Xylona heveae TC161 v1.0
Xylona heveae
Photo credit: Romina Gazis at Clark U.
Xylona heveae belongs to the recently described class Xylonomycetes (Ascomycota). This novel clade was described based on strains isolated mainly as sapwood endophytes of Hevea brasiliensis (rubber tree). Six loci were used to place this new lineage within the Leotiomyceta; however, its evolutionary relationships with the other classes still remain unresolved. We only know the morphology of its anamorphic state (A). Conidiomata are pycnidial, astromatic and composed of thin-walled cells forming tissue textura angularis. Conidial masses (B) are liberated through the apical rupture of the pycnidia (ostiole absent). Conidiophores are absent. Conidiogenous cells are enteroblastic, phialidic, discrete, hyaline and presented one collarette (C). Conidia are apically rounded with two lateral obtuse projections appearing heart-shaped (narrower and truncated at base), hyaline when young, turning dark brick when mature, aseptate, thick-walled, smooth and guttulated (D). After ca. 3 weeks, both types of agar acquired a vinaceous diffusing pigment, especially at the margins of the growing colony.

We believe that Xylona may represent a true endophytic lineage since no close relatives have been found as saprotrophs or plant pathogens, not even from environmental surveys. In marked contrast to many foliar endophytes, the strains we isolated failed to degrade cellulose and lignin in vitro, suggesting that this species might use different pathways to obtain nutrients from their hosts.

Xylona’s predicted unique genomic content and expression data could shed light into our understanding of the mechanisms behind endophytism. In addition, Xylona as the only representative of a highly distinct group of Ascomycota, might have novel enzymes and secondary metabolites of interest in bioprospection.

For more information

Gazis, R., J. Miadlikowska, F. Lutzoni, A. E. Arnold, and P. Chaverri. Cul- ture-based study of endophytes associated with rubber trees in Peru reveals a new class of Pezizomycotina: Xylonomycetes. Molecular Phylogenetics and Evolution (2012) 65: 294-304.

Genome Reference(s)