Development Of High-yield Line By Over-expressing TAL Gene In Rice

Rice is one of the most important crops and plays a decisive role in food safety in China.Rice grain yield are determined by panicle number per plant,grain number per panicle and grain weight,which are controlled by multiple genes.Now,a more effective strategy is needed for further improvement of rice yield potential.Molecular breeding,based on yield-related genes and their interaction,is considered as the effective strategy to break the yield ceiling.Cloning and functional characterization of the genes regulating rice important agricultural traits is the fundament for high-yield molecular breeding.In this study,we characterized a TAL gene which encodes transaldolase in rice.Several homozygous and stable RNAi and over-expression transgenic lines under Wuyunjing 7 background were generated and used for histomorphological and physiological analysis.The primary genetic and physiological mechanism of TAL for rice grain yield regulation was revealed and the main results are as follows:1.Subcellular localization indicated that the TAL protein is localized at nucleus,cytoplasm,and plasma membrane.2.The TAL gene has pleiotropic effects on multiple aspects in plant growth and development.From seedling stage to mature stage,the TAL over-expression lines showed stronger growth potential when compared with wild-type Wuyunjing 7.While down-regulation of TAL gene led to short and weak plants.3.The TAL gene also plays key roles in the vascular development of flag leaves and stems.Overexpression of TAL increased the number of small vascular bundles,but had no effect on the number of large vascular bundles in flag leaves.However,the number of both large and small vascular bundles in stems were significantly increased in the over-expression lines.As expected,the number of vascular bundles were decreased in the RNAi lines.4.The transpiration rate,net photosynthetic rate,stomatal conductance of flag.leaves in TAL over-expression lines were much higher than those in wild-type.However,the interc ellular CO2 concentration was significantly lower.And an opposed phenotype was detecte d in the RNAi lines.These data suggested that TAL gene positively regulation rice photo synthesis.5.Several yield components were affected in the transgenic lines.1000-grain weight and grain number per panicle increased by 7.1?7.9%and 13.2?15.3%,respectively,in the over_expression lines.Finally,the grain yield per plant was improved by 18.5?20.7%and the population yield was increased by 10.6?12.4%.In contrast,1000-grain weight,grain number per panicle and yield were sharply decreased in the RNAi lines.Taken together,TAL gene has potential value,in rice breeding,and maybe an important target site in yield enhancement though genetic engineering strategy.