecular mechanisms that allow cold-acclimation and the subsequent increase in its freezing tolerance. In addition, we tested a high-efficiency transformation protocol for B. sylvaticum under our laboratory conditions. We report the transformation of a B. sylvaticum plant that overexpresses by thirtyfold the acetyltransferase GCN5, an epigenetic modifier that was previously linked to cold response in plants. Therefore, B. sylvaticum's capacity to cold-acclimate through the observed underlying molecular mechanisms as well as its ability to be transformed under laboratory conditions highlights its potential in being used as a model to study cold response in perennial grasses. Findings made in B. sylvaticum could thus be transferred and applied to economically important perennial grains crop in order to increase their freezing tolerance.

• Publisher: ProQuest Dissertations & Theses
• Subject: Plant sciences
• ISBN: 9798698520740