Effect Of Shading And Salt Stress On RFOs Synthesis And SnRK1 Expression In Cucumber Seedings

Cucumber is one of the most important global cultivated vegetables, while it often subjected to a variety of abiotic stress during the cultivation process. Raffinose family oligosaccharides (RFOs) are the major transport forms of photosynthetic carbon assimilates in cucumber. Minewhile, RFOs accumulate in cells and could play the role in protection when the cucumber subjected to the adversity stress, while the regulation mechanism is unclear. The effect of SnRKl on the central adjustment of the sucrose transportation plant under stress has been studied, while the regulation function of SnRK1 in RFOs-transporting plant under abiotic stress is limited. In this study, to figure out the effect of stress, such as light stress, salt stress and hormone on physiological indexes in cucumber, and in order to provide preliminary data for responsion mechanism in plant under abiotic stress, improving the basis technology of cucumber cultivation under the adversity, we investigated the soluble sugar content, mRNA expression levels and actives of some key enzymes related to sugar metabolism in cucumber seedlings with for leaves under shading, NaCl stress and ABA treatment, The results are as follows:1 Shading treatment can increase the sucrose content in cucumber leaves, but it reduced the galactinol, raffinose and stachyose contents,the transcription of galactinol synthase (GolS) gene (GolS1, GolS2, GolS3, GolS4), raffinose synthase (RS) gene and stachyose synthase (STS) (STS1 STS2,STS3) decreased, and the activity of GolS and STS decreased, but the effect on the activity of RS is not significant. The expression of SnRK1 increased significantly under the shading condition. The decrease amplitude of GolS in GolS4 gene was the biggest after shading treatment, and may play an important role in the regulation of the process of the assimilation of synthesis after shading stress.2 NaCl stress induced upregulation on the accumulation of the content sucrose, raffinose, galactinol and stachyose. The expression level of GolS7,3 in cucumber leaves was lower, while Gols2 was significantly higher than those of control. And the expression level and activity of Gols2 were consistent with the accumulation of galactinol. The expression level and activity of RS and STS increased under NaCl stress, compared to the control.The SnRKl mRNA levels was significantly higher than that of control in cucumber under NaC1 stress. These results indicated that GolS2, STS, RS and SnRKl play an important role in the metabolism of cucumber seedlings under salt stress.3 When cucumber seedlings leaves spraying with 0.2mmol/L ABA, the expression levels and activity of GolS, RS and STS, and RFOs concentration were increased quickly. We have also found that the expression of SnRKl was significantly increased in cucumber seedlings under ABA treatment.These results suggest that shading treatment reduced the assimilative capacity of cucumber, cucumber leaves under shading conditions could not ease the stress damage by accumulation RFOs, but the accumulation of RFOs under salt stress may play a protective role like sucrose transporting plants. ABA can induce the synthesis of RFOs and SnRKl expression in cucumber, the expression of SnRKl in leaves of cucumber seedlings under shading and salt stress increased show that it may play a same role like in sucrose transporting plants in adversity.