Map-based Cloning And Molecular Regulation Mechansim Of Leaf Width Gene QFLW7 And OsNAAL1 In Rice (Oryza Sativa L.)

Identifying genes that are beneficial to yield and exploring yield potential are important goals in the breeding of super-rice(Oryza sativa L.).Controlling leaf shape at the molecular level,modulating the "source-flux-sink" relationship,and increasing photosynthesis efficiency can lead to the production of high-yield rice.In the present study,we used the high-yielding Indica rice cultivar YangDao6(93-11)and the high-quality Japonica rice cultivar Nipponbare(NPB)as parental strains,since both of these have well-characterized genetic backgrounds and completely sequenced genomes.In a previous study,recombinant inbred lines(RILs)were generated using these parental cultivars,and mapping of the leaf width QTL qFLW7 for regulating leaf width at the heading stage was also carried out.Based on the information thus obtained,93-11 and NPB were usedas mutual donors for QTL qFLW7 fragments.The corresponding recipient parents were used as the recurrent parents to generate two near-isogenic lines(NILs),NIL-FLW79311 and NIL-FLW7NPB,in order to clone the FLW7 gene related to leaf width regulation,which was then functionally analyzed and examined for its utility in breeding for higher yield.The main results are as follow:1.The leaf width quantitative trait locus qFLW7 was detected in recombinant inbred lines derived from a cross between the 93-11 and Nipponbare(NPB)rice varieties.Map-based cloning showed that leaf width qFLW7 was allelic to the GRAIN LENGTH 7/GRAIN WIDTH 7 gene associated with grain size,which the additive effect allele was from 93-11.2.Compared with the recurrent parent NPB,the number of small vascular bundles,flag leaf width and area were increased in NIL-FLW793-11.In contrast,compared with the recurrent parent 93-11,those traits were decreased in NIL-FLW7NPB.3.qRT-PCR analysis of the two candidate genes at the heading stage showed no significant difference in LOC_Os07g41190 expression between NIL-FLW7NPB and the recurrent parent 93-11,whereas the expression level of NIL-FLW7NPB LOC_Os07g41200 was 4.51 times higher than that of 93-11.4.Overexpression line of OsFLW7 decreased leaf width and area,whereas inhibiting OsFLW7 had the opposite effect,suggesting that a combination of OsFLW7 upregulation and reduced gene function leads to an increase in grain length.5.In addition to regulating leaf morphology,OsFLW7 also modulates leaf tissue structure,which in turn affects leaf photosynthesis rate.A decrease in OsFLW7 function could increase the light-receiving area of rice leaves and thereby enhance photosynthesis efficiency.6.Measurement of plot actual yield confirmed that the grain length and 1000-grain weight were all higher than that of NPB,and the field actual rice yield per hectare of NIL-FLW793-11 was thus 10.05%higher than that of NPB.In the present study,another study material narrow albino leaf 1(naal1),was obtained from a rice mutant population generated from an EMS-induced indica variety Shuhui527(SH527).Map-based cloning results of the mutant identified the regulatory gene named NARROW ALBINO LEAF 1(NAAL1).In this study,the function of NAAL1 was studied and the roles of NAAL1 in rice leaf morphogenesis,metabolic auxin regulation,and the rice yield formation were examined.The main results are as follow:1.The mutant was characterized as a dwarfed plant with upper-surface(adaxial)albino leaves and normal lower-surface color.2.The number of large and small trichomes of the adaxial and abaxial surfaces of naal1 leaves increased relative to wild type.The chloroplast structure in naal1 and SH527 was observed by TEM showed fewer chloroplast membranes on the naall adaxial surface as compared to SH527.The number of the main and secondary veins in naal1 was also reduced compared to SH527.3.Map-based cloning showed that OsNAAL1 was located on the chromosome 7,and encodes the CHR4/MI-2-like protein.This complementation test showed that LOC_Os07g31450 is the target gene OsNAAL1.4.OsNAAL1 was constitutively expressed in the rice root,stem,leaf sheath,and panicle,and OsNAAL1 was indicative of a nucleoprotein.5.The narrow-leaf phenotype of naall may be related to the altered transcriptional activity of leaf development-related and auxin-related genes.6.There are responses to different exogenous NAA concentrations on naall.We thought that the OsNAAL1 gene is involved in the tryptophan biosynthesis pathway of auxin production,thereby affecting root development and leaf morphogenesis.