Gene Mapping Of A Narrow Leaf Mutant(nal9) In Rice

Rice (Oryza sativa L.) is one of the most important crops in the world, and is thegraminaceous represent of the monocotyledonous plants.At present, improving the qualityand yield of rice are still the focus of rice research. And the plant type is one of the mostimportant way of modern high yield breeding. In plant-type research, research of the leaf isone of the key. Researched its growth and genetic control mechanism, is very important forimprovement yield and plant type of the rice.In our study, we obtained a recessive narrow leaf mutant L79, among backcrosses ofGuiChao2generated to a DongXiang wild rice introgression line. The results revealed thatthere was only one recessive nuclear gene locus, involved in the control of the narrow leafphenotype of the mutant. The morphological and physiological characteristics of themutant were investigated. And, the mutant of narrow leaf gene was mapped by usingmolecular markers. Further, we selected target gene and its cloning, sequence analysis andfunction prediction. The main results are summarized as follows:1. Narrow leaf mutant morphological feature analysisThe data from narrow leaf mutant line L79and wild-type GuiChao2phenotype wassurveyed on field. The mutant displayed a significant phenotype of narrow leaf, short andthin stem. Other phenotype was similar to the wild type GuiChao2.2. Genetic analysis and mapping of the NAL9gene using molecular markersThe mutant L79crossed with GuiChao2, all the F1progenies were the normal leaftype, indicated that the narrow leaf mutant was controlled by a recessive gene. The F1plants were self-crossed, the separation ratio of normal leaf progenies to narrow leafprogenies was3:1in F2population. Further it revealed that there was only one recessivenuclear gene, controlling the narrow leaf phenotype of the mutant. According to the resultsof genetic analysis, using SSR and Indel markers linked with the narrow leaf gene, theposition of NAL9was further narrowed down to about500kb in the short arm region ofchromosome3.3. Gene Chips and Real-time PCR expression analysisThe results showed that there was a gene in the target region, and reachedsignificantly differential expression of mutant L79and GuiChao2. According to sequenceanalysis and annotation information, NAL9was identified as target gene, its mutant isnal9(t). The target gene was further validated by using RT-PCR, the results showed therelative expression level of NAL9in wild-type GuiChao2was significantly higher thanthe mutant L79in the leaves, and was up to more than2times.4. Sequence analysis and predicted function of the target geneThe NAL9gene was located at20589-145290of the BAC clone, containing1646nucleotides, and the length of cDNA was1584bp, encoding a527amino acid protein. Theresults of sequence analysis showed that the mutant nal9carried a single base substitution in the exon (Ato G), and the corresponding amino acid from valine to alanine, however thestructure of translated protein did not change significantly.