Histological and transcriptomic analyses of Tadukan-type cytoplasmic male sterile rice lacking anther dehiscence

Cytoplasmic male sterility (CMS) has been effectively used to produce F1 hybrid seeds, although the underlying molecular mechanism remains poorly understood. In this study, we performed histological and transcriptomic analyses to elucidate the molecular mechanism underlying TA-CMS rice (Oryza sativa) obtained from the cytoplasm of ｀Tadukan’ combined with the nucleus of ｀Taichung 65,’ which exhibits anther indehiscence phenotype owing to a mitochondrial genetic factor orf312. The surfaces of the pollen and anthers appeared normal, whereas the inner tissue lacked the intercellular cavity that is essential for the anther dehiscence. RNA sequencing analysis identified differentially expressed genes involved in the cell wall organization and the jasmonic acid signal transduction. Jasmonic acid and hydrogen peroxide accumulated normally, and exogenous treatments with them did not restore the anther dehiscence or seed setting in TA-CMS. Based on these findings, we suggest the following molecular hypothesis for TA-CMS: the loss of JA signaling-mediated reorganization of the cell wall results in the lack of cavity formation under the stomium, which is crucial for the anther dehiscence at the time of flowering.