Discovery And Functional Analysis Of OsTB1 Alleles For Controlling Rice Culm Thickness

Rice is one of the most important food crops in China,the problem of rice lodging has always been a limiting factor in its high yield.How to solve the problem of rice lodging has become the key to improve the yield of rice.Rice culm is the support of the weight of the whole plant,and its morphology and intensity determine the lodging resistance of the plant.Rice culm thickness is an important factor affecting its strength and lodging resistance.In this study,F2 segregation population was constructed by using indicia rice cultivar 9311 and japonica rice cultivar Nipponbare,the culm diameter was used as the index to analyze the relative characters of culm thickness,F2 population was used to gene linkage analysis and gene mapping.Finally,the thick culm gene TCI from 9311 was mapped to the range of 585 kb between the two markers RM168 and RM1350 on the long arm of Chr.3.OsTB1(TEOSINTE BRANCHED1)is a reported gene that related to rice stem development in the range,the expression level of this gene is positively correlated with the culm diameter,and its allele SCM3(STRONG CULM3)is a major QTL gene controlling the degree of culm strength,so thick culm gene TCI may be one of its alleles.Based on the analysis of the expression level of the gene in several research materials,we found that expression level of the gene in thick culm variety 9311 and its filial generation F1 with slender culm variety Nipponbare has significantly improved compared to Nipponbare.We tested and analyzed an important locus of that gene in many varieties as well,and found that the thick culm varieties in the tested materials were consistent with that of 9311,while the slender culm varieties were consistent with that of Nipponbare,these results indicated that the thick culm gene TCI is probably to be one of OsTBl alleles.Finally,we confirmed that the thick culm gene TC1 from 9311 was one of the alleles of OsTB1 through the functional complementation by genetic transformation.OsTB1 alleles of 9311,Nipponbare,Kasalath and 1060 were cloned and transformed into the gene function loss mutant fc1,which will help to compare the effect of different allele types on culm diameter in the same background;four vectors of gene promoter in different materials for promoter activity analysis were constructed,the expression of GUS was detected to analysis the tissue expression by GUS fusion,which made a good preparation for comparison of the strength of these promoters by quantitatively detecting the expression level of reporter gene GUS in transgenic plants.Last but not least,subcellular localization analysis by rice protoplast transformation experiment determine that the gene expresses in throughout the nucleus and cell membrane.In addition,we found that the expression of OsTBl in thick culm variety Kasalath was abnormal,and discussed the causes of that gene down-regulation expression.We designed related experiment to verify the speculation that we putted forward.