HOW DO THEY COPE WITH DESERT CONDITIONS: PHYSIOLOGICAL, GENOMIC AND TRANSCRIPT PROFILING UNCOVERED A NOVEL RELEVANT RNA AND PROTEIN STABILIZING MECHANISMS

Microorganisms inhabiting biological desert soil crusts (BSC) are likely equipped to cope with one of the harshest environmental conditions on earth including daily hydration/dehydration cycles, high irradiance and extreme temperatures. Of particular interest are the unicellular photosynthetic species the primary producers bearing genes that enable them not only to survive, but also maintain active and efficient photosynthesis in such extreme conditions. From both the basic science and biotechnological/agricultural perspectives, identification and characterization of these genes may contribute to our understanding of stress biology and enhance the tolerance of sensitive organisms. Our case of study is Leptolyngbya ohadii, a filamentous cyanobacterium able to revive even after severe dehydration. Using full genome sequencing, assembly and annotation, transcriptome analyses of isolated cultures under optimal and stressful conditions, comparative genomics and correlating them with physiological data we found groups of both known and novel genes, likely to play significant role in this habitat. Comparative genomics identified a set of 36 genes present in desiccation-tolerant but not in sensitive cyanobacteria. Analysis of gene expression profiles during desiccation/rehydration cycles revealed a strong regulatory network of the acclimation process controlled by both light and temperature. Profiling of specific protein levels revealed redox dependent interchanges between complexes and monomeric forms. The data uncovered a novel RNA and protein stabilizing mechanisms that plays a significant role in the ability of these organisms to survive in the harsh desert ecosystem.