Studies On Carbohydrate Metabolism And Related Gene Expression In Floral Buds Of Sand Pears During Dormancy

Dormancy in temperate-zone deciduous fruit trees is the life process that allows trees to survive under unfavourable conditions during the winter. Until now, the mechanism of dormancy regulation has not been clear. Many researches have shown that carbohydrate metabolism that is a basic metabolic pathway of plants plays an important role in dormancy of deciduous fruit trees. The researches on carbohydrate metabolism in pears during dormancy have focused on the relationship between changes of carbohydrate contents and dormancy release. However, few studies have been carried out on the molecular mechanism of carbohydrate metabolism in pears during dormancy. Therefore, changes in carbohydrate contents and expression patterns of genes related to carbohydrate metabolism in pears were studied during dormancy period for two successive years. The main results were as follows:The content of soluble sugars in floral buds of’Cuiguan’pear decreased gradually with increased depth of dormancy, and reached the lowest value on November15. Then the content of soluble sugars increased during endo-dormancy and dormancy release. The starch content in floral buds decreased with increased depth of dormancy. But there was a difference in the occurring date of the lowest content of starch between two years. The starch content increased gradually with the start of dormancy release, and reached maximum value just before the total release of dormancy and then decreased gradually. PpAMY, PpBAM1, PpBAM2and PpPHS in ’Cuiguan’pear showed an expression peak at the final stage of endo-dormancy and then dropped gradually until the total release of dormancy. Thereafter, except for PpBAM2, other three genes up-expressed again. The change in the starch content was closed related with the expression levels of PpAMY, PpBAM1, PpBAM2and PpPHS during the floral buds dormancy of’Cuiguan’pear, which implied that these genes co-regulated starch metabolism in floral buds of’Cuiguan’pear. SuSy, SPS, AGPase and UGPase showed an expression peak before the total release of dormancy in ’Cuiguan’and’Wonhwang’pears. The expressions of all these genes mentioned above would supply material and energy for the release of dormancy. The expression patterns of HK and HisH3varied with cultivars. In conclusion, all these genes expressed coordinatively and regulated carbohydrate metabolism in pears during dormancy.The expression of genes coding starch degradation during dormancy showed different patterns, which was affected by environment. The mainly functional genes for starch degradation differed with cultivars.Dormancy-breaking chemicals are usually used to compensate the lack of natural chilling requirement and stimulate budbreak of deciduous fruit trees. Our results indicated that hydrogen cyanamide (HC) could improve the budbreak of ’Cuiguan’ pear both in the open field and under conditons of plastic tunnel. But Yalin and CaCN2had no effects on’Cuiguan’pear under conditons of plastic tunnel. Hydrogen cyanamide (HC) improved the soluble sugar and starch contents of’Cuiguan’pear in the open filed, but didn’t work on’Cuiguan’pear under conditons of plastic tunnel.