The Physiological And Biochemical Characteristics Of Transgenic Sugarcane With SoSUT5 Gene

Sugarcane is the most important sugar crop,and cane sugar accounts for about 75%of total sugar production in the world,while more than 90%in China.Sugarcane production is determinate to the sugar security in China.The sucrose produced by photosynthesis of sugarcane transports from the source tissue to the sink tissue,which requires the transport of sucrose transporter(SUT).SUT plays an important role in the storage,transport,metabolism and other physiological processes of sucrose.In this experiment,six SoSUT5 transgenic sugarcane lines(T1,T2,T3,T6,T9,and T11)and a control(WT)were used as materials,and grown in greenhouse.The aims were to investigate the agronomic traits,sucrose metabolism-related enzyme activities,internode sugars and SoSUT5 expression in the plants at the seedling stage,tillering stage,elongation stage and processing maturation stage,respectively,to provide the necessary research basis and reference for exploring the function of SoSUT5.The main findings are as follows.1.This study validated that all the lines are transgenic by multiplex PCR and herbicide resistance screening.The marker gene bar was amplified by PCR and sequenced.The results showed that all the six sugarcane lines were transgenic.The recombinant fragments consisting of the plant expression vector and the exogenous gene SoSUT5 were amplified by PCR,and the results again showed that the six sugarcane lines were transgenic.In herbicide resistance screening,all the six sugarcane lines showed certain herbicide resistance and further proved the phenotypes are transgenic.2.The investigation on the agronomic traits in sugarcane revealed that,except for T6,the plant height and stalk diameter were improved in the transgenic sugarcane lines compared with the WT,and the differences were increased with the plant growth process.And the plant height differences between WT and T1,T2 reached the significant level,and the stalk diameter difference between WT and T6 reached the highly significant level.The relative content of chlorophyll and leaf area were higher in T6 than WT,and the differences increased with the growth process.The cane Brix was also higher in the transgenic lines,and T9 and T11 showed highlyly significant differences from WT.3.The activities of sucrose metabolism-related enzymes in sugarcane+1 leaf were measured at various growth stages.The results indicated that the activity of SPS showed an increasing trend,while the activity of SSs showed a decreasing trend from the seedling stage to the processing maturation stage,which might suggest that the SPS was the main enzyme for sugar accumulation during sugarcane maturing.SSs mainly played a role in catalytic synthesis at the seedling stage,tillering stage,and elongation stage.SSs showed the lowest activity at the processing maturation stage,which suggested that this enzyme may be mainly related to the plant growth.The activities of SPS and SSs were all higher in the transgenic lines than the WT,and the lines T9 and T11 were significantly different from the WT.The SSc activity showed an increasing trend from the seedling stage to the elongation stage,while decreasing from the elongation stage to the processing maturation stage in all the transgenic lines and WT,and it was the lowest at the seedling stage and the highest at the elongation stage.At the four growth stages of sugarcane,the AINV activity was higher in the "WT than the transgenic lines,which differences were significant,but there was no significant difference among the transgenic lines.The activity of NINV gradually increased from the seedling stage to the elongation stage,and then gradually decreased to the mature stage.It seems that the NINV plays a catalytic role in the tillering and elongation stages.It had the lowest activity at the seedling stage and the strongest at the elongation stage.The NINV catalyzes sucrose decomposition into hexoses that may be used for the elongation of sugarcane internodes.The SSc activity was lower in the transgenic lines than the WT at each stage,and that in T2,T3,T9,and T11 showed significant differences from the WT at the four stages.4.At processing maturation stage,fructose and glucose contents in sugarcane internodes were almost equal.Total reducing sugar content was low while sucrose content was high.In the transgenic sugarcane line,the fructose and glucose contents of T11 were significantly higher than that of the WT,and the remaining sugar content was lower in the other lines than the WT.The sucrose and total soluble sugar contents were slightly lower in transgenic sugarcane line than the WT.The expression level of SoSUT5 was higher in the transgenic lines than the WT.