Abstract: 【Objective】 Rice leaf mutant was used to study molecular mechanisms of leaf traits, and to identify the related novel rolling genes in rice.【Method】 The mutant with narrow and rolling leaves was derived from the indica cultivar Zhenong34 induced by ethyl methylsulphonate (EMS), named nrl4. At heading stage, nrl4 and WT Zhenong 34 were randomly selected 10 strains to measure the main agronomic traits and chlorophyll content of nrl4 and WT were tested at the same time. The bulliform cells were observed and counted as well as the number of large and small veins in transverse section of blade under the Zeiss microscope. The leaf phenotype of the F₁ plants and F₂ population which derived from the crossing of nrl4 with Zhenong 34 were investigated and the segregation ratio of normal and rolling leaves were analyzed by chi-square test in the F₂ population. The F₂ population from crossing of nrl4 with Zhenong 104 was used for genetic analysis and gene fine mapping. Five genes in the located region were analyzed by gene quantitative expression. 【Result】 Morphological analysis showed that all leaves of mutant nrl4 were narrow and rolling. In addition, compared with wild type Zhenong 34, plant height, seed setting rate in main panicle and pigment content of mutant nrl4 were increased, as well as grain length of nrl4, but the width of grain was decreased. Leaf angles of functional leaves were all decreased leading to more erecting plant type. Statistical analysis suggested that the rolling leaf phenotype might be caused by the change of number and size of bulliform cells which especially existed at the adaxial side of blade; moreover, in accordance with reduced leaf blade width, leaves of nrl4 contain a decreased number of large veins and small veins. There were 6.0 small veins between two large veins on one side of main vein averagely in mutant nrl4 leaf while there were 4.5 in wild type Zhenong34. Genetic analysis indicated that the mutant trait was controlled by a single recessive gene, the gene nrl4 was located in a confined region of 53 kb flanked by two InDel makers 3M11103 and 3M1115 on the long arm of chromosome 3, where five annotated genes were predicted. Based on the result of sequencing, there was no mutation occurred in the gene sequence and promoter sequence of these predicted genes, but strong changes in gene expression pattern of LOC_Os03g19770 according to the real time quantitative PCR. These results are very valuable for further study on this gene. 【Conclusion】 The narrow leaves are related to reduced number of vasculars, moreover the rolling blade of mutant nrl4 mightresulted fromthe decreased area and number of bulliform cells. The mutant nrl4 is controlled by a single recessive nuclear gene, which is located on chromosome 3, between 3M11103 and 3M1115 with a physical distance of 53 kb. No nucleotide sequence mutation was found to occur in the gene sequence or the 5′UTR of all annotated genes, but the expression of LOC_Os03g19770 is strongly promoted in mutant nrl4, which is 17.5 times of wild type and it may be the candidate gene.

Key words: rice (Oryza sativa L.), narrow and rolling leaf mutant, phenotype analysis, genetic analysis, gene mapping