Non Technical Summary
Plant reproduction is highly sensitive to changing environmental conditions, with deviations from optimal temperature having profound negative effects on multiple aspects of reproduction. Plants reproduce through a precise developmental process which yields fruits and seeds that are the central products of agriculture. Short- and long-term increases in temperature during plant reproduction prevent successful fertilization, resulting in impaired seed and fruit production that can lead to devastating crop losses. In particular, the development, germination, and tube growth of pollen are essential for plant fertilization, but all of these processes are extremely sensitive to high temperature stress. Our team has examined the detrimental effects of elevated temperature on reproductive success of tomato, an important agricultural species, and have begun to uncover signals induced by high temperature that lead to negative impacts on pollen function. We have found that tomato pollen tubes transiently exposed to elevated temperature have increased levels of reactive oxygen species, a group of reactive chemicals that can damage cellular molecules. We have also uncovered a role for flavonols - antioxidant compounds produced by plants - in protecting pollen from high temperature stress. The goal of this project is to better understand how elevated temperature increases reactive oxygen species in pollen and how plants can protect themselves from these reactive and damaging molecules by synthesis of antioxidants. A goal is to apply this knowledge to breeding or gene editing to yield tomato plants better adapted to increases in temperature linked to global climate change.?
Animal Health Component
Research Effort Categories
Goals / Objectives
Plant reproduction is impaired at elevated temperatures, reducing seed and fruit production and leading to devastating crop losses. High temperature stress elevates reactive oxygen species (ROS) to damaging levels in pollen. Little is known about how this temperature-induced ROS is synthesized and how thermotolerant Solanum lycopersicum (tomato) cultivars maintain pollen viability and tube growth. We have found that a tomato mutant with impaired flavonol antioxidant synthesis has elevated ROS and pollen grains and tubes that are hypersensitive to high temperature, while a plant transformed with a transgene leading to overproduction of flavonols is thermotolerant. Thermotolerant cultivars have pollen tube growth and ROS levels that do not change at elevated temperatures. These findings suggest plant defense against high temperature includes synthesis of specialized, antioxidant metabolites that maintain ROS homeostasis.This project will identify the mechanisms by which pollen of thermosensitive varieties have elevated temperature-induced ROS and why thermotolerant cultivars maintain their ROS homeostasis. We will test the hypothesis that pollen of these thermotolerant cultivars have reproductive success at high temperature due to reduced ROS biosynthesis and/or elevated synthesis of flavonols and other antioxidant systems. We will apply the gained knowledge to engineer plants with enhanced thermotolerance, using flavonol antioxidants as a target to be overproduced and the heat-induced ROS synthesizing machinery as targets for deletion in a heat stress- and pollen-specific manner. The proposed experiments will provide insights into the role of ROS homeostasis in tomato reproduction under adverse climate conditions with the goal of engineering plants to produce thermotolerant pollen. This project will explore the mechanisms by which the balance between ROS levels and their mitigation by flavonols (and other antioxidant metabolites and proteins) modulate pollen function at high temperatures in thermosensitive and thermotolerant cultivars. The planned experiments will provide insights into the role of ROS and antioxidants in plant reproduction under adverse climate conditions with the goal of engineering thermotolerant tomato pollen using heat-stress induced and pollen targeted approaches.This project has 3 specific aims:Aim 1: Identify spatiotemporal ROS accumulation in pollen during heat stress and define the biosynthetic machinery that controls high temperature-induced ROS synthesis.Aim 2: Determine if elevated temperature induces biosynthesis of flavonols and/or other antioxidants to maintain ROS homeostasis in tomato pollenAim 3: Perform precision metabolic engineering to improve reproductive thermotolerance in tomato by increasing flavonols in male reproductive structures
This project will employ a range of experimental approaches to both identify the role of reactive oxygen species (ROS) in high temperature stress and the mechanisms that minimize ROS to protect pollen of thermotolerant plants from this stress, but also will apply this knowledge to breed and engineer plants to withstand this stress. To understand the impact of elevated temperature, we will use a variety of methods to image changes in ROS and pollen growth and development as a result of short- and long-term temperature stress. We will use biochemical and molecular biological methods to quantify the levels of ROS generating and ROS scavenging enzymes and the transcripts that encode them, respectively. We will manipulate levels of ROS both through chemical treatments and by knocking out or over expressing gene products predicted to control levels of ROS and antioxidants. Finally, we will use precision metabolic engineering to target synthesis of molecules that minimize ROS accumulation in pollen with the goal of generating new thermotolerant varieties.