Differential roles of protein kinase A regulatory subunit isoforms in Mucor circinelloide

JOSEFINA OCAMPO; SILVIA MORENO; VICTORIANO GARRÉ MULA; SILVIA ROSSI

Potreo de Funes

Congreso; Annual Meeting SAIB; 2011

SAIB

PKA is a tetramer composed of two Regulatory (R) and two Catalytic subunits (C). We demonstrated the existence of 4 genes for R and 10 genes for C in M. circinelloides. In a previous work we disrupted the gene pkaR1 (R1 null) and described its role in growth and morphology. R1null showed a reduction in radial growth, alterations in germination rate, cell volume, germ tube length, and asexual sporulation. In the present work, we disrupted the genes pkaR2, pkaR3, and pkaR4 with the aim of analyzing if each PKAR isoform has a different role in the differentiation process. The germ tube emission in pkaR2 mutant is earlier than in wild-type strain (wt). PKAR4 appears to be essential for the fungus survival. The homokaryotic pkaR4 mutant strain was not stable; with the successive cultures it became heterokaryotic. pkaR4 mutant strain had an impediment to emit the germ tube in aerobic conditions and after the transition from anaerobic to aerobic conditions; it also has an increased cel volume. pkaR3 null shows slight differences from wt in the growth conditions analyzed. The expression of the pkaR genes was assessed in pkaR1, pkaR2 and pkaR3 nullby semiquantitative RT-PCR. Different mRNA expression was detected in the knockout strains for each pkaR gene. The results indicate that each PKAR isoform has a different role in M. circinelloides physiology, thus contributing to the specificity of cAMP-PKA pathway.