Study On The Mechanism Of Resistance Against Oxidative Stress In Candida Albicans By Array CGH

The incidence of systemic fungal infection that caused by Candida albicans has been risen dramatically in recent year. How to reduce Candida albicans infection becomes more urgently. The major reasons of the occurred infection is Candida albicans can responses to oxidative stress that produced by host immune system, moreover, it can resistance against oxidative stress. Study on the mechanism of resistance against oxidative stress in the level of genome that causes resistance oxidative stress, will help to depress the occurrence of Candida albicans infection.Objective:In this subject, we choose the Candida albicans that exist a significant difference in oxidative stress tolerance as the research object, study on these Candida albicans features of the genome, aim to explain the mechanism of the Candida albicans resistance against oxidative stress in genomic level, look for the key genomic regions and the key gene that relate to resistance against oxidative stress .Methods:In the first part of this study, Use hydrogen peroxide to simulate oxidative stress, We undertake Hydrogen peroxide tolerance test, Choose the strains that differences in oxidative stress tolerance from clinical Candida albicans strain library. Then, confirmed the differences through Spot array, Survival rate test, Time growth curve and so on, Finally, We identified three strains of resistant against oxidative stress, and three strains of sensitive to oxidative stress.In the second part of this study, We use the genome oligo nucleotide microarray of Candida albicans to carry out array comparative genomic hybridization, Confirm the result of chip hybridization by Real-time PCR, Apply of cluster analysis on the chip hybridization results. We locate the information of copy number variations from the chip hybridization in the chromosome of Candida albicans through the Cluster-Miner software. Use the SAM statistical analysis, screening the genes that is closely related to oxidative stress tolerance. Analysis the function of the differences genes through the Candida Genome Database.Results:The results of cluster analysis display that the different oxidative stress tolerance of Candida albicans belong to different clusters, three strains of resistant against oxidative stress are a cluster, and three strains of sensitive to oxidative stress are a cluster. We screened the genes that is closely related to oxidative stress tolerance through SAM statistical analysis, Finally received 122 copies of gene differences,Based on copy number variations in genomic information clustering results of different traits, we thought that the Candida albicans resistance against oxidative stress with some certain genome features.The result obtained from the locate the information of copy number variations in each chromosome of Candida albicans. and combined with real-time quantitative PCR validation and bioinformatics analysis, we confirm two domains that are relate to the Candida albicans resistant against oxidative stress. One region is on the chromosome R of Candida albicans, This region of Oxidative stress-sensitive strains are missed, and the oxidative stress-tolerance strains in this region are no change or amplified. The other region is on the 4th chromosome of C. albicans with a length of around 31kb region, In the Oxidative stress-tolerance strains, this region is missed, and in Oxidative stress-sensitive strains, this region is not changed. This prompted that these regions are likely relate to resistance against oxidative stress in Candida albicans.Conclusions:We obtained the information of the Candida albicans gene copy number variations through the Array comparative genomic hybridization, and relate these information to the character of Candida albicans resistant against oxidative stress. Discovered two important chromosomal variation section that relate to resistance against oxidative stress in Candida albicans. Through analysis the gene function, we concluded the mechanism of Candida albicans resistance against oxidative stress: Candida albicans chromosome R, There are many genes that closely relate to amino acid synthesis, the region deletion can cause that Candida albicans can not positive response to external stimuli including oxidative stress, and thus can not be tolerated. Candida albicans chromosome 4, there is a retrotransposons, and its existence can cause genome instability, and thus should not tolerate oxidative stress.These Conclusions provide a lot of new ideas for the study on the mechanism of resistance against oxidative stress in Candida albicans...