Spontaneous circadian rhytms in a cold adapted native Aureobasidium pullulans

D.LORENA FRANCO , CAROLINA REZAVAL , ALFREDO CÁCERES , ALEJANDRO F. SCHINDER AND M. FERNANDA CERIANI; DIEGO LIBKIND; PAULO CANESA; NICOLAS BELLORA; SEBASTIAN RISAU; PABLO GLEISER; LUIS LARRONDO; LUCIANO MARPEGAN

Trento

Congreso; 27th International Conference on Yeast Genetics and Molecular Biology; 2015

Rhythmic environmentsshaped the evolution of circadian timing systems capable of synchronizingendogenous biological processes to day/night cycles. This entrainment iscritical for the health and survival of individual organisms and populations,and is based on transcriptional-translational feedback loops that generateclose to 24hr oscillations in gene expression and physiology, even in theabsence of external timing cues. Circadian systems are found from cyanobacteriato mammals, and though they involve different genes in diverse organisms, thebasic mechanisms of cellular circadian timekeeping are similar in all knowncircadian clocks.The circadian system infungi is well described, though mostly from mutant strains of N. crassa andin very specific growth conditions. It is not known if the molecularclock described for N. crassa is present in yeasts, and if so, howcircadian phenotypes in these organisms could be exploited biotechnologically.Working under thehypothesis that natural circadian traits are more likely to be retained byenvironmental strains rather than their lab counterparts, Aureobasidiumpullulans CRUB 1823, a psychrotolerant yeast with biotechnologicalpotential, was isolated from natural sources, screened for spontaneouscircadian phenotypes, and for expression of circadian clock genes (qPCR). Whengrown on solid media, colonies displayed daily formation of concentric ringswith morphology and frequency dependent on light exposure. Rings were presentin cultures grown in 12hr/12hr light/dark cycles and persisted in constantdarkness, indicating that ring formation is controlled by an endogenouscircadian clock and light. A gene expression analysis revealed that A.pullulans express the N. crassa clock-genes frq, wc-1, wc-2, andvvd suggesting a conserved circadian clock.Further work is beingdone to evaluate if the circadian clock in A. pullulans can modulate theexpression of biotechnologically relevant genes and products including pullulan(used for production of edible biofilms), Aureobasidin A (fungicidal) and hydrolyticenzymes. Such knowledge could be used to develop efficient and economicalstrategies to improve production by using appropriate lighting schedules ortiming of harvest. It will also broaden our knowledge about the general basisof fungal circadian clocks, in particular of cold adapted organisms, and theirimportance to fungal survival.