Only 14 of these were included in our initial set of Veliparib mouse U. maydis proteins used in the search for pHGRs,

since the rest did not show any signal peptide in the prediction carried out with SignalP. Interestingly, 13 of these 14 proteins were also predicted to be highly O-glycosylated in this study, in a region overlapping with the putative site serving as PMT4 substrate in all but in one case in which the pHGR and the PMT4 glycosylation site were adjacent. Bearing in mind that both the results reported in this study and those of Fernández-Álvarez et al.[6] are plain in silico predictions, the fact that they coincide to a great extent encourages using these predictions in the experimental search for highly O-glycosylated regions in proteins. We have found experimentally

some of the putatively hyper-O-glycosylated B. cinerea proteins in the early secretome. 26 of the 105 proteins identified in the early secretome Ro 61-8048 molecular weight [23] are predicted to have at least one pHGR (not shown). This group contains proteins with a diverse set of functions, but is enriched in proteins that seem to be involved in the metabolism of the cell wall or extracellular matrix, such as ß-1,3-glucanosyltransferase or ß-1,3-endoglucanase. The rest are lytic enzymes for various soluble substrates or proteins with unknown function. Intriguingly, with the only CX-5461 nmr exception of one endopolygalacturonase, no plant cell wall degrading enzymes were found in the set. This leads to the speculation of a possible role for HGRs in maintaining proteins in the extracellular matrix. Proteins involved in

turning soluble polymers into monomers, such as proteases or ribonucleases, could carry a better function if retained in the vicinity of the fungal cell, and bearing an hyper-O-glycosylated region could provide that property by integrating the proteins in the very prominent glucan sheath of B. cinerea [24, 25]. Another possible role for pHGRs could be to confer a specific topological configuration to the proteins. Such seems to be the case, for example, of the cell-surface GPI-anchored adhesin Epa1p from Candida glabrata PRKD3 [26], which bears a Ser/Thr-rich region proposed to be kept in an extended rode-like conformation by O-glycosylation [26]. This Ser/Thr region serves to protrude the proteins’ main body away from the GPI-anchored C-terminus on the cell membrane. Given the prevalence of pHGRs among fungal secretory proteins and the variety of properties they may confer to the proteins displaying them, it is not surprising that mutants affected in O-glycosylation show pleiotropic phenotypes [2], including reduced viability and virulence [5, 6]. O-glycosylation may be, therefore, worth exploring as a new target in the fight against fungal pathogens.