采后烟叶软化与淀粉、糖代谢及相关基因表达的研究

Study on Softening and Metabolism of Starch and Sugar and Related Gene Expression in Postharvest Tobacco Leaves

为探究采后离体烟叶内淀粉和糖代谢变化规律,及其与采后烟叶软化的关系,以烤烟品种豫烟12号为材料,测定采后烟叶硬度、呼吸强度、总糖、还原糖和淀粉含量变化,并对淀粉和糖代谢相关基因的表达水平进行分析。结果表明:采后烟叶硬度逐渐下降,且与淀粉含量变化呈显著正相关(r=0.827*),与总糖和还原糖含量变化呈极显著负相关(r=-0.964**、-0.958**)。离体烟叶内淀粉合成代谢相关酶基因Nt AGPS、Nt GBSS、Nt SS、Nt SBE和Nt ISO的表达量呈下降趋势,其中烟叶支链淀粉合成酶基因Nt SS、Nt SBE和Nt ISO表达量在烟叶离体18 h内仍维持较高水平,24 h后急速下降;淀粉水解酶基因Ntα-amylase和Ntβ-amylase,以及糖代谢相关酶基因Nt SPS、Nt Su S和Nt VIN表达量呈先上调后下降趋势;即采后烟叶淀粉合成代谢减弱,分解代谢加强,同时糖代谢逐渐旺盛,当糖代谢底物消耗殆尽或叶片衰老至一定程度,糖代谢又减弱。

In order to investigate the changing rule of starch and sugar metabolism in harvested tobacco leaves,and its relationship with tobacco softening,flue-cured tobacco variety Yuyan 12 was taken as sample material to test the changes occurred in hardness,respiratory intensity,contents of total sugar,reducing sugar and starch in harvested tobacco leaves; and to analyze the expression levels of genes related to starch and glucose metabolism. The results indicated that the hardness of harvested tobacco leaves declined gradually,showing positive correlation with the changes in starch content（ r = 0.827＊）,and negative correlation with the contents of total sugar and reducing sugar（ r=-0.964＊＊,-0.958＊＊）. The expression of starch synthesis related genes Nt AGPS,Nt GBSS,Nt SS,Nt SBE and Nt ISO showed a tendency of decreasing. Among them the expression of tobacco amylopectin synthesis related genes Nt SS,Nt SBE and Nt ISO in harvested tobacco leaves within 18 h still could maintain a higher level,but 24 h later decreased rapidly. The expression levels of Ntα-amylase,Ntβ-amylase,Nt SPS,Nt Su S and Nt VIN rose first and then decreased. In the harvested tobacco leaves,starch anabolism was weaken,and starch catabolism was strengthened. At the same time,glucose metabolism was gradually exuberant. When the sugar metabolism substrate was depleted or leaf blade aged to a certain extent,the glucose metabolism was weakened again.