Fertility Characterization And Anther Proteomic Analysis Of A Novel Photosensitive Male Sterile Mutant In Cotton (Gossypium Hirsutum L.)

Cotton(Gossypium hirsutum L.) is one of most important commercial crops all over the world. Elite cotton variety with high yield and quality is the goal of every breeder. And, utilization of heterosis is a key strategy to achieve this goal. The F1 progeny of cotton performs strong heterosis in boll number, weight, and seed cotton yield. The hybrid seeds are widely produced in our country, especially in Yangtze River cotton-growing region, where hybrids have been the leading cultivars. However, the current cotton hybrid seeds are mainly produced through hand emasculation and pollination, which requires a large labor force and cost. It is urgent to explore a new hybrid breeding system. It has proven that using of photo- or thermo- sensitive male sterile(P/TGMS) lines as the female parent in the hybrid breeding system can greatly simplify the breeding procedure. A PGMS or TGMS line grown under restrictive conditions(long-day or high temperature conditions) serves as the male-sterile female parent. This same line can be propagated under permissive conditions(short-day or low-temperature conditions). Therefore, a two-line system simplifies hybrid seed production and reduces costs. Recently, the production of two-line hybrid rice and oilseed based on PGMS or TGMS has been widely used. CCRI9106, a novel PGMS cotton mutant(MT) with a virescent marker, was isolated from CCRI040029(WT) by space mutation breeding technology, and appeared to be male sterile under long-day conditions and fertile under short-day conditions. It is of great significance to study the way to use CCRI9106 and it male sterility mechanism.1. In this study, we first recorded the pollen fertility of CCRI9106 in detail when grown in Anyang. It flowered in late July, and was male sterile. So, it is in low risk to produce hybrid seeds. On the other hand, 200 seeds per plants would be harvest when CCRI9106 was grown in Sanya. These results suggested that it is possible to apply a two-line hybrid breeding system with CCRI9106 in cotton.2. CCRI9106 was crossed with 20 male parents to evaluate the heterosis. The F1 progenies from Yu-13 and 302355 were high in yield, which exceeded Lu-28 for 21% and 14%, respectively. The F1 progenies from CCRI425, CCRI69 and Rihui-6 were good in quality. Therefore, CCRI9106 has a great value in heterosis.3. To gain detailed insights into the cellular defects occurring in CCRI9106 anther, cross sections were further examined. The pollen development process was divided into three main stages according to bud length: stage 1, the meiosis stage,(from floral bud differentiation to formation of tetrads, floral bud length ≤ 5 mm), stage 2, the tapetum was gradually degraded to support microspore maturation(from the release of microspores to microspores maturation, 5 mm ≤ floral bud length ≤ 10 mm), and stage 3, pollen maturation,(from pollen maturation to the release of mature pollen, floral bud length ≥ 11 mm). In CCRI9106 plants, no difference was observed at stage 1, but male sterility was initiated at early stage 2 and settled at early stage 3.4. Two-dimensional electrophoresis and i TRAQ-facilitated proteomic analyses were performed to explore the male sterility mechanism and, 56 and 365 differential expressed proteins were identified, respectively. They were involved in energy and metabolic pathey, exine formation, protein degradation, pollen germination, and etc.5. Based on the proteins function and histological results, we draw a simple model of male sterility in CCRI9106. Microspore mother cells underwent meiosis normaly, forming tetrads. Then, abnormal tapetum degradation occurred, which may result from unbalance of Ca2+ homeostasis. This change reduced the sporopollenin synthesis and defective pollen exine formed. Disordered proteins expression in energy and metabolic pathways suggested insufficient energy supplying for microspore maturation. Furthermore, active proteasome promoted degradation of functional proteins. As a consequence, the pollen failed in accumulation of pollen components for pollen tube growth. Finally, nonviable pollen grains were formed, and male sterility was observed in CCRI9106.