A variety of living organisms including bacteria, fungi, animals, and plants use blue light (BL) to adapt to changing ambient light. Photosynthetic forms (plants and algae) require energy of light for photosynthesis, movements, development, and regulation of activity. Several complex light-sensitive systems evolved in eukaryotic cells to use the information of light efficiently with photoreceptors selectively absorbing various segments of the solar spectrum, being the first components in the light signal transduction chain. They are most diverse in algae. Photosynthetic stramenopiles, which received chloroplasts from red algae during secondary symbiosis, play an important role in ecosystems and aquaculture, being primary producers. These taxa acquired the ability to use BL for regulation of such processes as phototropism, chloroplast photo-relocation movement, and photomorphogenesis. A new type of BL receptor - aureochrome (AUREO) - was identified in Vaucheria frigida in 2007. AUREO consists of two domains: bZIP (basic-region leucine zipper) domain and LOV (light-oxygen-voltage-sensing) domain, and thus this photoreceptor is a BL-sensitive transcription factor. This review presents current data on the structure, mechanisms of action, and biochemical features of aureochromes.
Zoospores of Chlamydomonas reinhardtii exhibit chemotaxis towards maltose, sucrose, xylose, mannitol, and ammonium. Ten independent mutants defective in chemotaxis towards sugars have been isolated. These mutants form five phenotypic classes. Genetic analysis of two mutant strains defective in chemotaxis to maltose (CHE1, CHE3) and two mutant strains defective in chemotaxis to sucrose (CHE2, CHE4) indicated that the defect in them depended on single nuclear recessive mutant alleles. Mutations mal1, mal2, suc1, and suc2 represent four chemotactic loci that are unlinked to the marker mt located on the linkage group VI. Four loci are unlinked to each other. These observations suggest that the mal and the suc loci do not constitute a spatially single functional group.
Chlorophylls (Chl) are unique tetrapyrrole molecules, essential not only for photosynthesizing organisms but for the whole Biosphere. Chlorophyll biosynthesis is closely connected with plant cell morphogenesis and photosynthetic reactions - storage and transferring of light energy. Pigment mutants of plant and microorganisms are successfully used for investigation of Chl biosynthesis and degradation pathways. The genetic approaches appeared to be very productive for identification of the genes, encoding the enzymes of Chl metabolism and for elucidation of the mechanisms there regulating. History, recent findings and evolution of genetic determination of Chl formation processes are presented in this review.
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