EXPRESSION ANALYSIS OF GENES INVOLVED IN C/N BALANCE IN RESPONSE TO STRESS IN MICROCYSTIS STRAINS

MARTIN, MARÍA VICTORIA; CAINZOS, MAXIMILIANO; KOLMAN, MARÍA DE LOS ÁNGELES; SALERNO, GRACIELA

Mar del Plata

Congreso; LI Reunión Anual de la Sociedad Argentina de Investigació en Bioquímica y Biología Molecular (SAIB).; 2015

Cyanobacteria are oxygenic photosynthetic organisms foundin different habitats that play a key role in the biogeochemical C/N cycle. Theirability to assimilate CO2 from the environment comes from the CarbonConcentrating Mechanisms (CCM), which comprises inorganic carbon (Ci, as CO2and HCO3-), transportersfor Ci uptake and protein microbodies (carboxysomes). CO2concentration and fixation by Rubisco take place in the CCM.Microcystis strains produce blooms and are also able tosynthesize microcystins, powerful hepatotoxins. Recently, it was shown thatmicrocystins bind to some proteins, such as those belonging to thecarboxysomes, giving them stability during periods of oxidative stress, afairly common condition in a bloom. Also, it was reported that genes encodingproteins involved in microcystin synthesis are up-regulated under stressconditions. Studies comparing Microcystis strains showed that nine proteinsinvolved in C and N metabolism and in maintaining the redox balance exhibitdifferential expression regarding microcystin synthesis. In the present work, we analyzed the expression ofgenes involved in C and N assimilation, microcystin synthesis, and redoxbalance in a model and in a native toxic Microcystis strains, under different C/N ratio and stressconditions. In the model strain, gene expression was up-regulated at higher C/Nratios. Interestingly, in the nativestrain, expression of those genes was constitutivelyhigh even under control conditions. Our data support that microcystinproduction is related to stress and may be involved in cyanobacteria survival.Supported by CONICET, UNMdP and FIBA.