Item Details

title

HORMONAL AND ENVIRONMENTAL REGULATION OF REACTIVE OXYGEN SPECIES LOCALIZATION AND HOMEOSTASIS IN GUARD CELLS AND POLLEN

author

Postiglione, Anthony Earl

abstract

The rapid accumulation of reactive oxygen species (ROS) is a common response in plants cells to environmental cues such as drought and heat, two stresses that are increasing in prevalence as a result of climate change. Transient bursts of ROS can drive cellular signaling pathways, though signaling ROS must be tightly regulated to avoid accumulation to levels that initiate oxidative damage. This thesis examined how redox systems influence stress resistance to adverse weather conditions such as drought and heat stress, in two cell types that are critical to plant response to these environmental stimuli, stomatal guard cells and pollen. To prevent excess water loss during drought exposure, plants rapidly synthesize the drought hormone abscisic acid (ABA) to close the stomatal pore. Accumulation of ROS in the guard cells that flank the stomata following ABA perception has been observed previously, though the types of ROS and the subcellular location these ROS accumulate were largely unexplored. We utilized ROS-responsive chemical indicators and ratiometric bioreporters to show that ABA drives accumulation of hydrogen peroxide (H2O2) in distinct subcellular locations, including mitochondria, chloroplasts, nuclei, and cytosol. Genetic and chemical manipulation of mitochondrial ROS accumulation was shown to alter ABA sensitivity in guard cells. This thesis also evaluated the negative effects of ROS overaccumulation during exposure to elevated temperatures in tomato pollen, a cell type with extreme temperature sensitivity. We evaluated whether temperature increases ROS accumulation, and whether flavonol antioxidants can enhance pollen heat tolerance through the maintenance ROS homeostasis. We utilized a flavonol deficient mutant as well as a complementation line, and a line with increased flavonol production to show that flavonols reduce heat-induced ROS accumulation to prevent heat impaired pollen performance. RNA-sequencing analysis revealed several heat-responsive genes and that pollen with altered levels of flavonol synthesis exhibit differential transcriptional profiles in response to elevated temperature. This dissertation delivered detailed insight into redox systems that govern stress response and provide potential avenues for the protection of crop yields from drought and temperature stress.

subject

Abscisic Acid

Flavonols

Guard Cells

Pollen

Reactive Oxygen Species

Stress

contributor

Muday, Gloria K (advisor)

Brown-Harding, Heather M (committee member)

Johnson, Erik C (committee member)

McDonald Esstman, Sarah M (committee member)

date

2023-09-08T08:35:21Z (accessioned)

2023 (issued)

degree

Biology (discipline)

embargo

2024-09-07 (terms)

2024-09-07 (liftdate)

identifier

http://hdl.handle.net/10339/102602 (uri)

language

en (iso)

publisher

Wake Forest University

type

Dissertation