Histone Deacetylases Are Involved In The Regulation Of Sexual Behavior Of Phytophthora Infestans

Potato late blight caused by Phytophthora infestans,is one of the most devastating diseases on potato.The outbreak of this disease has resulted in the death of millions of people in the Irish potato famine occurred in the 19th century.P.infestans is a heterothallic oomycete,which commonly requires two opposite mating types,A1 and A2 to complete sexual reproduction by producing oospores.Oospores play a crucial role in the epidemiology of potato late blight by surviving in soil and serving as the primary inoculum in the following seasons.The gene recombination resulted from the sexual reproduction may lead to the appearance of new virulent strains,which will have input in difficulty for disease management.Recently,the frequent presence of self-fertile isolates in many potato producing areas indicated that the genetic structure of P.infestans population is more complex than before.Base on the facts that the inheritance of the mating type doesn’t follow the Mandelian ratios and the sexual reproduction of Phytophthora is hormonal regulated,we proposed a hypothesis that the genes encoding the production and the reception of hormones α1 and α2 are co-exist in each genome of heterothallic P.infestans isolate,and the expression of these genes are regulated by epigenetic mechanism.To test the above hypothesis,we first investigated the candidate genes in regulating histone acetylation in ten oomycete genomes through bioinformatics approaches and identified a group of diverse histone acetyltransferases(HATs)and histone deacetylases(HDACs)along with three putative novel HATs.We found that the abundance of HATs and HDACs in each species doesn’t related to the total gene content of each species,but related to the outcome of gene duplication and gene loss events in these genes in the evolution of each species,and the habitat of the species.These results suggested that living habitat probably is an important driven force shaping the evolution of these genes.Moreover,gene expression analysis unveiled the specific expression patterns of HATs and HDACs of P.infestans during the stages of development,infection and stress response.Then,we investigated the effect of HDACs on sexual reproduction of P.infestans through treating the wild isolates with HDACs inhibitor TSA,and manipulate the HDACs expression using gene silencing and gene over-expression techniques.We found that under suitable concentrations the A1 self-fertile isolates could form more oospores in medium and the HDACs-,HDAC4-and HDAC7-silenced transformants of the wild-type A1 isolate MX5-1 could form oospores in single culture.Furthermore,we investigated the hormone production and reception and found that these transformants not only retained the abilities of hormone al production and a2 reception as well as the wild type isolate,but also gain the abilities of hormone α2 production and al reception.The type of hormone produced and received by the HDACs-,HDAC4-and HDAC7-over-expression transformants were same as the wild type.These results support our proposed hypothesis.Our study provides useful inputs to help explore the mechanisms of sexual reproduction and the regulation of hormone production and reception,and future studies of the epigenetic mechanism in oomycetes.