Genetic Identification Of Semi-dwarf Mutant Sd87 And Functional Analysis Of A Low-tillering Mutant Lt8601 In Rice

1.Genetic analysis and gene mapping of a semi-dwarf mutant sd87 in rice.The dwarf gene reduces the height of rice,which could effectively prevent the lodging of rice and optimizes the rice plant type to boost yield.sd87,a Semi-dwarf mutant in the present study,is semi-dwarf throughout the growth period,with reduced leaf length and increased leaf width.Plant height,number of productive panicles per plant,panicle length of primary branch,number of secondary branch of per panicle and seed setting rate of sd87were significantly decreased.However,the number of primary branch of per panicle,1000-grain weight and grain width in sd87 were increased obviously.The internodes of sd87 mutant were shortened,among which the first internode showed a distorted shape and the most obvious length reduction.sd87 mutant seedlings were less sensitive to exogenous brassinosterol（BL）,and sd87 might be a brassinosterol（BR）insensitive mutant.The chlorophyll content and photosynthetic rate increased in sd87 at the heading stage.Statistical analysis of separation ratio proved that the mutant sd87 was controlled by a single recessive nuclear gene.Mutmap analysis suggested that mutant sd87 was interlocked in the middle of chromosome 5.In the interlocked region,base mutations at one,and only one site caused changes in the amino acids encoded by its genes.The localization results of molecular markers were consistent with Mutmap analysis.DNA and c DNA sequencings were performed to verify the candidate genes,and the DNA of sd87gene of the mutant underwent a single base mutation,which resulted in the insertion of76bp base sequence into its c DNA,caused shift of amino acid coding reading frame and the termination of coding ahead of schedule.The candidate gene is an allele of SMOS1/RLA1.Compared with 676R,the expression levels of Dwarf4,D11 and D2,the BR synthesis genes,were higher in sd87.2.Functional analysis of low-tillering mutant lt8601 in rice.The rice panicles,determined by tiller,directly affect the yield level per unit area.In the seedling stage,there was no significant difference between the low-tillering mutant lt8601 and the wild type.The tiller buds of lt8601 at the tillering stage could not grow normally and the tiller number decreased significantly.Compared with 676R,the main agronomic traits of lt8601,especially the number of productive panicles per plant,number of secondary branch of per panicle and the number of primary panicles per panicle,were dramatically reduced.Electrophoretic detection and field phenotype preliminarily showed that the mutant lt8601 was caused by the mutation of lt8601 gene.Through agrobacterium-mediated method,the p C1391Z-LT8601promoter-GUS expression vector was transferred into Japonica rice ZH11,and electrophoresis results showed that T₀generation transgenic plants were positive.The c DNA fragment of LT8601 gene was amplified,and the recombinant co-expression vector of p CAMBIA2300-35S-LT8601-e GFP was obtained through connection,conversion and sequencing.LT8601 gene was expressed in various parts of seedling stage,tillering stage and booting stage,among which the expression of leaves was the highestattillering stage.q RT-PCR showed that the expression levels of MOC1 and MOC2 were higher in lt8601 mutant,while the transcripts of D3,D14and SD87 gene expression level were decreased.