The Regulation Of Related Enzymes On Carbohydrate Metabolism Of Cucumber Callus In Different Carbon Sources

Cucumber is an important vegetable cultivated world-wide, often encountered starvaton stress due to inadequate supply of assimilates in discomfort environments. the process of vegetative growth and reproductive growth is often for a long time in Cucumber cultivation at the same time, reasonably the source-sink relationship is the key to obtain high yield and good quality during this period. Stachyose is the main form of transport over long distances in cucurbitaceae plants such as cucumber. Compared with sucrose transport type plants, cucumber photosynthate metabolic pathways involved a number of different sugars and enzymes. Sucrose non-fermenting protein kinase1(SnRK1) is an important sugar signaling molecules to regulate plant responsible to sink-source level. At present, There are few studies about related enzymes of sugar metabolism in cucumber source-sink organs to respond to starvation stress and different source-sink levels.1、Cucumber callus grown in Sucrose MS medium as carbon source, cucumber callus mainly contain sucrose, glucose and fructose, the content of raffinose and stachyose is very low. Transferring callus into the sugar-free medium to intimate "hunger" stress, the content of various kinds of soluble sugar reduce gradually. when transfer respectively into four carbon sources include sucrose, stachyose, raffinose and galactose, the content of four kinds of sugar in the callus increased significantly, while the others did not change significantly, showed that callus can absorb the above four kinds of sugar.2、With the loss of the soluble sugar content under starvation stress in Cucumber callus, the expression level and activity of SPS, SS on sucrose metabolism were significantly decreased. The mRNA expression levels of Alkaline α-galactosidaseI were significantly increased, possibly alkaline α-galactosidase I may the key enzyme responsible for the decomposition of polysaccharide for the body to survive. The mRNA expression level of GolS、RS and STS on stachyose synthesis metabolism were significantly reduced, may be due to plant may inhibit anabolic metabolism under the conditions of photosynthate in short supply.3、When transferred cucumber callus into sucrose carbon source, the mRNA expression level and activity of sucrose phosphate synthase (SPS), sucrose synthase (SS) increased. The mRNA expression levels and activities of Galactokinase (GK) and UDP-galactose pyrophosphorylase (UGPase) were reduced, the product sucrose content may be higher and inhibit UGPase the GK expressions and activities. The mRNA expression of acid a-galactosidase III, alkaline a-galactosidase I and a-galactosidase III were also significantly increased, may a-galactosidase associated signaling molecules involved in sucrose regulation network. cucumber callus was transferred into stachyose carbon sources, The mRNA expression and activity of GK was downregulated, The specific regulatory mechanisms for need further study. The mRNA expression of alkaline a-galactosidase I was significantly increased, indicating that the alkaline a-galactosidase I may play the role of decomposition stachyose.When transferred cucumber callus into raffinose carbon source, the mRNA expression levels of alkaline a-galactosidase I and alkaline a-galactosidase II were increased., suggests that these two forms ofa-galactosidase might play key roles in the process of decomposition of raffinose.When transferred cucumber callus into raffinose carbon source, the mRNA expression levels and activity of AGPase was induced, the specific regulatory mechanism remains to be further research, but this research May be useful for galactose and other metabolic pathways.4、Under starvation stress conditions, the mRNA expression SnRK1, may plant metabolic pathways and stachyose transportation type are more complex, it remains to be further research. Transferring cucumber callus into four kinds of carbon sources, the research results show that the SnRK1mRNA expression levels drop, may under the condition of assimilate supply adequate, SnRK1expression level decreased. The mRNA expression of SnRK1showed a trend of rising but still below the level control under starvation stress condition. In Sucrose and stachyose carbon sources, the mRNA expression level of SnRK1was gradually rising; In raffinose carbon source, the mRNA expression level of SnRK1was gradually reduced; In galactose carbon source, the mRNA expression level of SnRK1remains low. The results showed that different carbon sources may have the effect on mRNA expression level of SnRK1.