Research Article |
Corresponding author: Hiran A. Ariyawansa ( ariyawansa44@ntu.edu.tw ) Academic editor: Thorsten Lumbsch
© 2018 Hiran A. Ariyawansa, Alan J.L. Phillips, Wei-Yu Chuang, Ichen Tsai.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ariyawansa HA, Phillips AJL, Chuang W-Y, Tsai I (2018) Tzeananiaceae, a new pleosporalean family associated with Ophiocordyceps macroacicularis fruiting bodies in Taiwan. MycoKeys 37: 1-17. https://doi.org/10.3897/mycokeys.37.27265
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The order Pleosporales comprises a miscellaneous group of fungi and is considered to be the largest order of the class Dothideomycetes. The circumscription of Pleosporales has undergone numerous changes in recent years due to the addition of large numbers of families reported from various habitats and with a large amount of morphological variation. Many asexual genera have been reported in Pleosporales and can be either hyphomycetes or coelomycetes. Phoma-like taxa are common and have been shown to be polyphyletic within the order and allied with several sexual genera. During the exploration of biodiversity of pleosporalean fungi in Taiwan, a fungal strain was isolated from mycelium growing on the fruiting body of an Ophiocordyceps species. Fruiting structures that developed on PDA were morphologically similar to Phoma and its relatives in having pycnidial conidiomata with hyaline conidia. The fungus is characterised by holoblastic, cylindrical, aseptate conidiogenous cells and cylindrical, hyaline, aseptate, guttulated, thin-walled conidia. Phylogenetic analysis based on six genes, ITS, LSU, rpb2, SSU, tef1 and tub2, produced a phylogenetic tree with the newly generated sequences grouping in a distinct clade separate from all of the known families. Therefore, a new pleosporalean family Tzeananiaceae is established to accommodate the monotypic genus Tzeanania and the species T. taiwanensis in Pleosporales, Dothideomycetes. The Ophiocordyceps species was identified as O. macroacicularis and this is a new record in Taiwan.
Entomopathogenic fungi, Dothideomycetes , Multi-gene analysis, Phoma-like, Pleosporineae
We have been studying the families of Pleosporales considering both morphology and molecular phylogeny with the aim of providing a natural classification of this large order (
The Pleosporales is considered to be the largest and the most diverse order of the class Dothideomycetes, comprising over 4700 species classified in 53 families (
Pleosporales comprises the suborders Pleosporineae and Massarineae. (
Taiwan is an island located in the western Pacific Ocean and the importance of Taiwan’s rich diversity of fungal species has been often stated in Asian and global studies (
During the course of an exploration of ascomycetous fungi in Nantou County, Taiwan (24°06'20"N, 121°11'13"E) in July 2017, fungal mycelium was observed developing on a fruiting body of an unidentified Ophiocordyceps species. The mycelium was transferred to and spread on a Petri-dish containing 2% water agar (WA) and incubated at 25 °C. Single conidial isolates were established from sporulating conidiomata in Petri-dishes containing WA. Germinated conidia were transferred separately to plates of PDA (Ariyawansa et al. 2016 a, b).
Morphological descriptions were made from isolates cultured on 2% potato dextrose agar (PDA; Difco). Preparations for microscopy were mounted in distilled water, observed with an Olympus BX51 microscope with differential interference contrast (DIC) illumination and at least 30 measurements per structure were noted. Voucher specimens were deposited in the herbarium of Department of Plant Pathology and Microbiology, National Taiwan University (NTUH). Living cultures are stored at the Department of Plant Pathology and Microbiology, National Taiwan University Culture Collection (NTUCC). Taxonomic descriptions and nomenclature details were deposited in MycoBank.
Single conidial isolates were grown on PDA for 28 days at 25 °C in the dark. Genomic DNA was extracted from the mycelium using the Bioman Fungus Genomic DNA Extraction Kit (Bioman) following the manufacturer’s protocol (BIOMAN SCIENTIFIC CO., LTD). For Ophiocordyceps species, single spore isolation was not successful. Therefore DNA was extracted directly from the ascomata using a DNA extraction kit (E.Z.N.A. Forensic DNA kit, D3591-01, Omega Bio-Tek) following the protocol of
PCR amplification was conducted in a 50 μl reaction volume containing 5–10 ng DNA, 0.8 units Taq polymerase, 1X PCR buffer, 0.2 mM d’NTP, 0.3 μM of each primer with the addition of 1.5 mM MgCl2 (
Comparison of alignment properties of genes and nucleotide substitution models used in Pleosporales phylogenetic analysis.
LSU | SSU | rpb2 | tef1 | ITS | tub2 | |
---|---|---|---|---|---|---|
Alignment strategy (MAFFT v6) | G-INS-1 | G-INS-1 | G-INS-1 +manual | G-INS-1 +manual | G-INS-1 +manual | G-INS-1 +manual |
Nucleotide substitution models for Bayesian analysis (determined by MrModeltest) | GTR+I+G | HKY+I+G | GTR+I+G | GTR+I+G | GTR+I+G | GTR+I+G |
Multiple sequence alignments were produced with MAFFT v. 6.864b (http://mafft.cbrc.jp/alignment/server/index.html). The alignments were checked visually and adjusted manually where required. Two different datasets were prepared to evaluate two phylogenies; a Pleosporales tree and a phylogeny of the genus Ophiocordyceps. The first tree focused on phylogenetic placement of the new family Tzeananiaceae introduced in this study in the Pleosporales and the second to determine the placement of the Ophiocordyceps species (NTUH 17-004) within the genus Ophiocordyceps. All introns and exons were aligned individually. Regions comprising various leading or trailing gaps were excluded from the ITS, LSU, rpb2, SSU, tef1 and tub2 alignments prior to tree building. All sequences obtained from GenBank and used by
Maximum parsimony (MP) analyses were made using PAUP v. 4.0b10 (
Evolutionary models for each locus were determined individually using MrModeltest v. 2.3 (
A maximum likelihood analysis (ML) was executed at the CIPRES webportal (
Bayesian Markov Chain Monte Carlo (MCMC) analyses were conducted in MrBayes 3.1.2 (
Phylogenetic trees and data files were viewed in MEGA v. 5 (
Phylogenetic tree (RAxML) obtained from the DNA sequence data of ITS, LSU, rpb2, SSU, tef1 and tub2 sequences of 64 strains showing taxa in suborders Massarineae and Pleosporineae within Pleosporales. The new isolates are shown in bold, red. MP and ML bootstrap values (BS) ≥70% and Bayesian posterior probabilities (PP) ≥0.95 are presented at the nodes. Several branches were shortened to facilitate presentation of the tree and this is indicated by two diagonal lines with the number of times a branch was shortened. The scale bar shows the number of estimated mutations per site. The tree was rooted to Preussia terricola (DAOM 230091).
Phylogenetic tree (RAxML) obtained from the DNA sequence data of two loci (ITS and LSU) of Ophiocordyceps macroacicularis and allied taxa. The new strain is shown in bold. MP and ML bootstrap values ≥70% and Bayesian posterior probabilities ≥0.95 are presented at the nodes and the scale bar shows the number of estimated mutations per site. The tree was rooted to Ophiocordyceps sinensis (EFCC 7287).
Comparison of alignment properties of genes and nucleotide substitution models used in Ophiocordyceps and allied species phylogenetic analysis.
LSU | ITS | |
Alignment strategy (MAFFT v6) | G-INS-1 | G-INS-1 +manual |
Nucleotide substitution models for Bayesian analysis (determined by MrModeltest) | GTR+I | GTR+I+G |
The data for the trees conducted in the different analyses are shown below. In the multi-gene analyses, the topologies of the trees acquired for the individual loci were checked visually to confirm that the overall tree topology of the single datasets were comparable to each other and to that of the tree obtained from the combined dataset alignment. Phylogenetic trees obtained from the combined gene analyses are supplied below (Figs
The final alignment comprised 64 strains with 4558 characters (SSU 1019, LSU 877, ITS 450, rpb2 1013, tef1 902 and tub2 297). The maximum parsimony dataset consisted of 4558 characters of which 3226 were constant, 271 were variable and parsimony-uninformative and 1061 characters were parsimony-informative. Kishino-Hasegawa (KH) test showed length = 4234 steps, CI = 0.466, RI = 0.593, RC = 0.277 and HI = 0.534. The MCMC analysis of the six combined genes run for 66 × 104 generations resulted in 6600 trees. The first 1320 trees, representing the burn-in phase of the analyses, were discarded, while the remaining trees were used to calculate posterior probabilities in the majority rule consensus tree.
A best scoring RAxML tree is presented in Fig.
The phylogenetic tree separated two distinct clades corresponding to the suborders Massarineae (represented only by the family Didymosphaeriaceae) and Pleosporineae (represented by more than 19 families). The two newly isolated strains from this study (NTUCC 17-005 and NTUCC 17-006) formed a distinct clade basal to the familial clades of Shiraiaceae and Phaeosphaeriaceae with high BS and PP support in analyses of the single locus and concatenated datasets. Hence, the novel lineage is regarded here as the new family Tzeananiaceae.
The final Ophiocordyceps alignment comprised 12 strains. The dataset consisted of 1523 characters (LSU 899 and ITS 624). The Bayesian analysis resulted in 1 × 104 trees after 1 × 106 generations. The first 2,000 trees, showing the burn-in phase of the analyses, were discarded, while the remaining trees were used to calculate posterior probabilities in the majority rule consensus tree.
The best scoring RAxML tree is shown in Fig.
Ophiocordyceps macroacicularis (NTUH 17-004), considered in this study, grouped in a well-supported clade with isolates NBRC 100685, NBRC 105888 and NBRC 105889 of Ophiocordyceps macroacicularis that were used by
Sexual morph: undetermined. Asexual morph: Conidiomata pycnidial, solitary or aggregated, erumpent, globose, dark brown to black. Conidiomatal wall of textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells phialidic, hyaline, smooth-walled, ampulliform. Conidia hyaline, cylindrical, guttulate.
Named after the Taiwanese mycologist, Shean-Shong Tzean, in recognition of his extensive contributions towards the taxonomy of entomopathogenic fungi.
Tzeanania taiwanensis Ariyawansa, A.J.L. Phillips & Chuang.
Sexual morph: undermined. Asexual morph: Conidiomata pycnidial, partially or entirely immersed in the agar, solitary or aggregated, erumpent, globose. Conidiomatal wall of textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells phialidic, hyaline, smooth-walled, ampulliform. Conidia hyaline, smooth- and thin-walled, cylindrical, guttulate. Chlamydospores not observed in culture.
TAIWAN. Cueifong, Nantou County (24°06'20"N, 121°11'13"E), developing on a fruiting body of Ophiocordyceps macroacicularis, 9 July 2017, Wei-Yu Chuang, (holotype: permanently preserved in a metabolically inactive state, NTUH 17-005!; culture ex-holotype NTUCC 17-005!).
Phylogeny based on ITS, LSU, rpb2, SSU, tef1 and tub2 revealed that the strains NTUCC 17-005 and NTUCC 17-006 considered in the present study formed a separate lineage sister to the familial clades of Shiraiaceae and Phaeosphaeriaceae in suborder Pleosporineae. Therefore, a new genus Tzeanania, a new species T. taiwanensis and a new family Tzeananiaceae in suborder Pleosporineae, Pleosporales are proposed here for the pycnidial coelomycete growing on the surface of the fruiting body of Ophiocordyceps macroacicularis.
The epithet refers to Taiwan, where this species was collected
Developing on the fruiting body of Ophiocordyceps macroacicularis.
Sexual morph not observed. Asexual morph: Conidiomata pycnidial, semi- or entirely immersed in the agar, solitary or aggregated, erumpent, globose, dark brown to black. Conidiomatal wall of textura angularis, 3–5 layered, composed of brown to dark brown, flattened polygonal cells. Conidiophores reduced to conidiogenous cells. Conidiogenous cells phialidic, hyaline, smooth-walled, ampulliform to globose, 3–5 × 0.5–2 μm, x¯ ± SD = 4 ± 0.7 × 1.5 ± 0.3 μm. Conidia hyaline, smooth-walled, thin-walled, cylindrical, guttulate, 4–6 × 1–2 μm, x¯ ± SD = 5.3 ± 0.27 × 1.5 ± 0.08 μm. Chlamydospores not observed in culture.
Colonies concentric circular pattern with radial furrows, entire, whitish, grey to olivaceous, with black conidiomata clustered in circular distribution; reverse concentric circular pattern with radial furrows, beige around centre and olivaceous at edge.
Taiwan
TAIWAN. Department of Plant Pathology and Microbiology, National Taiwan University, growing on a pine needles, 10 October 2017, Wei-Yu Chuang, (paratype: NTUH 17-006!, culture ex-paratype NTUCC 17-006!).
Tzeanania taiwanensis differs from the familial type of Phaeosphaeriaceae, Phaeosphaeria oryzae in having erumpent, globose conidiomata, conidiomatal wall 3–5 layered, with cylindrical, aseptate, hyaline conidiogenous cells and cylindrical, hyaline, aseptate, guttulated, thin-walled conidia. Phaeosphaeria oryzae has immersed, uni- to multi-loculate, globose to subglobose conidiomata, conidiomatal walls comprising brown pseudoparenchymatous cells, with flattened ampulliform to doliiform, hyaline to pale brown conidiogenous cells and oblong to cylindrical, pale brown to brown, septate, smooth-walled guttulate conidia (
Morphologically, Tzeanania taiwanensis differs from the familial type of Shiraiaceae, Shiraia bambusicola in having aseptate conidiogenous cells and cylindrical, hyaline, aseptate, guttulated, thin-walled conidia. Shiraia bambusicola has septate conidiogenous cells producing fusiform, muriform, hyaline to light brown, thick-walled conidia with irregularly arranged transverse and longitudinal septa (
In this study, a new family Tzeananiaceae is formally proposed in Pleosporineae, Pleosporales. This fungus was found on the surface of the fruiting bodies of Ophiocordycepsmacroacicularis. Phylogenetic analyses, based on DNA sequence data of ITS, LSU, rpb2, SSU, tef1 and tub2, revealed it to form a separate lineage from all other families of Pleosporales. Ophiocordyceps macroacicularis is reported for the first time from Taiwan. Moreover, our study expands the base of information regarding the diversity of pleosporalean fungi associated with entomogenous taxa in Taiwan.
Molecular data play a crucial part in present-day fungal systematics, but have some limitations (
The family Shiraiaceae was introduced by
Phaeosphaeriaceae is one of the largest families in suborder Pleosporineae and includes economically important phytopathogens (
Phylogenetically, Tzeanania has close affinity with Shiraiaceae and Phaeosphaeriaceae. To clarify the phylogeny of Shiraia-like fungal isolates,
Ophiocordyceps macroacicularis S. Ban et al. was introduced by
This study was funded by the Ministry of Science and Technology, Taiwan (MOST project ID: 106-2621-B-002-005-MY2). Alan J.L. Phillips acknowledges the support from Biosystems and Integrative Sciences Institute (BioISI, FCT/UID/ Multi/04046/2013). We appreciate the support given by Professors CP Lin, WC Shen, TL Shen, RF Liou, Associate Professor CL Chung and Chia-Ming Hu. H. A. Ariyawansa is grateful to A.D Ariyawansa, D.M.K Ariyawansa, Ruwini Ariyawansa and Amila Gunasekara for their valuable suggestions.