Abstract
Sexual reproduction is a critical process in the life-cycle of plants and very sensitive to environmental perturbations. To better understand the effect of high temperature on plant reproduction, we cultivated tomato (Solanum lycopersicum) plants in continuous mild heat. Under this condition we observed a simultaneous reduction in pollen viability and appearance of anthers with pistil-like structures, while in a more thermotolerant genotype, both traits were improved. Ectopic expression of two pistil-specific genes, TRANSMITTING TISSUE SPECIFIC and TOMATO AGAMOUS LIKE11, in the anthers confirmed that the anthers had gained partial pistil identity. Concomitantly, expression of the B-class genes TOMATO APETALA3, TOMATO MADS BOX GENE6 (TM6) and LePISTILLATA was reduced in anthers under continuous mild heat. Plants in which TM6 was partially silenced reacted hypersensitively to temperature elevation with regard to the frequency of pistilloid anthers, pollen viability and pollen quantity. Taken together, these results suggest that high-temperature-induced down-regulation of tomato B-class genes contributes to anther deformations and reduced male fertility. Improving our understanding of how temperature perturbs the molecular mechanisms of anther and pollen development will be important in the view of maintaining agricultural output under current climate changes.
Highlights
Sexual reproduction is a key process in the life-cycle of plants, both in natural and in agricultural settings, with fitness and yield, respectively, depending directly on its success
As has been reported before [31], tomato pollen viability was compromised when plants were grown under contiunuous mild heat (CMH), with clear effects being visible at ~32 ̊C/26 ̊C day- and night-time temperatures (CMH32; Fig 1A)
We observed that under these conditions part of the anthers developed deformations, consisting of spacing between anthers, twisting and greening of the tips (“antheridial cone splitting”; Fig 1B). The frequency of these deformations increased with higher temperatures (CMH34), while at the same time pollen viability was further reduced (Fig 1A)
Summary
The aim of this study was to identify the molecular changes underlying these deformations and determine the relation between anther deformation and impaired development of the male gametophyte under mildly elevated temperatures
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