High-temperature induction of male sterility during barley (Hordeum vulgare L.) anther development is mediated by transcriptional inhibition

High-temperature induction of male sterility during floral organogenesis is a critical problem for barley (Hordeum vulgare L.) crops that the molecular basis is incompletely understood. Gene expression and differentiation of anthers were examined under normal (20 degrees C day/15 degrees C night) and elevated (30 degrees C day/25 degrees C night) temperatures. Serial analysis of gene expression analysis displayed contrasting profiles of gene expression in early panicles between control and high-temperature conditions. Several transcripts dramatically upregulated before development and differentiation of anther wall layers in normal temperatures, including histone H3, H4 and glycine-rich RNA-binding protein genes, were not upregulated at elevated temperatures and typically abundant mRNAs, such as 60S ribosomal protein L27a and glyoxalase I, appeared to be downregulated. Instead, development and differentiation of tapetum cells and pollen mother cells were completely aborted. Failure of transcriptional reactivation with return to normal temperatures increases with duration of elevated temperatures and is strongly correlated with observation of male sterility. Hyper-phosphorylation of the ser-5 residue of the C-terminal domain of the largest subunit of RNA polymerase II (RPB1) was noted to occur under high-temperature conditions. These results indicate that early development and differentiation of barley anthers are very sensitive to high-temperature stress causing major alterations in gene expression.