The genus Cladosporium and similar dematiaceous ... - CBS - KNAW
The genus Cladosporium and similar dematiaceous ... - CBS - KNAW
The genus Cladosporium and similar dematiaceous ... - CBS - KNAW
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Arzanlou et al.<br />
To date 26 species have been named in Ramichloridium; they<br />
not only differ in morphology, but also in life style. Ramichloridium<br />
mackenziei C.K. Campb. & Al-Hedaithy is a serious human<br />
pathogen, causing cerebral phaeohyphomycosis (Al-Hedaithy et al.<br />
1988, Campbell & Al-Hedaithy 1993), whereas R. musae causes<br />
tropical speckle disease on members of the Musaceae (Stahel 1937,<br />
Jones 2000). Another plant-pathogenic species, R. pini de Hoog &<br />
Rahman, causes a needle disease on Pinus contorta (de Hoog et<br />
al. 1983). Other clinically relevant species of Ramichloridium are R.<br />
basitonum de Hoog <strong>and</strong> occasionally R. schulzeri (Sacc.) de Hoog,<br />
while the remaining species tend to be common soil saprobes.<br />
No teleomorph has thus far been linked to species of<br />
Ramichloridium. <strong>The</strong> main question that remains is whether shared<br />
morphology among the species in this <strong>genus</strong> reflects common<br />
ancestry (Seifert 1993, Untereiner & Naveau 1999). To delineate<br />
anamorphic genera adequately, morphology <strong>and</strong> conidial ontogeny<br />
alone are no longer satisfactory (Crous et al. 2006a, b), <strong>and</strong> DNA<br />
data provide additional characters to help delineate species <strong>and</strong><br />
genera (Taylor et al. 2000, Mostert et al. 2006, Zipfel et al. 2006).<br />
<strong>The</strong> aim of the present study was to integrate morphological<br />
<strong>and</strong> cultural features with DNA sequence data to resolve the<br />
species concepts <strong>and</strong> generic limits of the taxa currently placed in<br />
Periconiella, Ramichloridium, Rhinocladiella <strong>and</strong> Veronaea, <strong>and</strong> to<br />
resolve the status of several new cultures that were isolated during<br />
the course of this study.<br />
Materials <strong>and</strong> Methods<br />
Isolates<br />
Species names, substrates, geographical origins <strong>and</strong> GenBank<br />
accession numbers of the isolates included in this study are listed<br />
in Table 1. Fungal isolates are maintained in the culture collection<br />
of the Centraalbureau voor Schimmelcultures (<strong>CBS</strong>) in Utrecht, the<br />
Netherl<strong>and</strong>s.<br />
DNA extraction, amplification <strong>and</strong> sequence analysis<br />
Genomic DNA was extracted from colonies grown on 2 % malt<br />
extract agar (MEA, Difco) (Gams et al. 2007) using the FastDNA kit<br />
(BIO101, Carlsbad, CA, U.S.A.). <strong>The</strong> primers ITS1 <strong>and</strong> ITS4 (White<br />
et al. 1990) were used to amplify the internal transcribed spacer<br />
region (ITS) of the nuclear ribosomal RNA operon, including: the<br />
3’ end of the 18S rRNA gene, the first internal transcribed spacer<br />
region (ITS1), the 5.8S rRNA gene, the second internal transcribed<br />
spacer region (ITS2) <strong>and</strong> the 5’ end of 28S rRNA gene. Part of<br />
the large subunit 28S rRNA (LSU) gene was amplified with primers<br />
LR0R (Rehner & Samuels 1994) <strong>and</strong> LR5 (Vilgalys & Hester 1990).<br />
<strong>The</strong> ITS region was sequenced only for those isolates for which<br />
these data were not available. <strong>The</strong> ITS analyses confirmed the<br />
proposed classification based on LSU analysis for each major<br />
clade <strong>and</strong> are not presented here in detail; but the sequences are<br />
deposited in GenBank where applicable. <strong>The</strong> PCR reaction was<br />
performed in a mixture with 0.5 units Taq polymerase (Bioline,<br />
London, U.K.), 1× PCR buffer, 0.5 mM MgCl 2<br />
, 0.2 mM of each<br />
dNTP, 5 pmol of each primer, approximately 10–15 ng of fungal<br />
genomic DNA, with the total volume adjusted to 25 µL with<br />
sterile water. Reactions were performed on a GeneAmp PCR<br />
System 9700 (Applied Biosystems, Foster City, CA) with cycling<br />
conditions consisting of 5 min at 96 °C for primary denaturation,<br />
followed by 36 cycles at 96 °C (30 s), 52 °C (30 s), <strong>and</strong> 72 °C<br />
(60 s), with a final 7 min extension step at 72 °C to complete the<br />
reaction. <strong>The</strong> amplicons were sequenced using BigDye Terminator<br />
v. 3.1 (Applied Biosystems, Foster City, CA) or DYEnamicET<br />
Terminator (Amersham Biosciences, Freiburg, Germany) Cycle<br />
Sequencing Kits <strong>and</strong> analysed on an ABI Prism 3700 (Applied<br />
Biosystems, Foster City, CA) under conditions recommended by<br />
the manufacturer. Newly generated sequences were subjected<br />
to a Blast search of the NCBI databases, sequences with high<br />
<strong>similar</strong>ity were downloaded from GenBank <strong>and</strong> comparisons<br />
were made based on the alignment of the obtained sequences.<br />
Sequences from GenBank were also selected for <strong>similar</strong> taxa. <strong>The</strong><br />
LSU tree was rooted using sequences of Athelia epiphylla Pers.<br />
<strong>and</strong> Paullicorticium ansatum Liberta as outgroups. Phylogenetic<br />
analysis was performed with PAUP (Phylogenetic Analysis Using<br />
Parsimony) v. 4.0b10 (Swofford 2003), using the neighbour-joining<br />
algorithm with the uncorrected (“p”), the Kimura 2-parameter <strong>and</strong><br />
the HKY85 substitution models. Alignment gaps longer than 10<br />
bases were coded as single events for the phylogenetic analyses;<br />
the remaining gaps were treated as missing data. Any ties were<br />
broken r<strong>and</strong>omly when encountered. Phylogenetic relationships<br />
were also inferred with the parsimony algorithm using the heuristic<br />
search option with simple taxon additions <strong>and</strong> tree bisection <strong>and</strong><br />
reconstruction (TBR) as the branch-swapping algorithm; alignment<br />
gaps were treated as a fifth character state <strong>and</strong> all characters were<br />
unordered <strong>and</strong> of equal weight. Branches of zero length were<br />
collapsed <strong>and</strong> all multiple, equally parsimonious trees were saved.<br />
Only the first 5 000 equally most parsimonious trees were saved.<br />
Other measures calculated included tree length, consistency<br />
index, retention index <strong>and</strong> rescaled consistency index (TL, CI, RI<br />
<strong>and</strong> RC, respectively). <strong>The</strong> robustness of the obtained trees was<br />
evaluated by 1 000 bootstrap replications. Bayesian analysis was<br />
performed following the methods of Crous et al. (2006c). <strong>The</strong> best<br />
nucleotide substitution model was determined using MrModeltest<br />
v. 2.2 (Nyl<strong>and</strong>er 2004). MrBayes v. 3.1.2 (Ronquist & Huelsenbeck<br />
2003) was used to perform phylogenetic analyses, using a general<br />
time-reversible (GTR) substitution model with inverse gamma<br />
rates, dirichlet base frequencies <strong>and</strong> the temp value set to 0.5. New<br />
sequences were lodged with NCBI’s GenBank (Table 1) <strong>and</strong> the<br />
alignment <strong>and</strong> trees with TreeBASE (www.treebase.org).<br />
Morphology<br />
Cultural growth rates <strong>and</strong> morphology were recorded from colonies<br />
grown on MEA for 2 wk at 24 ºC in the dark, <strong>and</strong> colony colours<br />
were determined by reference to the colour charts of Rayner (1970).<br />
Microscopic observations were made from colonies cultivated on<br />
MEA <strong>and</strong> OA (oatmeal agar, Gams et al. 2007), using a slide culture<br />
technique. Slide cultures were set up in Petri dishes containing 2<br />
mL of sterile water, into which a U-shaped glass rod was placed,<br />
extending above the water surface. A block of freshly growing<br />
fungal colony, approx. 1 cm square was placed onto a sterile<br />
microscope slide, covered with a somewhat larger, sterile glass<br />
cover slip, <strong>and</strong> incubated in the moist chamber. Fungal sporulation<br />
was monitored over time, <strong>and</strong> when optimal, images were captured<br />
by means of a Nikon camera system (Digital Sight DS-5M, Nikon<br />
Corporation, Japan). Structures were mounted in lactic acid, <strong>and</strong><br />
30 measurements (× 1 000 magnification) determined wherever<br />
possible, with the extremes of spore measurements given in<br />
parentheses.<br />
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