Potential Role of RTA3 and GNP3 Transport Genes in the Quorum Sensing Response of Candida Albicans

Quorum sensing (QS) is a mechanism of communication between cells to coordinate biological activities. In the opportunistic fungal pathogen Candida albicans, QS is important for regulating the organism’s ability to change morphology from a yeast form to a hyphal form. Previously, our laboratory identified several genes involved in polymicrobial communication between C. albicans and three bacterial species. We hypothesize that interspecies communication and QS utilize the same genetic pathways to control C. albicans morphological behavior. In this study, two transport genes, RTA3 and GNP3, and their involvement in QS were examined. To test whether these two genes participate in QS, a filamentation assay was performed using C. albicans wild type strain SC3514, along with CHK21, and the haploinsufficient strains hRTA3 and hGNP3. The cells were incubated under filamentation conditions in the presence or absence of tran,trans-farnesol, cyclic di-GMP, or pyocyanin. When exposed to farnesol, the hGNP3 mutant behaved more like the non-responder (CHK21), while hRTA3 showed a filamentation rate similar to that of the wild type (SC5314). When exposed to cyclic di-GMP, all four samples showed a mild inhibition of filamentation. Pyocyanin did not impact filamentation. In addition to filamentation, the mutants were evaluated for their ability to form biofilms. The impact of farnesol on biofilm formation for both haploinsufficient mutants fell between the ranges for the positive and negative controls. Biofilm assays utilizing cyclic di-GMP showed an increase in biofilm formation for all four samples, indicating an increase in overall biofilm mass despite the decreased filamentation previously shown