Production of calcium oxalate crystals by the basidiomycete Moniliophthora perniciosa, the causal agent of Witches Broom Disease of cacao.
Rio, M.C.S. do; Oliveira, B.V.; Thomazella, D.P de T.; Silva, J.A.F. da; Pereira, G.A.G. Current Microbiology. 56(4):363-370, Abril de 2008. doi:10.1007/s00284-007-9091-7(03/01/2008). 2008
Oxalic acid has been shown as a virulence factor
for some phytopathogenic fungi, removing calcium from
pectin and favoring plant cell wall degradation. Recently, it
was published that calcium oxalate accumulates in infected
cacao tissues during the progression of Witches’ Broom
disease (WBD). In the present work we report that the
hemibiotrophic basidiomycete Moniliophthora perniciosa,
the causal agent of WBD, produces calciumoxalate crystals.
These crystals were initially observed by polarized light
microscopy of hyphae growing on a glass slide, apparently
being secreted from the cells. The analysis was refined by
Scanning electron microscopy and the compositon of the
crystals was confirmed by energy-dispersive x-ray spectrometry.
The production of oxalate by M. perniciosa was
reinforced by the identification of a putative gene coding for
oxaloacetate acetylhydrolase, which catalyzes the hydrolysis
of oxaloacetate to oxalate and acetate. This gene was
shown to be expressed in the biotrophic-like mycelia, which
in planta occupy the intercellular middle-lamella space, a
region filled with pectin. Taken together, our results suggest
that oxalate production by M. perniciosa may play a role in
the WBD pathogenesis mechanism.