A full-length cDNA that encodes the rice chloroplastic glutamine synthetase 2 gene was isolated from a Minghui 63-normalized cDNA library; and GS2 rice transformants were obtained by an Agrobacterium tumefaciens-media...A full-length cDNA that encodes the rice chloroplastic glutamine synthetase 2 gene was isolated from a Minghui 63-normalized cDNA library; and GS2 rice transformants were obtained by an Agrobacterium tumefaciens-mediated transformation method. Transcripts of the GS2 gene were shown to accumulate at higher levels in the primary transgenic plants in the T0 generation; whereas plants in the T1 generation exhibited a co-suppressed chlorosis phenotype (yellow leaves) accompanied by decreased plant height, few tillers and decreased dry weight. The plants with yellow leaves also displayed a significant decline in GS2 messenger RNA (mRNA) transcriptional level and chlorophyll content; a decrease in total GS activities of ~50% was also found. Although there was no decrease in the concentration of total free amino acids, a change in the concentration of individual amino acids was observed. Our result also indicates a decreased metabolic level (soluble protein content and ammonium concentration) in GS2 co-suppressed plants. A correlation between chlorophyll content and GS2 mRNA expression level was also observed. The GS2 co-suppressed plants showed better performance when complemented with exogenous glutamine, indicating that the lack of an organic nitrogen pool inside the cell is the possible reason for the chlorosis phenotype of the transformants.展开更多
基金supported in part by grants from the National Basic Research Program of China (Grant No. 2005CB120905)the National Special Key Project of China on Functional Genomics of Major Plants and Animalsthe National Natural Science Foundation of China and the Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China (Grant No. 707045)
文摘A full-length cDNA that encodes the rice chloroplastic glutamine synthetase 2 gene was isolated from a Minghui 63-normalized cDNA library; and GS2 rice transformants were obtained by an Agrobacterium tumefaciens-mediated transformation method. Transcripts of the GS2 gene were shown to accumulate at higher levels in the primary transgenic plants in the T0 generation; whereas plants in the T1 generation exhibited a co-suppressed chlorosis phenotype (yellow leaves) accompanied by decreased plant height, few tillers and decreased dry weight. The plants with yellow leaves also displayed a significant decline in GS2 messenger RNA (mRNA) transcriptional level and chlorophyll content; a decrease in total GS activities of ~50% was also found. Although there was no decrease in the concentration of total free amino acids, a change in the concentration of individual amino acids was observed. Our result also indicates a decreased metabolic level (soluble protein content and ammonium concentration) in GS2 co-suppressed plants. A correlation between chlorophyll content and GS2 mRNA expression level was also observed. The GS2 co-suppressed plants showed better performance when complemented with exogenous glutamine, indicating that the lack of an organic nitrogen pool inside the cell is the possible reason for the chlorosis phenotype of the transformants.
