Effects of exogenous nitric oxide on SBPase gene expression characteristics and photosynthetic rate of Brassica chinensis L. under copper stress

【Objectives】 In order to provide a theoretical basis for comprehensive understanding mechanism of adding exogenous nitric oxide(NO) to alleviate the decline of net photosynthetic rate(Pn), the gene of sedoheptulose-1, 7-bisphosphatase (SBPase) which is one of the key enzymes to restrict RuBP regeneration in calvin cycle was cloned, and the different expression of the SBPase gene in Brassica chinensis L. leavesunder copper stress and adding the SNP was analyzed combined with the net photosynthetic rate changes. 【Methods】 The SBPase gene of Brassica chinensis L. was cloned by RT-PCR, and seedlings of Brassica chinensis L. (named Shanghai green) with three to four real leaves were used as materials. Copper concentration was 200 μmol/L, and the SNP concentration was 300 μmol/L. At the same time, four related groups were set to exclude the disruptive factors. The Pn and the expression of SBPase gene of Brassica chinensis L. leaves at the same position and moment after the treatment of 0, 4, 8 and 12 days were determined. The environmental conditions of the experiment were light intensity, 200 μmol/(m2·s); photoperiod, 12 h; and temperature, 25℃/18℃.【Results】1) The sequence of the open reading frame of SBPase gene is 1182bp, encoding 393 amino acids. The molecular weight of the predicted protein is 42.34kD and the theoretical isoelectric point is 5.85. 2) The sequence analysis show that it contains a redox active site and a 59-amino acid chloroplast transfer peptide. The amino acid sequence has high homology with other SBPase separated from other species. 3) The qRT-PCR analysis show that the SBPase gene expression in Brassica chinensis L.leaves is declined under copper stress, and with time extending the degree of decline is aggravated. Besides, the expression of SBPase gene is increased after the addition of NO. 4) The application of exogenous NO increases the Pn of Brassica chinensis L. leaves under the copper stress, and the variation tendency of Pn and the expression of SBPase gene are in a good agreement. 【Conclusions】The expression of SBPase gene in Brassica chinensis L. leaves is changed under the copper stress and the addition of NO, which may be one of the causes of the change of Pn in Brassica chinensis L. under the copper stress and the addition of NO.