Screening And Identification Of Line With Starch Accumulating In Vascular Bundle Sheath From Rice Genetically Modified With Genes Of Aux/IAA Family

Rice,as a typical C₃ crops,has lower photosynthetic efficiency and yield than that of C₄,such as corn.Using genetic engineering technology to introduce C₄ photosynthesis into rice will provide the possibility for improving the actual yield and productive potential of rice.Transcription factor（TFs）,as a key regulator of gene expression,is essential for regulating downstream gene expression.In this study,by agrobacterium infection,we have transferred 26 genes of Aux/IAA transcription factor family derived from corn into Nipponbare.Transgenic plants with starch accumulating in vascular bundle sheath cells are screened and identified,and that provided material and technique for the study of photosynthesis and product transport mechanism in rice.The results are as follows:1.Overexpression vectors of 26 genes of Aux/IAA family are successfully constructed using recombinant cloning technology.2.Through agrobacterium-mediated approach,the target genes are transferred into‘Nipponbare’rice.The induction rate is 94.66%for the callus.the differentiation rate is84.56%.And the transgenic rate is 100%.3.At the tillering stage,leaves of transgenic plants are made into thin slices and stained with iodine-potassium iodide（I₂-KI）.Vascular bundle sheath cells are stained brown for a total of 2 lines,aux3 and aux8.4.Investigation of agronomic traits show that plant height,1000-grain weight and seed setting rate of aux3 are significantly lower than that of wild type,and there is no significant difference between aux8 and wild type.5.The results of photosynthetic measurement show that the net photosynthetic efficiecy of aux3 decreases,and transpiration rate and stomatal conductance of aux8increase significantly compared with the wild type.6.Starch content of leaf at tillering stage,is significantly higher in transgenic plant than that of wild type.7.Starch-metabolizing genes of transgenic plant show differential expression compared with that of wild type.AGPL1,a key gene of rate-limiting enzyme for starch biosynthesis in transgenic plants,is highly expressed,which is conducive to the synthesis of ADP-glucose in the leaf.In the plant of aux3,the expression of the key gene SUT4,encoding a sucrose transporter（SUTs）,is significantly reduced.It is speculated that sucrose transport may be blocked.In the plant of aux8,the expression level of the key gene GBSSⅡ,encoding starch synthetase（SS）,increases.It is speculated that the starch synthesis may increase,and the decomposition and transportation of starch may not be on time,resulting in excessive starch accumulation.