Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Understanding Chilling Tolerance of Photosynthesis in the C4 Grass Miscanthus
Abstract
Miscanthus is a genus of the Poaceae family and utilizes NADP-ME subtype C4 photosynthesis. Miscanthus occupies a broad natural range, temperate to tropical, and populations exhibit local adaptation. C4 grasses are notoriously susceptible to chilling stress, but some Miscanthus species boast high tolerance. We utilized a primary set of three Miscanthus species derived from cold-temperate (M. sacchariflorus, highly tolerant), subtropical (M. sinensis, sensitive), and a hybrid of the two (M. xgiganteus, intermediately tolerant) to investigate chilling tolerance in this genus. The first approach demonstrates increased non-photochemical quenching (NPQ) in tolerant species during chilling and reveals the mechanism relies on quenching xanthophylls. We reveal that violaxanthin de-epoxidase (VDE), the enzyme responsible for inducing xanthophyll quenching, has less sensitivity to reducing environments when challenged with the reductant dithiothreitol (DTT) and an increased NPQ induction rate during initial light exposure. Ascorbate, a cofactor for VDE, is consumed more rapidly by tolerant species after 15 minutes of light exposure. We reveal that tolerant species maintain a pool of quenching xanthophylls through the night and increase this retention under chilling stress. The second chapter characterized metabolic changes in response to chilling stress both before dawn and after 10 or 15 minutes of light exposure in these species, revealing that tolerance relates to improved energy balance during stress, accumulation of osmolytes, and prevention or detoxification of ROS during light exposure. Shikimate pathway metabolites were found to differentially accumulate in these species regardless of treatment, suggesting tolerant species are pre-acclimated to endure chilling stress. Betaine and galactinol accumulate in tolerant species to stabilize photosynthetic membranes during abiotic stress. Chilling tolerant Miscanthus utilizes multiple strategies to tolerate chilling, both concerted and in response to chilling stress.Finally, I present our early work exploring the relationship between reduction-oxidation state of the quinone pool and transpiration water loss in transgenic Nicotiana tabacum (Tobacco) overexpressing VDE under water-limited greenhouse conditions. VDE-overexpressing tobacco plants reach higher levels of maximum NPQ, maintaining an oxidized quinone pool by dissipating more incident light than wildtype. The oxidized quinone pool signals to stomata to remain closed, improving water use efficiency.
Subject Area
Biogeochemistry|Plant sciences|Biochemistry|Physiology
Recommended Citation
Haupt, Jared L, "Understanding Chilling Tolerance of Photosynthesis in the C4 Grass Miscanthus" (2023). ETD collection for University of Nebraska-Lincoln. AAI30814338.
https://digitalcommons.unl.edu/dissertations/AAI30814338