Effect Of Mechanical Wounding On Carbohydrate Metabolism In Potato Tubers And Mechanism Of StpGlcT2 Response To Wounding

Mechanical wounding accelerates starch breakdown in plants,which can activate glucose metabolism to provide the carbon skeleton,energy and reducing force for wound healing.In addition,the sugar produced at the wound site must be transported by transporters to be used effectively.It has been reported that mechanical wounding leads to starch degradation,activation of sugar metabolism,and involvement of sugar transporters in model plants that subjected to wound stress.However,how these metabolisms occur in wounded tubers has not been reported.In this study,we selected"Atlantic"potato tubers as material.Based on the analysis of wound effects on potato tuber starch degradation,sugar metabolism and the expression of sugar transporter genes,the sugar transporter Stp Glc T2 was selected as a target gene and verified the function of this gene in response to wound stress was verified by tuber overexpression and interference expression.The results were as follows:1.Mechanical wounding significantly upregulated the expression of starch degradation-related genes St GWD,St AMY,St BAM and St ISA,and promoted the starch degradation at the tuber wound site.Mechanical wounding also significantly upregulated the expression of the sucrose conversion-related genes St SUS,St BG and St St INV,and promoted the accumulation of glucose,fructose and sucrose at the tuber wound site.During starch granule degradation,the hard shell layer on the surface of starch granules is first peeled off,the proportion of the large and medium-sized starch grains increases,and the average particle size increases.2.Mechanical wounding upregulated the expression of genes related to glycolysis and pentose phosphate pathway metabolism St HK,St PFK,enolase and St G6PDH,transketoase,and increased the activity of HK,PFK and G6PDH enzymes.The wound increased the levels of G-6P and the end product PEP of glycolysis at the wound site,and the levels of FDP and the end product E-4P of the pentose phosphate pathway.The wound promoted the conversion of PEP and E4P to shikimic acid and phenylalanine.3.Transcriptional analysis showed that wound significantly up-regulated the expression of eight sugar transporters,of which Stp Glc T2 was the most up-regulated.After constructing potato plants with Stp Glc T2 overexpression and interference expression,it was found that the morphology of the overexpression plants was normal,while the growth and development of the interference expression plants were affected.The overexpressed tubers were wounded,the expression of starch degradation genes was significantly up-regulated,the starch degradation was faster,and soluble sugar content was significantly increased.The starch content in the interfering tubers was significantly lower than that in the wild-type,the soluble sugar content was also lower,the starch degradation genes were almost not expressed after wounding,and the starch degradation almost did not occur.In addition,more suberin was accumulated at the wound site in the overexpressed tubers,whereas less was accumulated in the interference tubers.4.Transcriptome analysis revealed that 972 and 2752 DEGs genes were enriched in the damaged tubers with Stp Glc T2 overexpression.There were significant differences in DEGs involved in starch and sugar metabolism in overexpressed and interfered tubers.The number of up-regulated genes in the starch degradation pathway was higher in overexpressed tubers,while the number of up-regulated genes in the sugar metabolism pathway was higher in interfered tubers.In addition,more Ca²⁺signaling related proteins were significantly upregulated in overexpressed tubers.5.Nine proteins potentially interacting with Stp Glc T2 were obtained by yeast two-hybrid c DNA library screening.Three weakly interacting proteins St NF-YB10,St CML36 and St LTP4 and two strongly interacting proteins St TAS14,St Ca M7 were obtained by yeast two-hybrid verification.Combined with the previous transcriptional analysis and verification,St Ca M7 was finally identified as the interaction target.Bi Fc verification showed that the interaction between Stp Glc T2 and St Ca M7 occurred at the membrane.After truncation of Stp Glc T2,St Ca M7 was found to bind to the 5-7th transmembrane segments of Stp Glc T2.In conclusion,mechanical wounding can accelerate the starch degradation at the wound site of potato tubers,promote the accumulation of soluble sugars,and increase the activity of carbohydrate metabolism and the pentose phosphate pathway.Wounding can also induce the expression of sugar transporters at the wound site,in which Stp Glc T2 plays an important role.After wounding,starch degradation was accelerated in tubers overexpressing Stp Glc T2,whereas the interfering tubers showed little degradation.Stp Glc T2 can also interact with St Ca M7.This study provides a new theory to elucidate the pathway of starch degradation and the mechanism of sugar transport in potato tubers under wound stress.