Molecular Mechanisms Of Sugar Metabolic And ABA Signal Transduction Key Genes In Regulating Peach Fruit Ripening

The fruit ripening is regulated by a variety of factors,including sugars,plant hormones,and transcription factors.Sugar is an important substance for the formation of sweetness in fruits.It is also involved in the regulation of hormones such as ABA during fruit ripening.At present,there is still a lack of sufficient understanding of the sugar anabolic pathway during peach fruit maturation;the plant hormone ABA is involved in regulating the ripening of climacteric and non-climacteric fruits,but the specific role of ABA in the ripening process of climacteric fruits is still unclear;cold storage is a technique that can extend the postharvest life,it is widely used in fruit and vegetable crops,but peach fruits will suffer from cold damage during long-term low temperature storage,and long-term low temperature induces the production of ABA,(basic leucine zipper,b ZIP)Transcription factor,which plays an important role downstream of the ABA signaling pathway,participates in abiotic stress response.So far,the molecular regulatory mechanism of b ZIP transcription factor in peach fruit on cold damage response is not clear.This study explored the roles of sugar metabolism,ABA signal transduction,and b ZIP family genes in the process of peach fruit ripening and cold damage.The main results are as follows:1.The changes of sucrose,glucose,sorbitol and fructose in peach fruits are clarified during the ripening process,and 13 key genes involved in sugar metabolism are discovered.In this study,the sugar content of Prunus persica was determined by high-pressure liquid chromatography(HPLC)during the six developmental stages of peach(Prunus persica).There are variations in sugar content during fruit ripening.Sucrose increases first and then decreases;glucose and fructose decrease first and then increase,while sorbitol continues to decrease.The transcriptional profiles of a total of 30 genes of key enzymes and transporter proteins for sucrose metabolism,resynthesis and transport were further analyzed.Among them,sucrose phosphatase enzyme(Pp SPS4 and Pp SPS2),hexokinase(Pp HK1 and Pp HK3),neutral/natural converting enzyme(Pp NINV1 and Pp NINV2),vacuole acid converting enzyme(Pp VAINV2),sucrose transporter(Pp SPS4 and Pp SPS2),glucose transporter(Pp HK1 and Pp HK3),(Pp VGT3)and vacuole membrane monosaccharide transporter(Pp TMT1 and Pp TMT2)total13 predictive genes were highly expressed during the maturation of peach fruits,and Pp SPS4 was found to be positively correlated with glucose and fructose.It is speculated that due to the upregulation of Pp SPS4 and Pp SPS2,sucrose accumulates in the cytoplasm.Sucrose transported into the vacuole through the upregulation of Pp SUT2,Pp VGT1,Pp VGT2,Pp VGT3,Pp TMT1 and Pp TMT2 transporter,and the cleavage of sucrose is completed by the upregulated expression of Pp VAINV2.Therefore,as the peach fruit ripe,the sucrose content decreases.During the fruit maturation period(S4 II ? S4 III),the concentration of glucose and fructose increases.This research will improve our understanding of genes related to sugar metabolism in peach fruits and lay the foundation for further exploring the functions of these genes and improving the quality of peach fruits.2.The changes of ABA and ethylene during the ripening of peach fruits were clarified,and two ABA signal transduction genes that may be involved in regulating fruit ripening were discovered.In this study,the ABA and ethylene content of the solute peach ‘Zhongyoutao 13' during fruit ripening were tested,and it was found that both ABA and ethylene were positively correlated with fruit ripening.In the S3 and S4 III phases,the ABA content reached its peak.In addition,the expression of Pp NCED2 and Pp NCED3 genes,key enzymes in ABA biosynthesis,has the same trend as ABA accumulation.Both ABA and ethylene levels peak in the late stage of fruit ripening.These results show that ABA not only initiates the fruit ripening process,but also had accumulated accompany with ethylene in the later stage of fruit ripening.Using bioinformatic identification of the ABA signal path 7 Pp PYL(an ABA receptor),10 Pp PP2C(type 2C protein phosphatase),as well as 7 Pp Sn RK2(subfamily 2 of SNF1-related kinases)gene,and further in RT-q PCR analysis,24 genes expressed during fruit ripening.The expression of Pp PP2C10(PRUPE?ppa005286mg)and Pp Sn RK2.6(PRUPE?ppa006108mg)increased together with ABA accumulation.Yeast two-hybrid and bimolecular fluorescence complementation experiments revealed the presence of mutual work of these two genes.It is speculated that Pp PP2C10 and Pp Sn RK2.6 play a key regulatory role in ABA signaling during peach fruit ripening.3.The changes of ABA and ethylene in peach fruits during low-temperature storage were clarified,47 peach b ZIP transcription factor family genes were identified,and 2 b ZIP transcription factors that may be involved in fruit cold damage were identified through expression profiles.In this study,the solute peach ‘Zhongyoutao 13' was used as the test material and cold storage at low temperature(4°C).It was found that long-term low-temperature storage induced the production of ethylene,the hardness of the pulp decreased,and the low temperature also induced ABA accumulation.Since the basic leucine zipper(b ZIP)transcription factor is involved in the regulation of downstream pathways of ABA signals,47 Ppb ZIP genes were identified through bioinformatics analysis in this study.Further based on RT-q PCR analysis,18 Ppb ZIP genes were discovered to be expressed in refrigerated peach fruits.Among them,Ppb ZIP23 and Ppb ZIP25 were significantly reduced during the refrigeration process,which may be involved in the cold damage of peach fruits.Further analysis of the promoter of the two genes found that this region contains the MYC/MYB/ABRES binding element,but not the DRES/CBFS element,indicating that Ppb ZIP23 and Ppb ZIP25 gene expression may be regulated by the ABA-dependent cold induction pathway,thereby responding to cold damage in peach fruit.