Studies On The Mechanism Of Thermosensitive Genic Male Sterility Of Wheat Line BS366

The male sterility of wheat thermosensitive genic male sterile (TGMS) line BS366 is strictly controlled by temperature. When a TGMS line BS366 is exposed to an appropriate low temperature, starting at the PMC stage and continuing to the meiosis stage, TGMS lines BS366 exhibit indehiscent anthers and lack pollen grains, while other organs, including pistils, and seedlings develop normally. This suggests that microsporogenesis is much more sensitive to cold stress compared with female reproductive development and vegetative growth.Our objective is to elucidate how cold stress influences the microsporogenesis process of TGMS lines BS366. As a first step towards achieving this aim, the histological features were examined in TGMS-line anthers. During cold stress, abnormal separation of dyads occurred during male meiosis I, owing to failure of male meiotic cytokinesis. The fluorescence labeling and transmission electron microscopy results further revealed that the phragmoplast structure was defectively formed and the cell plate was abnormally assembled during meiosis I under cold stress. To gain further insight into the developmental transition throughout microsporogenesis underlying the histological changes, genomic transcriptional profiling of TMGS-line anthers over a developmental time-series was monitored under cold stress and in controls. A total of 840 annotated probe sets showed significant changes in transcript levels under cold treatment, but 278 of these common cold-responsive genes were eliminated by comparisons with the cold-treated Jing411 controls. Comparing the transcriptomes of cold-stressed lines and the controls, signaling systems that orchestrated, cytoskeleton activity were moderately induced in response to cold-stress in anthers of the TGMS line; however, genes involved in dynamic organization of the cytoskeleton were dramatically repressed. Forthermore, microRNA (miRNA) plays an important role in plant development and response to bio-or abio-stress. Exploring the role of miRNA in the anther developmental context to respond to cold stress will help to understand the mechanism of male sterility. Total 80 miRNAs have been identified by small RNA sequencing with next-generation sequencing technology. A transcriptome-wide experimental method, called "degradome sequencing", was used to directly detect cleaved miRNA targets. The expression profiles of miRNAs and their targets indicated that tasiRNA-ARF and miR167 family were significantly depressed by cold stress, however, the ARF target genes were abnormally induced at meiosis stage in TGMS line. These results suggest the concerning relationship between abnormal regulation of miRNAs under cold stress and male sterility of TGMS line.