Abrin inactivating mitochondrial ribosome induced anther abortion in cotton CMS line LD6A by damaging mitochondrial membrane structure

Cytoplasmic male sterile (CMS) system has extensively been exploited for hybrid vigor in plant breeding pro-grams. However, its application in many crops is limited due to poor understanding of molecular mechanism of fertility restoration. Using advanced analytical approaches, we aimed to elucidate the molecular pathways, regulating CMS induction and fertility restoration in cotton. Reproductive structures of a novel CMS (LD6A) and its maintainer (LD6B) lines were analyzed for physiological and proteomic changes during the development process. Transmission electron micrographs of anther tapetum showed a relatively indistinct inner ridge of CMS than of LD6B mitochondria at tetrad stage. Furthermore, at pollen mother cell and tetrad stages, CMS anthers accumulated a significantly higher reactive oxygen species than the maintainer line. At the protein level, CMS anthers induced significantly higher Abrin (XP_016705148.2), lower tricarboxylic acid cycle enzyme (malate dehydrogenase, malic enzyme, isocitrate dehydrogenase), and histone acetyltransferase expression than its maintainer line. Suggesting that abnormal sequence of mitochondrial ribosome gene rps4 and rpl10 and high expression of ribosome-inactivating protein Abrin in CMS line damaged mitochondrial membrane. This inhibited energy supply from the non-degraded tapetum, and consequently induced pollen sterility in LD6A. These data provide new insights into CMS mechanism in cotton crops that can be used for developing new CMS germplasm resources.

Automated summary

Using advanced analytical approaches, the molecular pathways regulating CMS induction and fertility restoration in cotton were elucidated. The study revealed that CMS anthers had a relatively indistinct inner ridge of mitochondria and accumulated significantly higher levels of reactive oxygen species than the maintainer line. At the protein level, CMS anthers showed higher expression of Abrin and lower expression of tricarboxylic acid cycle enzymes and histone acetyltransferase. These findings suggest that abnormal mitochondrial ribosome gene sequence and high expression of ribosome-inactivating protein Abrin damaged the mitochondrial membrane and inhibited energy supply, leading to pollen sterility in CMS line LD6A.