| Nitrogen is the essential macronutrients for rice growth and development,and the blind pursuit of high yield of rice,the amount of nitrogen fertilizer is also increasing,which leads to the pollution of the environment,therefore,the exploring of rice nitrogen tolerant gene,breeding rice varieties with high nitrogen efficiency has important significance to the sustainable development of agriculture.In this study,a total of 67 substitution lines were constructed by using japonica rice variety Asominori as receptor and indica rice variety IR24 as inserted fragments.Based on the identification of low nitrogen stress in the field,four low nitrogen insensitive families(Y1997,Y1998,Y1999,Y2000)were selected.In the laboratory,the phenotype of hydroponic culture also showed low nitrogen insensitivity.Through the gene analysis of low nitrogen QTL in the field,and combining with the displacement map,the RNA-seq data and the quantitative results,the AS gene of low nitrogen tolerance in rice was located,and its possible function was analyzed.The main results are as follows:1.QTL mapping of traits related to low nitrogen stress.Using QTL Ici Mapping software to calculate QTL.The composite interval(CIM)plot method was used to detect the correlation between the QTL and the additive effect value and the total variation of the corresponding traits by the available genetic map of rice.By using the available genetic map of rice,the LOD value is equal to 2.5.A total of 8 loci related to relative plant height and tiller and relative tiller were detected,which were distributed on 6 chromosomes.A total of 10 QTL related to plant height were detected,and the LOD values ranged from 2.56 to 7.45,were located in chromosomes of 2,3,4,7 and 12,respectively.The range of phenotypic variation explained was 1.32%-6.74%.On the relative plant height index,the LOD value of QTL in the vicinity of third(RM7)chromosome was 7.45,the contribution rate was 6.74%,which was the highest contribution rate of QTL in the 6 relative strains.A total of 3 QTL related to tiller were detected,and the LOD value ranged from 2.53 to 2.76,and there were about 3 QTL related to tiller,which were located on chromosome first and chromosome 2,the range of phenotypic variation explained was 17.08%-19.34%.2.Because of insert the RM7 IR24 fragment of AS gene,the amino acid sequence changed,Y1997,Y1998,Y1999,Y2000 of four families in the field of tolerance to low nitrogen stress on plant height and tiller ratio was higher than the parent ASO and IR24 frequency in the field.Under the condition of low nitrogen stress,the relative dry weight ratio and relative dry weight ratio were higher than that of ASO and IR24 in lab,and the frequency distribution maps were similar to normal distribution,and the relative expression of target gene was significantly diverse under different nitrogen concentrations.Genetic analysis show that the IR24 gene of the six exons of the AS gene was deleted in the thirteenth exons,resulting in the deletion of amino acid sequence.The target gene is a member of the aminotransferase family.The amino acid sequence of AS-B in different plants is very high and the similarity is 70%-80%.It is a kind of very conserved protein.The chloroplasts composed of chlorophyll in Rice leaf,they are main organ for photosynthesis of plants and is the foundation of rice yield.Further study of chloroplast development regulation mechanism will provide enlightenment for us,so that we can cultivate high-yielding crop varieties.Using EMS mutagenesis acquire a mutant NJ4 and Seedling mutant white stripe btw,we cloned a new rice leaf color gene btw by map-based cloning.1.Compared with wild type plants,btw mutants appear white stripes traits,chlorophyll a content decreased by 55.3%,chlorophyll b fell by 57.1%and Carotenoid declined 37.4%.Transmission electron microscopy(sem)observed that the numbers of thylakoid reduced and lamella structure is arranged loosely in the chloroplast of mutant,in addition,agronomic traits survey also show that btw mutant have lower plant height,leaf length,sword leaf width,ear length and effective tillering,thousand grain quality,than wild type.2.Utilizing white stripes mutant btw and japonica rice varieties NanJing 11 to hybrid F2 group for gene location,preliminary location on chromosome 3 long arm,further development of molecular markers to shorten the positioning range in the 140 KB area,the area contains 13 candidate genes.By sequencing comparative analysis found that mutations occur on LOC_Os03g11110 gene,its 856th base occur single-base substitution in coding region and replaced by the 'C' with 'T',and lead to amino acid leucine into phenylalanine,the gene function remains to be studied. |
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