González Gil, Anna (2019) HAG5, a MYST histone acetyltransferase, modulates plant growth, defence and drought responses. PhD thesis, University of Warwick.

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Abstract

Climate change, unstable environmental conditions, rapid increase in human population and scarcity of resources are creating food insecurity. Climate change affects pathogen spread and water availability, challenging crop production globally. This could be the cause of severe food shortage in developing countries. Indeed, plant diseases and water scarcity are the main causes of crop losses, annually exceeding $220 billion worldwide (FAO, 2018). A sustainable strategy to prevent such losses is to create plants with enhanced tolerance to biotic and abiotic stresses. Unfortunately, enhanced stress tolerance often comes with severe developmental penalties such as reduced growth and yield.

In this thesis, I have identified that the histone acetyltransferase HAG5 acts as a major regulatory hub controlling plant homeostasis in a manner that simultaneously regulates stress responses and growth. The Arabidopsis thaliana mutant of this enzyme (hag5) has enhanced leaf area, longer roots and increased resistance to bacterial pathogens. In addition, the mutant is more tolerant to drought and less sensitive to abscisic acid (ABA), a phytohormone known to regulate plant growth and stress responses. We explored the molecular mechanisms underlying HAG5 activity and discovered that this enzyme interacts with an ABA responsive transcription factor and positively regulates ABA signalling. Through transcriptomic analysis, we unveiled that HAG5 is responsible for the transcriptional regulation of genes involved in cellular detox processes through reactive oxygen species (ROS) scavenging. By modulating ROS accumulation at the transcriptional level, HAG5 can potentially regulate the timing of plant commitment to senescence upon stress. Hence, supressing HAG5 activity results in delayed senescence and increased drought recovery.

We exploited the high level of conservation of HAG5 across plant lineages in an effort to engineer high-performing plants with enhanced disease resistance and drought tolerance, yet minimal impact upon growth. Here we describe two main lines of research; gene editing of HAG5 using CRISPR technology in Brassica oleracea and developing chemical inhibitors of the enzyme for foliar applications. Altogether, these strategies hold the potential to minimise crop losses, improving performance and stress responses by targeting HAG5 activity in crop plants.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QK Botany Q Science > QP Physiology
Library of Congress Subject Headings (LCSH):	Growth (Plants) -- Climatic factors, Growth (Plants) -- Molecular aspects, Plants -- Effect of stress on -- Molecular aspects, Plant immunology, Plants -- Drought tolerance, Histones, Acetyltransferases
Official Date:	September 2019
Dates:	Date Event September 2019 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	School of Life Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Ntoukakis, Vardis ; Giménez-Ibáñez, Selena
Format of File:	pdf
Extent:	xviii, 242 leaves : illustrations
Language:	eng

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