关键词: 烤烟, 硬度, 淀粉, 总糖, 还原糖, 基因表达

Abstract: 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 NtAGPS, NtGBSS, NtSS, NtSBE and NtISO showed a tendency of decreasing. Among them the expression of tobacco amylopectin synthesis related genes NtSS, NtSBE and NtISO 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, NtSPS, NtSuS and NtVIN 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.

Key words: flue-cured tobacco, hardness, starch, total sugar, reducing sugar, gene expression