| Volvariella volvacea is a saprophytic fungus grown in the tropics and subtropics area with nutritional and medicinal value. V. volvacea can not be stored at low temperature. When it is stored at4℃, its mycelia will autolyze quickly and the fruit bodies will become waterlogged and perish easily. Therefore, from the molecular level to investigate the V. volvacea low-temperature mechanism of autolysis,it will provide a theoretical basis for preservation of mushrooms low temperature, low temperature cultivation and strains cryopreservation.The whole genome of V. volvacea sequencing has been completed.Usually the screening of its low temperature induced genes is used by a differential display technique,but this technique can only be isolated from the limited differences in gene fragments. In this study,We performed Volvariella volvacea strain V23and VH3transcriptome expression profiling with digital gene expression profiling of DNA sepuencing technology, the mycelia samples were treated at0℃for0,2,4h respectively. We analyzed the expression data by bioinformatics techniques:1Analysis of highly expressed genes in the strains within the pairwise comparison;2Analysis of differentially expressed genes involved in metabolic pathways;3Analysis of gene expression in cold-related metabolic pathway;4Analysis of gene expression in cold-related metabolic pathway with FQ-PCR. The results showed that:1The top50highly expressed genes were selected in the strain V23and VH3,Most of the highly expressed genes in the low temperature treatment group and the control group with pairwise comparison,33and34genes appear in the strain V23and VH3respectively.These genes may maintain normal physiological function of V. volvacea and be not induced by low temperature.2Differentially expressed genes were a servies of genes which the ratio between the copy number of the control group and the low temperature treatment group is greater than 15and P<0.01.Five resistance-related genes were found in strain V23of differentially expressed genes,including a cold-induced gene involved in spholipid synthesis metabolic pathway. four resistance-related genes were observed in strain VH3of differentially expressed genes,including three cold-induced gene involved in glycogen, trehalose and mannitol synthesis and degradation pathway.3Analysis of gene expression in phospholipid synthesis pathway,we found that most gene of strain VH3increased,however these genes decreased in strain V23.the phospholipid is an important component of the membrane and phospholipid synthesis was induced by low temperature in the strain VH3,Phospholipid synthesis highly under the low temperature in order to strong cell membrane stability.However the strain V23did not make the appropriate changes which led to autolysis.4Gene expression involve in glycogen and trehalose synthesis and degradation pathways was analysised,the gene of both strain V23and VH3increased highly. The gene expression of strain VH3increased more than strain V23.but glycogen and trehalose degradation related gene expression levels also increased in strain V23,which was opposite in the strain VH3.Higher synthesis of glycogen and trehalose in strain VH3may contribute to better cold tolerance.5Three key genes expressed in the above three pathways was studied with FQ-PCR.The result showed that expression profiling data is consistency and the data indicated that the strain VH3showed excellent characteristics in response to cold-stress.6Two key genes expression of the unsaturated fatty acid metabolic pathway were measured,The results showed that the two gene expression levels decreased in both strains.However the strain VH3decreased less than the strain V23. the ability of unsaturated fatty acid synthesis is decreased in V. volvace which may be one reason of autolysis.By analysis of temperature gene expression profile,we suggested that the related of metabolic pathways and cold tolerance,and hope to lay good foundation for assigning a role for the gene in the low temperature autolyzation phenomenon. |
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