Effects Of Low Temperature Stress On Root Differential Gene Expression And Mitochondrial Physiology And Biochemistry In Sugarcane Seedlings

Sugarcane(Saccharum officinarum L.) belongs to the genus Gramineae, is native to and widely cultivated in tropical and subtropical regions for sugar production. Guangxi is the largest producer of sugarcane and sugar in China. In the present experiment, seedlings of two sugarcane varieties ROC22(cold sensitive) and GT28(cold resistant) were grown in a water planting system, and treated with low temperature in an artificial climate chamber. Samples were taken to study the effects of low temperature on the plant growth, physiological and biochemical characteristics, and differential gene expressions in roots and root mitochondria of sugarcane. The results were as follows.1. The sugarcne water planting system was further improved. It was found that4days of plant growth had little effect on the nutrient solution for culture, and it should be the best to replace the nutrient solution every three days.2. Under low temperature treatment, the plant roots grew slowly or stopped, and the apical was getting rot. The root activity was positively related to the cold resistance of different sugarcane varieties. The root relative conductivity increased significantly under low temperature treatment, but no significant difference was found between the sugarcane varieties.3. Ultrastructural observation results show that, under low temperature stress, the root cells were deformed with nuclei retraction and disintegration; root mitochondrial structure was obscure, the membrane was broken or disappeared, the cristae were destroyed and reduced, and the mitochondria began to disintegrate. The destruction of cell and mitochondrial structures was much lesser in the cold resistant variety GT28than the cold sensitive variety ROC22, indicating that the cell and mitochondrial structures are closely related to the cold resistance of sugarcane varieties.4. Under low temperatures stress, the content of superoxide anion radical and the activities of SOD, POD and CAT increased in the mitochondria of sugarcane roots, but the activities of SOD, POD and CAT were lower in ROC22than in GT28, which might result in higher content of superoxide anion radicals in ROC22, leading to heavier membrane lipid peroxidation, earlier aging of mitochondria and speeding cell death.5. The results of SCOT analysis showed that low temperature induced increase or silencing of gene expression in sugarcane roots. Among them, three showed high similarity to a different sorghum hypothetical protein while two others had very high homology with the M. grisea hypothetical protein and BAC clone gene51L01from sugarcane hybrid R570. These genes might be closely related to the cold resistance of sugarcane, but their functions need to be further identified.