| Navel orange (Citrus sinensis Osbeck) is one of main commercial citrus varieties in China, favored with its very juicy, tasty and richen in Vitamin C. However, due to its overlapping maturation times, it's hard to fully satisfy the market demands on navel oranges in the whole year. And in this case, navel oranges are more depended on a proper storage environment to keep postharvest quality and prolong shelf life of fruit. Under postharvest storage, the orange fruits are prone to losing water, rind staining, and getting other pathological and physiological disorders especially traditional low temperature which may result in numerous cellular and metabolic dysfunctions, such as altered respiration rates, impaired photosynthetic activity, and changes in membrane permeability then subsequently cause serious commercial losses. Thus, Knowledge of fruit morphology, physiology and biochemistry is a prerequisite for thorough understanding of postharvest science. In present study, various navel oranges are stored in the commercial cold rooms at 5℃and put them into 12℃for four days and 20℃for two days before getting them out. After RNA extraction, the expression patterns of differently expressed genes were measured by Genechip technology. After that, we use navel oranges grown in Gannan, China as samplings and store them at the same storage environment then confirm expression of several genes related with postharvest storage by Real-time PCR. The main results are as follows:1. In general, the significantly differentially expressed gene occurred on the first 27 days after storage and the gene numbers in peels are many over than numbers in vesicles. It is probably that peels are exposure on the storage environment directly and would be more sensitive to the change of environment.2. According to the Genechip analysis, the differentially expressed genes are distributed into various plant metabolic pathways, such as plant hormone, transcriptional regulate, carbohydrate metabolism, lipid metabolism, pathogenesis-related protein and other transport or synthesis pathyways.3. During the process of storage, plant hormone genes are changed a lot, including ACC synthase, ACC oxidase, ethylene response factor 1,2 (ERF 1,2), ethylene insensitive 4 participated in the ethylene biosynthesis or catabolism; 9-cis-epoxycarotenoid dioxygenase3 (NCED3) of the ABA biosynthesis; a key enzyme ent-kaurenoic acid hydroxylase 1(KAO1) in GA3 biosynthesis, and 12-oxophytodienoate reductase 2 (OPR2), jasmonic acid carboxyl methyltransferase (JMT), jasmonate resistant 1 (JAR1) in the biosynthesis and signal transduction of JA. Most of these hormones encoded probe sets are down regulated during the storge, only ent-kaurenoic acid hydroxylase 1(KAO1) up regulated which may suggest that the GA3 are increased during the storage.4. Global transcripts profiling analysis revealed that exposure to storage environment markedly affected the expression patterns of many transcription factor genes, including Heat shock protein, WRKY, MYB, NAC, BZIP, BHLH, AP2/ERF et al. These transcription factors play various roles on different pathways. Even if they are from the same family, their expression pattens changed varied with different family members which may related to the self-regulation model or they just take part in different pathways.5. Under stress storage environment, genes encoded enzymes involved in carbohydrate metabolism regulate the balance between biosynthesis and breakdown and transverse among starch, sucrose, glucose and fructose. Simultaneously, genes involved in the process of glycolysis and fermentation, gluconeogenesis, and sugar transport are also differentially expressed, which maintain the cellular metabolism.6. Altered genes encoded esterase, fatty acid dehydrogenase, lipase, lipid transfer protein, phospholipids and etc. are mainly in the peels, while lipid related genes changes little in vesicles and differed with ones in peels, which indicates that lipid metabolism participate the cellular energetic metabolism and membrane lipid modification, subsequently change the membrane permeability, in order to help orange fruits are adaptive to storage environment.7. Although there is no obvious rind staining on the peel, transcripts encoded pathogenesis-related protein also change a lot under orange storage environment, which indicates that the storage itself activate pathogenesis-related gene express, including increased transcripts encoded chitinases and wound responsive protein, while suppressed the expression ofβ-1,3-glucanase and other pathogenesis-relate transcripts.8. The confirmed results by Real-time PCR show that pure low temperature storage increase many gene expression while these genes are down regulated by the Genechip analysis, which partially indicate that down regulated of these genes are resulted from the graded increased temperature before these samples are exposed onto the room temperature. From the results, we could deduce that alternate-temperature storage could alleviate the chilling injury, especially the fruit quality decrease because of the temperature increase suddenly.
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