Light regulation of metabolic pathways in fungi

Light represents a major carrier of information in nature. The molecular machineries translating its electromagnetic energy (photons) into the chemical language of cells transmit vital signals for adjustment of virtually every living organism to its habitat. Fungi react to illumination in various ways, and we found that they initiate considerable adaptations in their metabolic pathways upon growth in light or after perception of a light pulse. Alterations in response to light have predominantly been observed in carotenoid metabolism, polysaccharide and carbohydrate metabolism, fatty acid metabolism, nucleotide and nucleoside metabolism, and in regulation of production of secondary metabolites. Transcription of genes is initiated within minutes, abundance and activity of metabolic enzymes are adjusted, and subsequently, levels of metabolites are altered to cope with the harmful effects of light or to prepare for reproduction, which is dependent on light in many cases. This review aims to give an overview on metabolic pathways impacted by light and to illustrate the physiological significance of light for fungi. We provide a basis for assessment whether a given metabolic pathway might be subject to regulation by light and how these properties can be exploited for improvement of biotechnological processes

Radiolaria and Phaeodaria

Polycystina (~400–800 living species and several thousand extinct forms) and Phaeodaria (~400–500 living species) are exclusively marine, open-ocean planktonic protists, most of which possess elaborate siliceous skeletons. The cytoplasm is divided into an internal part (endoplasm) separated from the external, more vacuolated one (ectoplasm) by a perforated membrane – the central capsule. The Polycystina protrude long and slender cytoplasmic projections (axopodia) supported internally by a rigid central rod (axoneme); while the Phaeodria have anetwork ofperipheral finely interconnectedpseudopodia.Afew Polycystina are colonial, but most, as well as all Phaeodaria, are solitary, around 40 μm to almost 2 mm in size. Most polycystine species peak in abundance between 0 and 100 m, whereasphaeodarianstendtolivedeeper,oftenbelow300m.Polycystineshavea rich fossil record dating from the Cambrian and are important for stratigraphic, paleoecologic, and evolutionary studies. The world-wide biogeography and diversity of radiolarians is chiefly governed by water temperature. Radiolarian prey includes bacteria, algae, protozoa, and microinvertebrates. Many surfacedwelling species of Polycystina possess symbiotic algae and photosynthetic cyanobacteria that provide nourishment to the host. Some colonial radiolaria reproduce by binary fission of the central capsules. Sexual reproduction of polycystines or Phaeodaria has not been confirmed, but the release of motile swarmers, likely gametes, has been widely documented. In species with a radial symmetry (Spumellaria) shell-growth is centrifugal, whereas in the Nassellaria the internal cephalic elements and the cephalis appear first. Individual longevity is estimated to range between 2 and 3 weeks and 1–2 months