Abstract
High
temperature (HT) stress induces male sterility, leading to yield reductions in
crops. DNA methylation regulates a range of processes involved in plant
development and stress responses, but its role in male sterility under HT
remains unknown. Here, we investigated DNA methylation levels in cotton
(Gossypium hirsutum) anthers under HT and normal temperature (NT) conditions by
performing whole-genome bisulfite sequencing to investigate the regulatory
roles of DNA methylation in male fertility under HT. Global disruption of DNA
methylation, especially CHH methylation (where H=A, C or T), was detected in an
HT-sensitive line. Changes in the levels of 24-nucleotide small-interfering
RNAs were significantly associated with DNA methylation levels. Experimental
suppression of DNA methylation led to pollen sterility in the HT-sensitive line
under NT conditions but did not affect the normal dehiscence of anther walls.
Further transcriptome analysis showed that the expression of genes in sugar and
reactive oxygen species (ROS) metabolic pathways were significantly modulated
in anthers under HT, but auxin biosynthesis and signaling pathways were only
slightly altered, indicating that HT disturbs sugar and ROS metabolism via
disrupting DNA methylation, leading to microspore sterility. This study opens
up a pathway for creating HT-tolerant cultivars using epigenetic techniques.