12 Tremellomycetes and Related Groups
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12 Tremellomycetes and Related Groups 1 1 2 1 MICHAEL WEIß ,ROBERT BAUER ,JOSE´ PAULO SAMPAIO ,FRANZ OBERWINKLER CONTENTS I. Introduction I. Introduction ................................ 00 A. Historical Concepts. ................. 00 Tremellomycetes is a fungal group full of con- B. Modern View . ........................... 00 II. Morphology and Anatomy ................. 00 trasts. It includes jelly fungi with conspicuous A. Basidiocarps . ........................... 00 macroscopic basidiomes, such as some species B. Micromorphology . ................. 00 of Tremella, as well as macroscopically invisible C. Ultrastructure. ........................... 00 inhabitants of other fungal fruiting bodies and III. Life Cycles................................... 00 a plethora of species known so far only as A. Dimorphism . ........................... 00 B. Deviance from Dimorphism . ....... 00 asexual yeasts. Tremellomycetes may be benefi- IV. Ecology ...................................... 00 cial to humans, as exemplified by the produc- A. Mycoparasitism. ................. 00 tion of edible Tremella fruiting bodies whose B. Tremellomycetous Yeasts . ....... 00 production increased in China alone from 100 C. Animal and Human Pathogens . ....... 00 MT in 1998 to more than 250,000 MT in 2007 V. Biotechnological Applications ............. 00 VI. Phylogenetic Relationships ................ 00 (Chang and Wasser 2012), or extremely harm- VII. Taxonomy................................... 00 ful, such as the systemic human pathogen Cryp- A. Taxonomy in Flow . ................. 00 tococcus neoformans. The systematics and B. Taxonomic Synopsis. ................. 00 taxonomy of many species now contained in C. Key Groups . ........................... 00 Tremellomycetes have significantly changed 1. Cystofilobasidiales . .............. 00 2. Filobasidiales . .............. 00 during the past three decades and are about to 3. Holtermanniales. .............. 00 change again as a result of changes in the taxo- 4. Trichosporonales. .............. 00 nomic treatment of anamorph forms in the 5. Tremellales . .............. 00 International Code of Nomenclature for algae, D. Possibly Related Taxa Incertae Sedis ... 00 fungi, and plants (McNeill et al. 2012). An 1. Bartheletia............................. 00 2. Wallemia . ................... 00 integrated systematic view of the Tremellomy- VIII. Conclusions ................................. 00 cetes has been hampered by the fact that the References. ............................. 00 anamorphic taxa, i.e., yeasts, and the basidiome-forming dimorphic taxa have tradi- tionally been studied by different scientific communities. Recently, the group has been dis- cussed in more integrative treatments (e.g., Boekhout et al. 2011; Millanes et al. 2011; Sam- Dedicated to the memory of Robert Joseph Bandoni paio 2004). (1926–2009) Since the last edition of The Mycota,key 1Fachbereich Biologie, Eberhard-Karls-Universita¨tTu¨bingen, Auf der Morgenstelle 1, 72076 Tu¨bingen, Germany; e-mail: systematic concepts in the Basidiomycota have [email protected];; changed conspicuously. While the tremello- 2Centro de Recursos Microbiolo´gicos, Departamento de Cieˆn- mycetous groups were then treated in a sepa- cias da Vida, Universidade Nova de Lisboa, 2829-516 Caparica, rate Heterobasidiomycetes chapter (Wells and Portugal Systematics and Evolution, 2nd Edition The Mycota VII Part A D.J. McLaughlin and J.W. Spatafora (Eds.) © Springer-Verlag Berlin Heidelberg 2014 M. Weiß et al. Bandoni 2001), Heterobasidiomycetes is no B. Modern View longer considered a monophyletic group (Weiß et al. 2004); for the present edition its This concept was challenged by Bandoni members are discussed in this chapter, in (1984), who redefined Tremellales and Auricu- Agaricomycetes (Tulasnella, Ceratobasidium lariales based on ultrastructural characters, the and relatives, Auriculariales, Sebacinales; see nature of the haploid states, and trophic strate- Hibbettetal.2014), and in Dacrymycetes (see gies, rather than on basidial morphology. This Oberwinkler 2014). alternative concept has been largely confirmed In this overview we provide an introduction by molecular data (e.g., Swann and Taylor 1995; to the taxonomy, morphology, ecology, and Weiß and Oberwinkler 2001) and is currently phylogenetic relationships of the Tremellomy- widely accepted (Hibbett et al. 2007). cetes, including a phylogenetic tree that covers Particular taxonomic problems in the Tre- the vast majority of species of this group for mellomycetes to be solved in the future include which molecular data [nuclear rDNA coding for the obvious nonmonophyly of established mor- the D1/D2 regions of the large ribosomal sub- phogenera, such as Tremella, and the question unit (LSU)] are available, using type or ex-type of how to best treat originally anamorphic sequences wherever possible. It illustrates both genera, such as Bullera and Cryptococcus,ina the phylogenetic resolution presently available modern nomenclature that no longer gives pri- in the Tremellomycetes and the degree to which ority to generic names based on teleomorphs current taxonomy matches the phylogenetic (Hawksworth 2011; McNeill et al. 2012). Since it relationships in this group. Considering the is too early to solve these questions in this text, impressive progress in genome sequencing here we still adopt some widely used names that and phylogenomics we anticipate that at least are likely to change in the near future. the higher-level relationships will be much bet- ter resolved in the near future. II. Morphology and Anatomy A. Historical Concepts A. Basidiocarps The genus Tremella was validly described by Basidiocarps (Fig. 12.1) are known from species Persoon (1794). Some years later (Fries 1821) of Tremellales, Holtermanniales, and Filobasi- thegenuswasthebasisforthefamilyTremel- diales (Syzygospora). In species of Tremellales, laceae (as Tremellini, including also Dacry- basidiocarps are mostly of a gelatinous consis- myces), and for the order Tremellales (as tency. Many species can undergo prolonged Tremellinae)—one of the six orders that Fries phases of exsiccation, reviving when rehy- described in his Hymenomycetes—which drated, with renewed growth and production roughly corresponds to what today are called of conidia or basidiospores (Wells and Bandoni jelly fungi. Since the acceptance of basidial 2001). They are thus well adapted to habitats on morphology as a key character in the system- dead wood, on which the more exposed species, atics of the basidiomycetes (Brefeld 1888; for example, Tremella, are often found. Basi- Patouillard 1887;Tulasne1853), Tremella- diocarp forms vary from pustulate, for exam- ceae/Tremellales have often been used as the ple, Tremella spp., Tetragoniomyces,or taxon containing all hymenomycetes with Sirobasidium,tocushion-shaped, lobose-cere- longitudinally septate basidia—as opposed briform, for example, Tremella mesenterica to the Auriculariaceae/Auriculariales, which (Fig. 12.1a, b), to foliose, for example, Tremella according to these concepts included taxa foliacea (Fig. 12.1g) and Tremella fuciformis with transversely septate basidia [see Bandoni (Fig. 12.1h). Often they originate from a host (1984) for a systematic treatment of the fungus that they obviously parasitize (see taxonomic history]. below). Mature basidiocarps may even show a Tremellomycetes and Related Groups Fig. 12.1 (a–e) Tremella mesenterica.(a) Young basi- fuciformis, bar¼3 cm. (i) Tremella aurantia, bar¼ diocarps on Peniophora laeta growing on Carpinus 3 cm. (j) Sirobasidium magnum, bar 3 cm. (k–m) Syzy- betulus, bar¼2 mm. (b) Mature basidiocarp, bar¼ gospora pallida.(k) Pustular basidiocarps emerging 5 mm. (c) Part of hymenium with basidia, bar¼ from host Phanerochaete cremea, bar¼2 mm. (l) Basid- 10 mm. (d) Yeast budding, bar¼10 mm. (e) Basidio- ium and conidiophores, bar¼10 mm. (m) Budding spore with secondary spore, bar¼5 mm. (f) Tremella yeasts, bar¼10 mm. (n, o) Tetragoniomyces uliginosus. encephala showing whitish core with hyphal mixture of (n) Basidiocarps in culture, bar¼1 mm. (o) Germinat- host Stereum sanguinolentum and mycoparasite, bar¼ ing basidium, bar¼10 mm 1 cm. (g) Tremella foliacea, bar¼2 cm. (h) Tremella M. Weiß et al. central core composed of hyphae of host and order, with transverse or oblique basidial mycoparasite, as in Tremella encephala septa,asinAuriculibuller, Bulleromyces, and (Fig. 12.1f). Basidiocarps in the Holterman- Papiliotrema (Fig. 12.2b). Development of the niales are tough-gelatinous, with a clavarioid basidial compartments is often strongly desyn- appearance. chronized (Wells and Bandoni 2001), and basi- Numerous teleomorphic species in the Tre- dial compartments may detach in some species, mellomycetes apparently lack basidiocarps. for example in Sirobasidium (Fig. 12.2h), before Such species grow intrahymenially in their fun- giving rise to a ballistospore (Bandoni 1984). gal hosts, either without causing any macro- Basidial septation may also be lacking, resulting scopic symptoms, such as Tremella giraffa, in holobasidia,asinCarcinomyces (Fig. 12.3d) Tremella obscura, and Tremella penetrans,or and Filobasidiella (Fig. 12.3a) (Tremellales); inducing galls on their hosts, for example, Filobasidium (Fig. 12.3b) and Syzygospora lichenicolous species of Tremella or Biatoropsis (Fig. 12.3e, f) (Filobasidiales); Cystofilobasi- usnearum. Sexual stages in some species of dium (Fig. 12.3c); and Xanthophyllomyces Tremellales, for example, Bulleribasidium (Cystofilobasidiales).