Physiological Responses Of Different Tolerance Of Tomato And Expression Analysis Of Related MiRNA Under Phosphorus Stress

Phosphate is one of inorganic nutrients required by plants. Soil phosphorus mainly exists at fixed and organic state which can not be absorbed by plants. Therefore, phosphorus stress is common in plant. Tomato has wide varieties rich nutrient, high yield and good market, so it becomes one of the main vegetables in china. Phosphorus deficiency makes plant small, stunted growth, seriously affecting tomato yield and quality. As a new small molecule RNA, miRNA regulates expression of target gene and plays an important role in low phosphorus signal transduction and phosphorus balance.There were many studies found that multiple miRNA involved response of phosphorus stress in plant. The diversity of miRNA target genes determines the complexity of miRNA signaling pathways. The change of soluble sugar content is important metabolic pathways of plant response to phosphorus deficiency under phosphorus starvation in plant. The purpose is clear whether different genotypes of tomato initiate the roots response mechanism to phosphorus deficiency through the changes of carbohydrate metabolism and the expression of main miRNA. In this study, compared the change of carbohydrate content and key enzyme activities in different part of two tomato strains No.9 (tolerance to low phosphorus type) and 30 (P sensitive) under phosphorus stress treatments. Analyze the expression of sucrose transporter SUT and miRNA in different parts of tomatoes with real-time quantitative PCR technical. Discuss molecular mechanism of miRNA and SUT response to low phosphorus stress. The above all are theoretical basis to establish a new line of soil phosphorus efficient crop. Results of this experiment are as follows:(1) After low phosphorus treatment, the root length of the 9 lines was increased by 69.52% compared with the control group, while the root length of the 30 lines was 26.18% lower than that of the control group. From the root to shoot ratio,9 lines significantly increased and 30 lines significantly reduced. The indicators of the 9 lines are better than 30 lines in the fresh weight, the 9 lines have good adaptability in the low phosphorus conditions, the 30 lines is the opposite. The total phosphorus content of the plants showed a downward trend in the two strains of phosphorus uptake. But the decline in 9 line trends below 30, and plant under low phosphorus stress conditions, root shoot ratio and the content of phosphorus is higher tolerance is stronger, so low phosphorus stress P, lines 9 growth trend and patience is better than phosphorus sensitive cultivar 30th.(2) Phosphorus glucose and sucrose were increased under phosphorus deficiency in tomato leaves and stems in 9 lines fructose, while 30 is the opposite. Converting enzyme active reduced in 30 tomato lines with varying degrees, while transit Enzymes major decrease in roots and is higher in stems and leaves in 9. The results show that sucrose transporter SUT different expression significantly within 24 hours under phosphorus treatment, SUT1 expression higher in 9 leaves and stems, and SUT2 expression higher in roots and SUT4 higher expression in leaves. These results suggest that photosynthesis in tomato plants shoots are affected under low phosphorus stress, which lead changes in carbohydrate levels, thereby affect the expression of sucrose transporter protein and sucrose in plant distribution, and ultimately affect the plant response difference to phosphorus deficiency.(3) In this study, analyzed the expression changes of 12 miRNA in two tomato strains under phosphorus Stress-induced. We found different expression when P treatments 24H, we have reached a significant level, While miR 837-3p, miR 862-3p and miR 862-5p testing also found 12H and 24H is a particular point in time. It is speculated that 12H and 24H may be miRNA regulation point time. We also found that compared phosphorus absorption efficiency, the expression in high-sensitive 9 is higher than the 30. It also proved efficient phosphorus absorption more responsive to phosphorus stress. Through experiments we found that miR399 and miR837-3p expression obvious differences, so verified these two miRNA target genes. Correlation analysis show miR837-3p may play an important role in regulating different tomato tolerance under low phosphorus.