Effect Of Overexpression Of StTZF5 And StAP2a On Storage Quality Of Potato

Potato(Solanum tuberosum L.)is the fourth largest food crop in the world and plays an critical role in ensuring food security and promoting economic development.Potato consumption demand is moving from traditional mode to post-harvest processing industry(such as French fries,potato chips).In order to extend the processing cycle and suppress the loss caused by reduce sprouting,water loss,disease spread,tubers always storage at low temperature(< 10 ℃).But it resulted in imbalance of starch metabolism,an accumulation of reducing sugars(RS)which is known as cold-induced sweetening(CIS).Maillard reaction occurs between RS and free amino acids during frying,resulting in discoloration of the product and simultaneous generation of acrylamide,which negatively affects product quality and human health.In previous research,the mechanism of CIS mainly focused on the functions of key enzyme genes in starch-glucose metabolism,such as AGPase1 which regulates starch synthesis,and Stvac INV1 which regulate sucrose hydrolysis and the starch hydrolase StBAM9.However,their transcriptional regulatory mechanisms remains unclear.We analyzed the expression patterns of transcription factors(TFs)during cold storage to select possible candidate transcription factors.This study selected two genes,StAP2 a and StTZF5,to further analyze their functions and regulatory mechanisms in CIS.The main results are as following:1.Cloning and analysis of StAP2 a and StTZF5 in potatoThe StAP2 a gene CDS is 1428 bp in length and encodes 475 amino acids.It contains the AP2 / ERF domain at positions 137-198 and 228-291,respectively.Multiple sequence alignment and dendrogram analysis found that StAP2 a belongs to the AP2-like domain,the eu AP2 lineage subfamily.StAP2 a has nuclear localization signals,transcriptional activation in yeast and transcriptional activation activity in tobacco.The StTZF5 gene CDS is 1428 bp in length and encodes 427 amino acids.It contains two zinc finger protein domains at amino acids 133-159 and 168-191,respectively.The type of zinc finger protein belongs to C-X7-C-X5-C-X3-H.The bioinformatics analysis found that the StTZF5 belongs to the C3 H zinc finger protein family subfamilyⅠ.StTZF5 has nuclear localization signals,transcriptional activation in yeast,and transcriptional activation activity in tobacco.2.Analysis of StAP2 a and StTZF5 gene function and regulatory mechanism in potato.In order to study the function of StAP2 a and StTZF5 in CIS.The overexpression vectors p JCV55-AP2,p JCV55-C3 H were constructed and transformed into CIS-sensitive genotype E3.The transgenic lines and the control E3 were planted in a greenhouse and the harvested tubers were stored at low temperature,and their physiological and biochemical indexes were analyzed.The results showed that after storage at low temperature of 4 ℃,the overexpression of StAP2 a transgenic lines significantly increased reducing sugar content,accelerated starch degradation,deepened browning degree of fried chips and increased amylase activity,Invertase activity is significantly reduced.Overexpression of StAP2 a increased the expression level of StBAM9 gene and decreased the expression level of INV1 and StTPS.However,under room temperature storage,the content of reducing sugar,sucrose and did not change significantly.Under low temperature storage,the transgenic lines overexpression of the StTZF5 gene significantly increased reducing sugar content,starch degradation rate,deepening the color of fried chips.Amylase activity increased and invertase activity decreased,the expression of StBAM9,INH2 increased significantly and SPS and StTPS decreased.There are no significant change in the reducing sugar,sucrose content under room temperature storage.In summary,the StAP2 a belongs to the AP2-like gene family and the StTZF5 belongs to the C3 H gene family.StAP2 a and StTZF5 increase the amylase activity by increase the expression of StBAM9 at low temperatures,thereby accelerating the degradation of starch and promoting the accumulation of reducing sugars,and on the other hand,inhibiting the expression of StTPS,which may indirectly regulate starch through T6 P signaling sugar metabolism to affect the CIS.