Studies On Mechanism Of The Restorability Improvement Of Transgenic GST Restorer For CMS-based Hybrid Cotton

There are significant heterosis in cotton, and planting hybrid cotton can produce higher yield and better fiber quality. At present, hybrid cotton seeds are produced mostly by hand-emasculation and pollination, resulting in a high cost and low efficiency of production, which embarrasses the heterosis use of hybrid cotton. Cytoplasmic male sterile plants can't produce functional male gametophytes but can produce functional female gametophytes. If insects, such as bees, are employed to pollinate cotton pollens from restorer to the sterile plants in the field of hybrid seed production, it is more effective and economic. In 1973, Meyer reported that a cytoplasmic male sterile system in cotton was developed by combining the nuclear of G. hirsutum L. with the cytoplasm of G. harknessii Brandegee. However, this system had not been widely used because of weak restorability in its restorer 'DES-HAF277' to cytoplasmic male sterility. 'Zheda strong restorer', a transgenic restorer, was developed by transferring glutathione S-transferase (GST) gene parB (GeneBank Accession: D10524) into a restorer 'DES-HAF277' by Wang xuede, and overcame the defect of weak restorability to cytoplasmic male sterility in recipient restorer. When compared with recipient restorer 'DES-HAF277', the fertility restorability of 'Zheda strong restorer' to male sterility was been enhanced by 25.8% in the percentage of viable pollens of hybrid (Fj). So 'Zheda strong restorer' had a high value in hybrid cotton production, but the mechanism about restorability increase of 'Zheda strong restorer' was not clear.For this reason, a cytoplasmic male sterile line and its maintainer were used as checks, and hybrid (F,) restored by 'Zheda strong restorer' and hybrid (F,) restored by 'DES-HAF277' were used as materials in this article to study on mechanism of restorability improvement of transgenic GST restorer for CMS based hybrid cotton. Field experiments were done to study the effects of exogenous GST gene on performance of hybrid (F)) yield and fiber quality. The microstructural and ultrastructural observations were conducted to study the effects of exogenous GST gene on the cytological structure of hybrid (F]) anther. Biochemical analysis was done to study effects of exogenous GST gene on metabolism of respiration and reactive oxygen species (ROS) in hybrid (Fi) anther and its mitochondria. Finally, transcription characteristics of exogenous GST gene in hybrid (F]) were studied by real-time quantitative RT-PCR. The main results were:The productive rates of ROS in CMS anther and its mitochondria were respectively distinctly higher than that in fertile anther and its mitochondria, and so high that ROS scavenging system in cells was impaired, resulting ROS accumulation and male cell degeneration. It was reflected that anther cytological phenotypes were significantly abnormal: firstly, male cell mitochondria of CMS line were swelling, cristae disappearing, matrix diffusing and membrane rupturing at the sporogenous cell division stage. Then, male cells became shrinked, membrane aparted and ribosome density declined. As the number of abnormal mitochondria was increased, male cells showed rupturation, vacuolation, chromatin condensation and endoplasmic reticulum expandation.