Enhanced Reproductive Thermotolerance of the Tomato high pigment 2 Mutant Is Associated With Increased Accumulation of Flavonols in Pollen.

Nicholas Rutley,Jeffrey F Harper,Michal Lieberman-Lazarovich,Gad Miller,Golan Miller,Fengde Wang

doi:10.3389/fpls.2021.672368

Nicholas Rutley, Jeffrey F Harper + Show 4 more

Open Access

https://doi.org/10.3389/fpls.2021.672368

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Abstract

Climate change has created an environment where heat stress conditions are becoming more frequent as temperatures continue to raise in crop production areas around the world. This situation leads to decreased crop production due to plant sensitivity to heat stress. Reproductive success is critically dependent on plants’ ability to produce functional pollen grains, which are the most thermo-sensitive tissue. Flavonols are plant secondary metabolites known for their potent antioxidative activity, essential for male fertility in several species including tomato, and implicated in heat stress tolerance. Since flavonols are highly abundant in fruits of the tomato high pigment 2 (hp2) mutant, we tested the level of flavonols in pollen of this mutant, under the hypothesis that increased accumulation of flavonols would render pollen more tolerant to heat stress. Indeed, pollen from two alleles of the hp2 mutant was found to have flavonols levels increased by 18 and 280% compared with wild-type (WT) under moderate chronic heat stress (MCHS) conditions. This mutant produced on average 7.8-fold higher levels of viable pollen and displayed better germination competence under heat stress conditions. The percentage of fully seeded fruits and the number of seeds per fruit were maintained in the mutant under heat stress conditions while decreased in wild-type plants. Our results strongly suggest that increased concentrations of pollen flavonols enhance pollen thermotolerance and reproductive success under heat stress conditions. Thus, the high flavonols trait may help frame the model for improving crop resilience to heat stress.

Highlights

Crop productivity is often dependent on efficient sexual reproduction, a complex process that is very sensitive to environmental stresses, in particular heat stress, leading to considerable yield losses
Our findings indicate that the hp2 tomato mutant is more tolerant than wild-type plants to conditions of moderate chronic heat stress (MCHS)
Focusing on the male gametophyte for its known hyper-heat stress sensitivity, we found that under MCHS conditions, the hp2 lines maintained a bigger fraction of viable pollen, with increased metabolic activity (Figure 2)

Summary

Introduction

Crop productivity is often dependent on efficient sexual reproduction, a complex process that is very sensitive to environmental stresses, in particular heat stress, leading to considerable yield losses. Sensitivity to heat stress during the reproductive phase of plant development was documented in various crop species, and it was shown to be manifested by morphological. Tomato Pollen Flavonols Support Thermotolerance alterations of anthers, style elongation, bud abscission and reduced fruit number, weight, and seed set. In tomato (Solanum lycopersicum), a prolonged stress of day temperatures exceeding 32°C with night temperature above 20°C caused reduced fruit set, fruit weight, total yield, and seed production (El Ahmadi and Stevens, 1979; Peet et al, 1998). A comprehensive understanding of how plants respond to heat stress conditions to mitigate possible damage is fundamental for designing measures to sustain adequate productivity under increasingly warming climate

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