Study On The Differences Of Dimorphic Cells In Tremella Fuciformis

Dimorphism is the capacity displayed by different fungi to grow in the form of yeast or mycelium,depending on the environmental conditions.It has long been believed that phase transition between yeast and mycelium is obligatory for pathogenicity in some dimorphic fungi,so dimorphism of fungi attracts a great deal of attention in recent years. Dimorphic transition is regulated by a variety of extracellular factors including physical factors,chemical factors and nutritional factors,and it is also regulated by intracellular signal transduction pathways such as cAMP-PKA,MAPK and Rim101.In order to reveal the differences among the dimorphic cells,basidiospores,arthrospores and mycelia of Tremella fuciformis were used to study the effects of different environmental factors and were subjected to microscopical observation,electrophoresis analysis and RNA arbitrarily primed PCR(RAP-PCR).The result of morphology observation shows that basidiospores and arthrospores can bud to produce yeast-like cells,the compatible cells produced germination tube and conjugated to produce mycelium with clamp connection when were grown together. Pseudohyphal form and hyphal form is also be found in basidiospores and arthrospores. The result of the effects of seven environmental factors,which include carbon source, nitrogen source,C/N ratio,pH value,culture temperature,culture time and the supernatant of Hypoxylon xianghui shows that all of the environmental factors have influence on the dimorphic transition between yeast form and mycelium form.The extracellular supernatant of Hypoxylon xianghui sterilized by filtration was best for the growth of mycelium form in liquid media,the ratio of mycelium form in arthrospores was high at 9.89%and in basidiospores was high at 9.47%.In general,the effect of C/N ratio is lower than other factors and the ratio of mycelium form was less than 2.4%under the given C/N ratios.All the factors have different behaviors in the solid or liquid media. The whole protein and isozyme analysis indicated that the mycelial form contains more bands than that of yeast form and some differences in peroxidase and esterase between the two forms were found,while the polyphenol oxidase are almost similar.Total RNA were extracted and purifeied from yeast form and mycelium respectively.The differentially expressed genes between yeast form and mycelium form of Tremella fuciformis were studied by RAP-PCR.The differential displayed fragments named Seq2 and Seq1 were cloned and sequenced.Seq1 was found to similar with hypothetical protein of Cryptococcus neoformans var.neoformans and in gene level,and Seq2 was also found to similar with hypothetical protein of Aspergillus clavatus in gene level.