The Relationship Between Relative Quantity Of Gene Expression Related To Cotton Fiber Development And Quality

Cotton is the most important natural fiber crop in the world, China is an important cotton-producing country with great amount of textile exporting, so cotton plays an important role in China's national economy. As a crop of industrial material, a cotton variety with good traits requires not only high yield but also excellent fiber quality which could achieve its ultimate commercial value. Therefore, the yield and cotton quality are main object of cotton breeding. Genetic engineering technology provide a new strategy and broad prospects for cotton breeding, but for the improvement of the cotton fiber's quality, it is lack of effective approaches and target genes. Our experiment and follow-up study is to explore the function of fiber-related genes during its development, provide genes for improving the quality of cotton and offer theoretical basis for breeding process on molecular level, eventually achieve our purpose on quality improvement of the cotton fiber.According to its growth characteristics the cotton fibers with different quality from 5~25 days post-anthesis (DPA) of different cotton strains were used as materials, the relative quantitative expression of genes GhExp1, GhExp and XTH related to cotton fiber elongation and GhCAD1, GhCADx, GhCCR1, GhCCR2, GhCCR3 related to secondary wall thickening was analyzed by semi-quantitative RT-PCR respectively, to expore the expression regularity of target genes and investigate the relationships between cotton fiber quality and genes expression at transcriptional level.The experimental results showed that: the expression of GhExp1, GhExp2, XTH, GhCAD1, GhCCR2 and GhCCR3 gene was gradually reduced in the development of cotton fiber, but there was not significant difference in different quality of cotton fiber during developmental stages. The expression of GhCCR1 was relatively stable in 0~25DPA and almost no specificity. The expression of GhCADx is increased in the development of cotton fiber and synchronized with secondary wall development, but an obvious difference existed in cotton fiber with diverse quality: the relative quantitative expression of GhCADx in good quality fiber was significantly lower than the poor quality fiber on 15DPA. This difference had been verified in the 22 different stains of cotton, of which 12 stains were analyzed for two consecutive years, and another 10 stains was analyzed by real-time RT-PCR. GhCADx has higher activity during the fiber development and has an important impact for the formation of cotton fiber quality.The relative quantitative expression of GhCADx gene at different developmental stages of cotton fiber were analyzed by conventional semi-quantitative RT-PCR, QuantumRNA? 18S internal standard relative quantitative RT-PCR and real-time RT-PCR respectively. The stability of internal standard expression was also tested. Results showed that different methods obtained similar results. Though three methods have their advantages and disadvantages, all of them are useful tools for testing of gene relative quantitative expression. Among internal standards, ubiquitin andβ-actin were consistently expressed internal standards during cotton fiber developed.