Mechanisms Of Nitric Oxide In The Regulation Of Chilling Stress Tolerance In Cucumber

Chilling stress, one of the abiotic stresses among in the nature, is the mainly limiting factor of temperate crops such as cucumber quality improved and agricultural production. Therefore, understanding that how the cucumber sense and defense the chilling stress plays an important role to improve the level of production and economic benefits and progress the key trait-related breeding process. In this study, Cucumber varieties of different temperature sensitivities were used to explore the effects of exogenous nitric oxide donor sodium nitroprusside (SNP) on chilling tolerance in seedlings.The main results are as follows:1. The chilling damage index and content of relative electrolyte leakage decreased significantly with suitable concentration of NO whichNO treatment could improve chilling tolerance and decrease the chilling damage in cucumber seedlings under the chilling stress.The most effective concentration of NO spraying for chilling enhancing is1.00mmol/L, and the chilling damage index of ZN407and ZN461were declined by42.43%and44.37.37%respectively compared with control.2. Compared with control, Spraying suitable NO can increased the activity of antioxidases superoxide dismutase (SOD)、catalase (CAT) and peroxidase (POD), and the ratio of variable to maximal fluorescence (Fv/Fm) under the chilling stress. Higher activities of antioxidases and Fv/Fm could cause low level relative electrolyte leakage accumulation and photoinhibition in cucumber seedlings.3. NO treatment could reduce the chilling injury by increasing the content of soluble sugar and the content of solube protein, under the chilling stress. However there was no difference in proline content, which indicated that the content of proline was not correlated with the enhancement of chilling tolerance by spraying NO in cucumber seedling under the chilling stress.4. Two in-dependent pathways produced NO were identified from cucumber, one is CuNOA1and the other is Nitrate reductase (NR). Mitochondria localized CuNOAl is induced under chillingstress. Functionally, CuNOAl repaired the noal mutant phenotype in Arabidopsis. Overexpression transgenic lines in Arabidopsis enhance their tolerance to chilling stress, suggesting this gene may involve in anti-cold pathway. RNAi transgenic lines in cucumber shows a weaker tolerance to chilling stress than that of Overexpression transgenic lines in cucumber.6. Expression CuNOAl under chilling stress in OE and Ri transgenic lines affects the content of starch. Starch accumulated owns to SS1and SS3higher expression and SA1low expression.