1:00 pm - 2:00 pm
Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Madeline Lehmann. This seminar will be held via Zoom.
Thesis Topic: Down-regulation and mutation of pectin biosynthesis and flowering time genes as a possible means of enhancing biomass yield and digestibility in alfalfa (Medicago sativa)
Zoom link: https://ualberta-ca.zoom.us/j/94325917245?pwd=GoSAk2IIWUagINdSdeVnEkYW8IPTTG.1
Seminar Abstract:
Alfalfa (Medicago sativa) is the most widely cultivated perennial forage legume in the world. Its great economic importance in the beef and dairy industries is owed to its many favourable traits, including relatively high quality and yield, and symbiotic nitrogen-fixing capabilities. However, the projected increase in global demand for beef and dairy products and the loss of arable land to urbanization necessitate further improvement to productivity. Moreover, the inefficient conversion of plant biomass into animal products during rumen fermentation results in both economic losses and negative environmental impacts. Thus, digestibility provides another important trait for enhancement in this species.
Several strategies have been proposed for the simultaneous improvement of biomass yield and/or digestibility. One such strategy is the down-regulation or mutation of flowering time genes, such as SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), which has been previously demonstrated to delay flowering, resulting in improvements to vegetative biomass production and digestibility in several plant species. Another is the down-regulation or mutation of the pectin biosynthesis gene GALACTURONOSYLTRANSFERASE 4 (GAUT4), which has been previously demonstrated to improve both dry matter yields and extractability of cell wall sugars in plant species grown for bioethanol production.
As such, the overall aim of this study was to determine the effects of down-regulating or mutating these genes in alfalfa. RNA interference (RNAi) vectors were designed, generated, and transformed into alfalfa via Agrobacterium-mediated transformation in order to individually down-regulate the expression of MsSOC1a and MsGAUT4a. These RNAi genotypes were then evaluated for changes to morphological characteristics, as well as carbohydrate composition and drought tolerance in the case of MsGAUT4a, as a means of evaluating the potential of these genes as candidates for future improvement of alfalfa. CRISPR/Cas9 mutants of MsSOC1a and MsGAUT4a were also generated as a source of germplasm for future study and development.
The RNAi-mediated down-regulation of MsSOC1a resulted in delayed flowering, reduced biomass, and altered stem architecture, while the down-regulation of MsGAUT4a resulted in reduced galacturonic acid, increased nitrogen content and in vitro ruminal gas production, and increased sensitivity to drought stress. Future evaluation of the CRISPR/Cas9-mediated MsSOC1 and MsGAUT4a mutants generated in this study is warranted for further elucidation of the precise functions of these genes in alfalfa, as well as their viability as target genes for further improvement of agronomic traits in alfalfa. If successful, these genes could serve as targets for future molecular breeding of alfalfa to improve both our ability to meet the rising demand for ruminant products, as well as the environmental sustainability of livestock production.
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