Study On Species Diversity And Differentiation Of Trichoderma In Aquatic Plants

Trichoderma Pers.(Ascomycota,Sordariomycetes,Hypocreales,teleomorph Hypocrea Fr.),often existing in agricultural fields,surface on twig and as endophyte in plant tissue,it is widely used in productions of agriculture and industry because of it can produce chitinases,cellulolytic enzymes,also possess antagonistic abilities by secretion of antibiotics.More than 300 species have been reported so far,most are isolated from soil,rotten woods and several species were collected from terrestrial plants.But it has no report form aquatic endophyte.Our study initially explore the conditions that new species high frequently occur in the special habitat on the basis of searching for aquatic endophyte Trichoderma diversity in southwestern area,specifically for carbon source spectrum,photoinhibition,mating type gene and genome,we compared the differences among T.aquatica,T.reesei and T.parareesei in above respects.The main results are as follows:1.We only obtain 23 Trichoderma strains from about two thousand strains,combine the analysis of morphology and base on the internal transcribed spacer(ITS)regions of the ribosomal DNA,the translation elongation factor 1-? encoding gene(TEF1)and the gene encoding the second largest nuclear RNA polymerase subunit(RPB2),eight known species were obtained:T.atroviride,T.citrinoviride,T.harzianum,T.longibrachiatum,T.orientate,T.paraviridescens,T.spirale,T.tomentosum;eight new species were identified,named as T.aquatica,T.pseudoasperelloides,T.paraviride,T.asymmetricum,T.inconspicuum,T.uncinatum,T.scorpioideum and T.tibetica.Among them that possess cellulolytic ability such as T.longibrachiatum,T.aquatica,T.citrinoviride accounted for about one third.2.The mating type genes of two T.aquatica strains are MAT1-1,we initially speculated that reproductive pattern of T.aquatica are asexual reproduction due to a few samples.On MAT1-1-1 locus,there are only two amino acid sites mutation in T.aquatica.3.We used Biolog FF MicroPlates to examine utilization condition of T.aquatica KS70 and KS76 for 94 substrate,KS70 and KS76 can make good use of 38 carbon sources and 66 carbon sources respectively,T.reesei and T.parareesei can make good use of 66 carbon sources and 63 carbon sources respectively,the number and species of carbon sources are more than that of KS70,and there are some differences with KS76 for utilization condition of part carbon sources.We also furtherly examined the effects of illumination on growth of two strains on 28 ? and compared with 40 carbon sources reported previously.The results indicate that there were 80 photoinhibition cases and 68 photoinhibition cases in KS70 and KS76 respectively.For the 40 carbon sources that most suitable for growth of T.reesei and T.parareesei reported previously,there were 34 photoinhibition cases and 30 photoinhibition cases examined in KS70 and KS76,by contrast,there were only 11 photoinhibition cases and 1 photoinhibition case in T.reesei and T.parareesei,which suggest that photoinhibition cases frequently occur in T.aquatica.The result indicates that the change of habitat leads differences of carbon sources utilization condition between T.aquatica and relative species,which may lead to species differentiation.4.The genome size of T.aquatica is 34 Mb,52%of which is repeat sequences.GC content is 59.2%,slightly higher than other species in the genus,but the gene number is the fewest,about 7500.Up to 69.7%lost during evolution.T.aquatica,T.reesei and T.parareesei share 6959 core genes,specific genes number for T.aquatica only are only 54.There are 331 genes including six CAZyme of T.aquatica,among them the number of Glycoside Hydrolases genes are 197,accounting for 2.63%in all genes,is the most proportions among CAZymes,yet that of T.reesei only accounting for 1.9%,other secondary metabolism-related genes all hold a large proportions,which suggest T.aquatica possesses certain ability to mycoparasitic,the ability is related to its living environments.However,it is necessary to need more evidence to verify that the interior of aquatic plant is a factor which results in species differentiation.