Genetic Analysis And Mapping Of A Narrow Leaf Mutant Nal7-2(t) In Rice

Rice is one of the most important food crops which provides the food for more than 50%of the global population.It is crucial to ensuring food security by increasing rice production.Ideal plant type in which narrow leaf character is an important index was used to improve yield in the breeding.Therefore,it is of great theoretical significance to explore new genes and genetic mechanism of narrow leaf characters for breeding new varieties with ideal plantA mutant named nal7-2(t)was found in the 9311 mutant library.Systematic analysis of agronomic characters of nal7-2(t)was carried out,and a reciprocal cross population was constructed by crossing with 9311 for genetic analysis.Meanwhile,F2 populations generated by crossing with 9516,guichao2hao and 02428 as male parent respectively were used for fine mapping.The candidate genes covering the mapping interval were analyzed.The main results are as follows:1.There was no significant difference between the leaf width of nal7-2(t)and 9311 at seedling stage.The leaf width of nal7-2(t)gradually narrowed from the tillering stage until maturity stage compared with 9311.Agronomic traits analysis showed no significant difference in leaf length,while plant height,1000 grain weight,seed setting rate,grain length,grain width and panicle length were significantly reduced whereas effective tillers significantly increased.The analysis of internode configuration of 9311 and nal7-2(t)showed that the significant reduction of the internode length of nal7-2(t)resulted in the dwarf phenotype2.The decrease of the number of large veins and small veins which account for 70.0%and 48.0%of 9311 respecti’vely caused the narrow leaf phenotype of na17-2(t).3.Genetic analysis showed that the narrow leaf phenotype of nal7-2(t)was controlled by a recessive nuclear genes.4.Using the F2 poputions obtained by crossing with 9516,guichao2hao and 02428 respectively,NAL7-2(t)was narrowed to the 116kb region on the long arm of chromosome 7.Compartive Sequence of candidate genes in the internal revealed a A to C mutantion on exon 2 of LOC_Os07g4029,and the amino acid was changed from aspartic acid to alanine in the encoded protein.Therefore,LOC_Os07g40290 was initially identified as the candidate gene5.Expression analysis showed that LOC_Os07g40290 expressed in roots,stems,leaves and young panicles,with the the highest expression level in young panicles and the lowest expression level in leaf sheath.Further more,in nal7-2(t),the expression level of LOC_Os07g40290 in leaves decreased significantly.6.The expression of NAL7-2(t)was affected by exogenous NAA.The narrow leaf phenotype of nal7-2(t)is not only related to multiple leaf morphological development regulatory genes,but also related to anxin synthesis,transport and signal transduction genes.