Inhibition of Ecto-Phosphatase Activity in Conidia Reduces Adhesion and Virulence of Metarhizium anisopliae on the Host Insect Dysdercus peruvianus

Abstract

Metarhizium anisopliae is an entomopathogenic fungus with the ability to infect a broad range of arthropods, and have evolved distinct strategies for their attachment to hosts. Here, we describe the characterisation of ecto-phosphatase activity on the conidia surface of M. anisopliae and its relevance in the host interaction process. Ecto-phosphatase activity was linear for 60 min and during this time, was linear with the increase of cell density. The optimum pH was in the acidic range and some divalent metals, such as Cu(2+), Cd(2+) and Zn(2+), inhibited ecto-phosphatase activity. The activity was also reduced by phosphatase inhibitors. Importantly, the inhibition of phosphatase activity in conidia reduced the adhesion to Dysdercus peruvianus (Hemiptera: Pyrrhocoridae) integument and, consequently and indirectly, M. anisopliae infection. The results herein presented show, for the first time, the importance of ecto-phosphatase activity in M. anisopliae conidia and provide the first evidence of its direct involvement in adhesion and host infection.

Biochemical Properties and Possible Roles of Ectophosphatase Activities in Fungi

“…In fungi, ectophosphatases have been described in a large number of species, including Saccharomyces cerevisiae [25], Sporothrix schenckii [32], Paracocciodiodes brasiliensis [24], Candida parapsilosis [33,34], Kluyveromyces marxianus [35], Aspergillus fumigatus [36], Fosencaea pedrosoi [37,38], Cryptococcus neoformans [39], Pseudallescheria boydii [40], Candida albicans [41], Rhinocladiella aquaspersa [42] and Metarhizium anisopliae [43]. It is noteworthy that this review focuses on medically relevant fungal species.…”

“…The p -NPP hydrolysis generates inorganic phosphate (P i ) and p -nitrophenol ( p -NP), which turns yellow under alkaline conditions and can be quantified spectrophotometrically. This approach was performed with S. cerevisiae [25], C. parapsilosis [33,34], F. pedrosoi [37,38], C. neoformans [39], P. boydii [40], C. albicans [41], R. aquaspersa [42] and M. anisopliae [43]. …”

“…A secreted phosphatase has also been identified in S. cerevisiae in a study involving both cell-free preparations and intact cells [25]. Recently, it was observed that conidial forms of M. anisopliae express both ectophosphatase and secreted phosphatase activity [43]. This ectophosphatase activity has been fully characterized and comparison with a secreted phosphatase activity reported in the mycelial form of the same fungus indicates that they have different biochemical properties [43,44].…”

“…In general, fungal ectophosphatase activities are acid phosphatases that present high affinity for phosphotyrosine analog substrates such as p -NPP [25,32–39,42,43,48]. Hydrolysis of phosphorylated amino acids was examined in the mycelial and conidial forms of F. pedrosoi [37,38], C. parapsilosis [34] and P. boydii [40].…”

Biological insect control using Metarhizium anisopliae: morphological, molecular, and ecological aspects

“…The participation of an adhesin coded by the gene Mad1 in the adhesion of conidia to the cuticle of Manduca sexta Linnaeus larva was demonstrated using mutants in which this gene was deleted, with these mutants demonstrating signifi cant decreases in conidial germination, suppression of the formation of blastospores, and reduced virulence (WANG & St. LEGER, 2007a). COSENTINO-GOMES et al (2013) described that the inhibition of phosphatase activity in the conidia of M. anisopliae reduced adhesion to the integument of Dysdercus peruvianus (Hemiptera: Pyrrhocoridae) and (indirectly) its infection.…”