(200-38) A genetic approach demonstrates that flavonols protect pollen from heat-increased reactive oxygen species that impair tomato pollen performance
Professor of Biology Wake Forest University Winston Salem, North Carolina
Body of Abstract: Plant reproduction is negatively impacted by elevated temperatures, which can ultimately result in reduced crop yields. Heat stress increases the accumulation of reactive oxygen species (ROS) in pollen, which reduces pollen viability, pollen tube germination, and fertilization. Plants can prevent ROS from reaching these damaging levels through synthesis of antioxidants, including flavonol metabolites. The tomato mutant, anthocyanin reduced (are), which has a defect in the gene encoding flavonol 3-hydroxylase (F3H) and reduced synthesis of flavonols, has impaired pollen function under optimal conditions, and is hypersensitive to heat stress. The are mutant has impaired pollen germination and pollen tube elongation in vitro and in vivo, marked by increased frequency of rupture and increased accumulation of ROS, which are all accentuated at elevated temperatures. Chemical complementation with flavonols and genetic complementation with an F3H transgene reversed the detrimental effects of elevated temperature on pollen germination and pollen tube rupture in are. Overexpression of F3H mitigated the temperature-induced ROS accumulation within pollen, conveying thermotolerance to this tissue. Consistent with plants modulating flavonol synthesis as a protective mechanism in response to elevated temperature, heat stress increased flavonols in pollen. We have performed RNA Seq in are, its parental line VF36, and a F3H overexpression line at optimal and elevated temperatures revealing substantial temperature-dependent transcriptional changes during both pollen germination and pollen tube elongation in are. These differ from the transcriptional responses in the parental line and F3H overexpression line, consistent with an important role of flavonols in the modulation ROS-dependent transcriptional remodeling at elevated temperatures. These results demonstrated the protective capabilities of flavonols from heat-induced ROS and provide mechanisms for future development of approaches to safeguard plant reproduction from elevated temperatures associated with global climate change. (Supported by USDA NIFA 2019-05552 and NSF IOS 1939255).