Genotype Difference Study On Nitrogen Efficiency Of Tea Plants(Camellia Sinensis) And Clonong, Expression Analysis Of Nitrate Reductase

Tea (Camellia sinensis) is one of the most important economic plants in China, the application of chemical fertilizer is the most immediate way to raise the ecomomic yeild of tea plants. At present, more and more chemical fertilizer was using, however, the N application level was decreasing, leading to environmental pollution, aggravation of ecological condition, ect. To settle this problem fundamentally, the nitrogen metabolism regulation network should be studied based on genetics, the aim is to select high N effiency genotype, then select and breed new tea cultivars of low nitrogen tolerance. Finnally, the usage of chemical fertilizer could be decreased and the N utilization efficiency could be improved.The expression of NR, GOGAT and GS in various tea cultivas were studied via using qRT-PCR technology, with first-bud-and-first-leave of 25 cultivas taken in spring. The results revealed abvious differences among different tea cultivars, and there was positive correlation among the three genes. Maybe the nitrogen uptake and utilization efficiency differ among different varieties of of tea plants, and there are some close relationship among the three genes in nitrogen metablism regulation network.On the basis of studies that preceded, the study on Nitrate Reductase (NR) could help to understand nitrogen metablism, nitrate reductase is a key enzyme in the process of nitrogen metabolism. The cDNA of NR gene in Camellia sinensis was amplified via RACE technology by the EST taken from the transcript library of whole organs in tea plants. the cDNA full-length was 2927bp, with 2652bp ORF encordingg 884 amino acid, the molecular weight was 99.6kD, the accession number was JX987133, the sequence was 74% similar to that of tobacco by BlastX. The deduced NR protein is hydrophobic located in the cytoplasm, and transmenbrane domain doesn’t exsit. According to the analysis of relevant software, the presences of several binding sites in the promoter area of NR implicated NR is likely to be regulated by carbon metabolism, and several tissue specific cis-acting elements closely related with growth of plants were detected.Under different N application levels, a pot experiment with three tea cultivars were conducted to study expression levels on different tissues using qRT-PCR technology, meanwhile, content of soluble protein and soluble sugar were measured. The resi indicated that NR gene exhibited tissue-specificity and mainly distributed in roots. Un the nitrogen stress, the expression level of NR in roots increased rapidly to 1.75-15.06 times of control, then the expression level were decreasing all time after 7 days. With the prolongation of nitrogen stress, content of soluble protein showed the trendency of decreasing, while content of soluble sugar first increased, then decreased.