Gamarada debralockiae gen. nov. sp. nov.—the genome of the most widespread Australian ericoid mycorrhizal fungus

Abstract

This study describes a novel ericoid mycorrhizal fungus (ErMF), Gamarada debralockiae Midgley and Tran-Dinh gen. nov. sp. nov. Additionally, catabolism was explored from a genomic perspective. The nuclear and mitochondrial genomes of G. debralockiae were sequenced. Morphological characteristics were assessed on various media. Catabolic genes of G. debralockiae were explored using SignalP and dbCAN. Phylogenetic comparisons were undertaken using Phylogeny.fr. The 58.5-Mbp draft genome of G. debralockiae contained 17,075 putative genes. The complete mitochondrial genome was 28,168 bp in length. In culture, G. debralockiae produces slow-growing non-sporulating colonies. Gamarada debralockiae has many putative secreted catabolic enzymes. Phylogeny indicated G. debralockiae was distinct from known ascomycetous ErMF: Pezoloma ericae, Meliniomyces spp., Oidiodendron spp., and Cairneyella variabilis. It is closely related to many undescribed plant root-associated fungi and its nearest described relative is Hyphodiscus brevicollaris. Gamarada debralockiae has been recovered from virtually all Australian ericoid mycorrhizal studies and biogeographic data suggests the taxon is widespread in Australia. Gamarada debralockiae has similar catabolic potential to C. variabilis and co-occurs with C. variabilis at Australian sites. Plants that host multiple ErMF may benefit from subtle differences in catabolism that improve access to nitrogen and phosphorus from within recalcitrant organic matter.

Ericoid mycorrhizal symbiosis: theoretical background and methods for its comprehensive investigation

“…If resources are limited, several isolates per each conservatively established morphotype must be identified to confirm ingroup conspecificity. Many ericoid root mycobionts are unnamed and deserve taxonomic treatment, especially when represented by multiple isolates from different geographical and/or host contexts (for interesting thoughts on what makes a species worth naming, see Seifert 2017 , for an illustrative example of an ericoid mycobiont that had deserved to be named, see Midgley et al 2018 ). However, describing a new fungal species is a non-trivial process that comprises detailed morphological characterization and photodocumentation, deposition of the holotype (a metabolically inactive (e.g., dried) culture) as well as culture ex-types and annotated sequences in reliable and publicly accessible repositories, ideally multi gene phylogenetic analyses, registration in MycoBank, etc.…”

“…Koch's postulatesfor a detailed background, explanation, and current views on the postulates see https ://en.wikip edia.org/ wiki/Koch%27s_postu lates (Kolařík and Vohník 2018). That said, most of our knowledge on the ErMF diversity comes from the temperate and boreal ecosystems of the Northern Hemisphere and the real number of true ErMF is undoubtedly higher-for example, two new ascomycetous genera most probably representing ErMF (i.e., Cairneyella (Midgley et al 2016) and Gamarada (Midgley et al 2018)) have been recently described from Australian Styphelioideae. Research on the diversity and identity of mycobionts associated with ericoid roots especially outside the already explored areas (see Fig.…”

Continental‐scale metagenomics, BLAST searches, and herbarium specimens: The Australian Microbiome Initiative and the National Herbarium of Victoria

“…Although the study of fungal diversity has been biased toward Northern Hemisphere temperate ecosystems, there have been major efforts to reconcile the gap in knowledge regarding tropical and Southern Hemisphere fungi, with major foci of activity in the eastern paleotropics (Luo et al, 2016; Vadthanarat et al, 2018, 2019; Sukarno et al, 2019), Central and South America (Kuhar et al, 2017; Accioly et al, 2018; Kaishian and Weir, 2018; Ovrebo et al, 2019), Africa (Castellano et al, 2016; Buyck et al, 2018, 2019; Jami et al, 2018), and Australia (Midgley et al, 2018; Davoodian et al, 2019; Ji et al, 2019; Khmelnitsky et al, 2019).…”

“…, Africa (Castellano et al, 2016;Buyck et al, 2018Buyck et al, , 2019Jami et al, 2018), and Australia (Midgley et al, 2018;Davoodian et al, 2019;Ji et al, 2019;Khmelnitsky et al, 2019).…”

Fungi in hair roots of Vaccinium spp. (Ericaceae) growing on decomposing wood: colonization patterns, identity and in vitro symbiotic potential

“…In some ecosystems, ericaceous hair roots lack or are not dominated by the archetypal ErMF H. hepaticicola and O. maius and their place is taken by other mycobionts whose functioning is not fully understood (see (Bruzone et al 2015) and references therein). These often represent novel fungal lineages that occur in less explored locations (e.g., (Midgley et al 2016(Midgley et al , 2018Leopold et al 2021;Vohník et al 2022) and/or are di cult to grow in pure culture, e.g., members of Chaetothyriales (Allen et al 2003;Lukešová et al 2015;Toju et al 2016;Baba and Hirose 2021), Sebacinales (Allen et al 2003;Selosse et al 2007;Vohník et al 2016;Gri n and Kernaghan 2022) and Kurtia argillacea in Hymenochaetales (Kolařík and Vohník 2018). It has been suggested that some of them may confer adaptations distinct from those provisioned by the so far investigated ascomycetous ErMF, e.g., the ability to degrade recalcitrant aromatic substrates like lignin (Vohník et al 2012a), the second most abundant biopolymer on Earth (Baucher et al 1998).…”