Regulation On Mitochondrial And Expression Of Its DNA Polymerase Related To Fruit Quality By Nitric Oxide In Peach Fruit During Cold Storage

Peach?Prunus persica L.?was a kind of typical respiration climacteric fruit,mainly manifested in rapid ripening and senescence after harvest.Low temperature storage was a widely used for fruit storage,but low temperatures greatly caused cold damage,fruit tissue brown stain and flesh flocculation and so on.Moreover,it generated a large amount of ROS,cause oxidative damage and mitochondrial dysfunction in chilled fruits.Nitric oxide?NO?,an important signal molecule involved in the stress response of plants to biotic and abiotic,had a regulatory effect on plant maturation and senescence and alleviates cold damage during storage.Therefore,in this study,‘Xintaihong'peach fruit was used as test material,soaked of 30min in double distilled?control?,15?mol L^-11 NO and 5?mol L^-11 c-PTIO?NO scavenger?.After the end of treatment,the fruits were stored at 0°C.Researched on oxidative damage of mitochondria of cold-stored peach fruit by exogenous NO treatment as well as regulation and repairing function,provides a theoretical basis for relieving chilling damage and improving storage quality of peach fruit from biochemistry's perspective.The main results were as follows:1?During cold storage,compared with CK and c-PTIO,exogenous NO treatment could significantly delay the decrease of firmness and lightness and the increase of soluble solids content,relative conductivity and weight loss.Moreover,NO treatment could effectively reduce the respiratory rate during storage,delay the occurrence of respiratory peaks,at the second respiratory peak was reached,the NO treatment of peach fruit respiration rate was CK and c-PTIO treatments 77%and 52.7%,respectively,could play a better role in keep fresh.It showed that NO treatment could significantly maintain the storage quality of peach fruits during cold storage.2?Exogenous NO treatment could effectively delay the increase of mitochondrial ROS content in cold-stored peach fruits,and reached the maximum value in 4^thh week,the mitochondrial ROS content of NO treatment was only 70.7%of 5?mol L^-11 c-PTIO treatment,indicated that NO could significantly reduce oxidative stress caused by stress.Moreover,NO treatment could significantly inhibit mitochondrial swelling caused by oxidative damage,delay the decrease mitochondrial membrane potential,mitochondrial membrane fluidity and mitochondria respiratory chain complex?C?-C??enzyme activity.The results showed that NO could maintain the integrity of mitochondrial membrane structure and function by inhibit the accumulation of ROS.3?The PpPol?B genes of‘Xintaihong'peach fruits were successfully cloned by RT-PCR technology,and the CDS region sequence was 3201 bp,encoded 1066 amino acids.Bioinformatics analysis of Pol?B protein using online software predicted that the molecular formula of the protein was C₅₂₂₂H₈₂₅₃N₁₄₉₅O₁₆₀₁S₄₄,the relative molecular mass was 11905.67,and the protein was hydrophilic.There was no transmembrane region and signal peptide region.Phylogenetic tree analysis showed that the amino acid sequence of Pol?B protein was highly conserved,with the highest homology to Pol?B of Prunus avium being 97.94%.Recombinant protein constructed in vitro was successfully expressed in Rosetta?DE3?.4?Compared with CK,the exogenous NO could effectively delay the decrease of mtDNA copy number content and maintain the stability of mtDNA level during the cold storage process of peach fruits.The NO treatment could effectively delay the increase of 8-OHdG content and decrease mtDNA polymerase activity.Furthermore,application of c-PTIO treatment could accelerate mtDNA copy number,decrease mtDNA polymerase activity,and increase mitochondrial 8-OHdG content.In base-excision repair pathway,NO treatment could significantly delay the decline of PpOGG1,PpAPE1,PpPol?B and PpLIG1gene expression levels related to the base excision repair pathway,thereby repairing damaged mitochondrial DNA and maintaining stability of mitochondrial function.