Yang Huijuan

Effects of light attenuation on expression of pivotal genes in carbon and nitrogen metabolism in tobacco leaves

Electrical microscope and reverse transcriptional PCR were used to study starch accumulation and genes expression involved in starch, sugar and nitrogen pathway in tobacco leaves. Four light attenuation treatments(100%, 85%, 70% and 55% of natural light intensity respectively) achieved by shading were applied and tobacco leaves were sampled at 78 d, 85 d, 105 d after transplanting and 120 d at harvesting. Results showed that starch reacted the strongest to light intensity. It decreased with the reduction of light intensity before 105 d. Expression of four genes involved in sugar metabolism became lower with the decrease of light intensity and also in line with tobacco maturing process. GBSSI gene expressed at a low level in samples on 78 d during which tobacco leaf was in the progress of expansion, while gene expression increased dramatically on 85 d when leaves had entered maturing stage. The expression of isoenzyme genes of Nirfamily and GS family showed certain complementary effect. The expression level of genes in general decreased with light attenuation, indicating that low light intensity delayed nitrogen metabolism expression.