Study On Respiration Of Tobacco Leaves And Gene Expression Related To Carbon Metabolism In Postharvest Tobacco

Respiratory metabolism and carbon metabolism are the most basic metabolic activities during growth and development.They play an important role in determining tobacco baking characteristics and rationally adjusting baking process.In order to investigate the change rule of respiration intensity and carbon metabolism in Postharvest tobacco leaves,the respiratory intensity of tobacco leaves at different temperatures and different degrees of water loss in the process of dark box was determined;the flue-cured tobacco varieties “Yuyan 12” and “Qinyan 96” were taken as the sample materials to determine the changes of starch,total sugar,and reducing sugar contents,and the expression levels of starch and sucrose metabolism related genes in tobacco leaves after harvest were analyzed by real-time fluorescence quantitative PCR.The main results are as follows:1.The respiratory intensity of postharvest tobacco leaves is a double-peak curve,the increase of respiratory intensity may be related to mildew of tobacco leaves at the end of experiment.The respiration intensity of fresh tobacco leaves is the upper leaves> the middle leaves > the lower leaves,the two peaks of respiration intensity of the lower leaves are close to each other,and the variation range is not obvious.The temperature sensitivity of different parts of tobacco leaves is different.The respiration intensity of the lower tobacco leaves gradually decreases with the rise of temperature.The respiration metabolism of the middle tobacco leaves is the most stable,while the upper tobacco leaves with the temperature increase gradually upward trend.At different parts of the tobacco leaves at different temperatures,the peak of tobacco respiration intensity changes and the duration is different.The lower tobacco leaves were the highest at 38 degrees centigrade,and the respiratory intensity of the middle tobacco leaves were higher at 40 degrees Celsius,while the upper leaves were the highest at 42 degrees centigrade.The respiration intensity of fresh tobacco was improved after water loss treatment,but the respiration intensity of tobacco leaves in different parts was different from that of the degree of water loss.The peak of 10% respiration intensity in the lower leaves of the lower part of the dark box was higher than that of CK.The first and second respiration peak times of the 20% tobacco leaves were earlier and delayed,respectively.The respiration intensity of 30% tobacco leaves was lower than that of CK,but the water loss of the middle and upper leaves decreased by 20% and 10% respectively.In the middle leaves,the water loss was 20%,and the respiration intensity was obviously improved.The water loss of upper tobacco was 10% and the respiration intensity was obviously improved.2.The results indicated that the starch content of “Qin 96” was significantly higher than that of “Yu 12”.Starch content decreased gradually after harvested for 0-30 h,while total sugar and reducing sugar gradually increased,and sugar content increased rapidly after 12 h.The expression of Nt AGPS3,Nt GBSS1,Nt SS1,Nt SS2,Nt SBE1,Nt SBE2,Nt ISO2,Nt ISO3,Nt SP,Nt SPSA,Nt SPSB,Nt SPSC,Nt SPP1,Nt SPP2,Nt Su S and Nt VIN1 in fresh tobacco leaves of “Qin 96” was significantly higher than that of “Yu 12”,while the expression of Nt?-amylase and Nt?-amylase was significantly lower than that of “Yu 12”.The expression levels of Nt AGPS1,Nt AGPS3 and Nt GBSS1 decreased rapidly after harvested for 0-30 h;the expression levels of amylopectin synthesis related genes showed disordered increasing and decreasing;the expression of Nt SR1,Nt?-amylase,Nt?-amylase,Nt SP,Nt SPSA,Nt SPSB,Nt SPSC,Nt SPP1,Nt SPP2,Nt Su S and Nt VIN1 showed the trend of ascending first then descending,or increasing gradually.The expression levels of Nt AGPS1 and Nt GBSS1 were significantly correlated to the changes of starch and sugar contents.These results suggested that there are some differences in starch and sugar metabolism between “Yu 12” and “Qin 96”,and Nt AGPS1 and Nt GBSS1 might be the key genes regulating the carbon metabolism in tobacco leaves after harvest.Starch degradation plays an important role in the softening of leaves of post harvest tobacco.There was a significant correlation between respiratory intensity and starch,total sugar and reducing sugar content.The expression of the gene Nt AGPS1 of the key enzyme of starch metabolism has a direct effect on the tobacco leaf respiratory intensity.