| Sweet sorghum is a type of grain sorghum. Lower cost of investment and higher benefits of economics made great development prospects. In order to reveal the accumulation mechanism of sucrose in the stem and leaf of sweet sorghum mutants, KF1210-3 and KF1210-4 were selected from control which were irradiated by carbon ion irradiation. The dynamic changes of sucrose, fructose, glucose contents, sucrose metabolism related enzyme activity, as well as the genes expression of the related metabolism enzyme were investigated. The results and conclusions were listed as following:1. During early development of both mutants and control, sucrose was decomposed into hexose by metabolizing enzymes for organism growth and development, During the mature period, sucrose was the main accumulation material and the stem mainly performed storage organization in mutants and control. Furthermore, the content of sucrose was remarkably increased between KF1210-3 and KF1210-4 compared to control at mature stage and 1.34, 1.23 times of control, Respectively. Therefore, carbon ion irradiation technology played a certain promoting role in increasing sucrose content of sweet sorghum.2. The sugar accumulation in KF1210-3, KF1210-4 was the result of synergistic effects which involved in SPS, SSs, SSc, INVN and INVA. During seedling stage, the ability to sucrose decomposition which was used for supply in mutants was higher than control in the stem. At mature stage, the ability of decomposed sucrose was gradually slow down and became lower than control. These physiological and biochemical changes were accompanyed with significant increase of SPS and SSs activity, as well as increased intensity of sucrose decomposition by INVN and INVA in leaf.3. As for control, the content of sucrose had no obvious correlation with INVA in the stem of control, While there was a significant positive correlation between sucrose content and the activity of SPS, SSs, SSc, INVN. However, for KF1210-3, KF1210-4, there was no significant correlation between sucrose content and INVN, SSc. While there was extremely significant negative correlation with INVA, and significantly positive correlation with SSc, and positively correlated with SPS. In leaves, the correlation between SPS, SSs, SSc, INVN, INVA activity and sucrose content in KF1210-3, KF1210-4 was higher than in control. Especially, the correlation of KF1210-3 was higher than that of KF1210-4. All these led to a higher level for sugar synthesis and store in KF1210-3 than KF1210-4.4. During the seedling stage, the expression level of INV3 in the stem of KF1210-3 was the most highest, which was accordance to the vigorous sucrose decomposition, so as to ensure more hexose involved in the plant metabolism. In booting and mature stage, the expression level of INV3 expression level was very low, accompanied with a rapid decrease of sucrose decomposition, which contributing to the rapid accumulation of sucrose. Compared to INV2, INV3 mainly played a roled in the regulation of sucrose metabolism, while INV2 only in the mature period.5. The SPS2, SPS3 expression levels to enzyme activities becomes difficult since oligomerization or phosphorylation of the gene products are known to give rise to functional enzymes, and the SPS2, SPS3 expression levels is related to the result of synergy by the other SPS regulatory genes, resulting in lower levels of expression in the final stage.6. In the early growth stage, SUS1 and SPS gene promote the sucrose synthesis in the stem and leaf. However, at the mature stage, SUS1 mainly controlled the decomposition of sucrose synthase, and lower than control(KF1210-3 minimum). Compared with SUS1, SUS2 was mainly controlled in the regulation of sucrose metabolism.In brief, carbon-ion irradiation was effective to induce mutations with increasing sugar content in sweet sorghum. Higher sucrose synthesis ability and lower decomposition behavior led to the increase of the sucrose content in KF1210-3 and KF1210-4. |
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