Abstract:

Teanitrite reductase（CsNiR）was cloned by RT-PCR from cDNA isolated from leaves of cultivar‘Longjing 43’. The complete ORF of the CsNiR was 1 764 bpencoding 587 amino acids. Alignment of amino acid sequences showed that CsNiR sharing more than 76% similarities to NiR in Betula pendula，Arabidopsis thaliana，Spinacia oleracea and Oryza sativa. Bioinformatics analysis indicated that the CsNiR was a hydrophilic non-secretory protein with molecular weight 68.648 kD and theoretical pI 6.12. Prediction results by InterProScan showed the secondary structure of CsNiR protein comprised of a hemoprotein beta component and a 4Fe-4S region，and its 3D structure was also predicted  by Swiss Model. qRT-PCR analysis revealed that the expression abundance of CsNiR in mature leaves was the highest among the three tested tissues（two leaves and a bud，mature leaves and roots）. Meanwhile，the transcript changes of CsNiR responding to different nitrogen（N）levels were studied by qRT-PCR after resupplying normal N（1 mmol · L^-1 NH₄NO₃）and low N（0.1 mmol · L^-1 NH₄NO₃）on hydroponic seedlings of three tea varieties with treatment of two week N starvation. The CsNiR expression levels were increased significantly in roots at 2 h and 6 h under normal N treatment，but they were changed since 24 h after N supplied in leaves. Furthermore，the transcription of CsNiR was also different among varieties. The transcript abundance of CsNiR increased more greatly under the normal N condition compared to those under low N treatment. Thus，factors like genotypes，tissues，nitrogen levels should be taken into consideration for the role of CsNiR in nitrogen utilization in tea plants.

Key words: Camellia sinensis, nitrite reductase, cloning, gene expression, nitrogen