Thermal adaptation strategies of the extremophile bacterium Thermus filiformis based on multi-omics analysis.

Thermus filiformis is an aerobic thermophilic bacterium isolated from a hot spring in New Zealand. The experimental study of the mechanisms of thermal adaptation is important to unveil response strategies of the microorganism to stress. In this study, the main pathways involved on T. filiformis thermoadaptation, as well as, thermozymes with potential biotechnological applications were revealed based on omics approaches. The strategy adopted in this study disclosed that pathways related to the carbohydrate metabolism were affected in response to thermoadaptation. High temperatures triggered oxidative stress, leading to repression of genes involved in glycolysis and the tricarboxylic acid cycle. During heat stress, the glucose metabolism occurred predominantly via the pentose phosphate pathway instead of the glycolysis pathway. Other processes, such as protein degradation, stringent response, and duplication of aminoacyl-tRNA synthetases, were also related to T. filiformis thermoadaptation. The heat-shock response influenced the carotenoid profile of T. filiformis, favoring the synthesis of thermozeaxanthins and thermobiszeaxanthins, which are related to membrane stabilization at high temperatures. Furthermore, antioxidant enzymes correlated with free radical scavenging, including superoxide dismutase, catalase and peroxidase, and metabolites, such as oxaloacetate and α-ketoglutarate, were accumulated at 77 °C.

Transcription factors regulating leaf senescence in Arabidopsis thaliana.

Senescence is a highly regulated process, eventually leading to cell and tissue disintegration: a physiological process associated with nutrient (e.g. nitrogen) redistribution from leaves to reproductive organs. Senescence is not observed in young leaves, indicating that repressors efficiently act to suppress cell degradation during early leaf development and/or that senescence activators are switched on when a leaf ages. Thus, massive regulatory network re-wiring likely constitutes an important component of the pre-senescence process. Transcription factors (TFs) have been shown to be central elements of such regulatory networks. Here, we used quantitative real-time polymerase chain reaction (qRT-PCR) analysis to study the expression of 1880 TF genes during pre-senescence and early-senescence stages of leaf development, using Arabidopsis thaliana as a model. We show that the expression of 185 TF genes changes when leaves develop from half to fully expanded leaves and finally enter partial senescence. Our analysis identified 41 TF genes that were gradually up-regulated as leaves progressed through these developmental stages. We also identified 144 TF genes that were down-regulated during senescence. A considerable number of the senescence-regulated TF genes were found to respond to abiotic stress, and salt stress appeared to be the major factor controlling their expression. Our data indicate a peculiar fine-tuning of developmental shifts during late-leaf development that is controlled by TFs.