Genome-wide transcriptomic responses to heat stress in maize

High temperature has large impacts on growth and yield in crops, but the underlying molecular mechanism is not well understood. We investigated the effects of heat stress on the mRNA and small RNA transcriptomes in various tissues and developmental stages of maize plants. We discovered a plastid-derived 19-nucleotide (nt) small RNA, presumably the footprint of a pentatricopeptide repeat (PPR) protein, being significantly induced by heat stress, suggesting that heat stress induces the turnover of certain plastid transcripts. Consistently, nuclear genes responsible for photosynthesis in chloroplasts were repressed after heat stress. On the contrary, the abundance of 24-nt siRNAs from transposable elements was conspicuously reduced by heat stress in tassels and roots, and nearby genes showed a similar expression trend. Finally, we identified some microRNAs (miRNAs) that have never been reported in other plant species to be responsive to heat stress, in particular some miRNA*s. This study generated an atlas of transcriptomic responses to heat stress in maize.