[Analysis of dominant-recessive mutated character of nfr genes of Chlamydomonas reinhardtii and its mutual interaction with the chloroplastic psbA gene].

Phenotypic analysis of the nfr/Nfr diplontic hybrids has demonstrated the recessive mutated character of the nfr genes, and the norflurazon resistant character of the Nfr-4 And Nfr-5 mutants were resulted in by the different nuclear genes nfr-1 and nfr-2 respectively. From the tetrad analysis result of hybridizations of psbA mutant with wild strains CC-124 and nfr mutant, it have been demonstrated that the sensitivity of psbA mutated strain to norflurazon under photoautotrophic condition is due to its multiple effect whereas the chloroplast genome under the mixotrophic situation also gives some effect for resistance to norflurazon. From the titration results of cross-resistant character for antibiotics of norflurazon resistant strains, we had found that, the Nfr-3 mutant has some cross-resistance to erythromycin and streptomycin; based on this phenomenon it would be expected that this mutant having resistant character to suppressor of phytoene desaturase also give some effect for construction of chloroplastic protein.

Photoreceptor current and photoorientation in chlamydomonas mediated by 9-demethylchlamyrhodopsin.

Green flagellates possess rhodopsin-like photoreceptors involved in control of their behavior via generation of photocurrents across the plasma membrane. Chlamydomonas mutants blocked in retinal biosynthesis are "blind," but they can be rescued by the addition of exogenous retinoids. Photosignaling by chlamyrhodopsin regenerated with 9-demethylretinal was investigated by recording photocurrents from single cells and cell suspensions, and by measuring phototactic orientation. The addition of a saturating concentration of this analog led to reconstitution of all receptor molecules. However, sensitivity of the photoreceptor current in cells reconstituted with the analog was smaller compared with retinal-reconstituted cells, indicating a decreased signaling efficiency of the analog receptor protein. Suppression of the photoreceptor current in double-flash experiments was smaller and its recovery faster with 9-demethylretinal than with retinal, as it would be expected from a decreased PC amplitude in the analog-reconstituted cells. Cells reconstituted with either retinal or the analog displayed negative phototaxis at low light and switched to positive one upon an increase in stimulus intensity, as opposed to the wild type. The reversal of the phototaxis direction in analog-reconstituted cells was shifted to a higher fluence rate compared with cells reconstituted with retinal, which corresponded to the decreased signaling efficiency of 9-demethylchlamyrhodopsin.

[Genetic characterization of subcbnI genes of Chlamydomonas reinhardtii].

Fourteen different revertants of Chlamydomonas reinhardtii recovered with ability of biosynthesis chlorophyll b were hybridized with wile-type strain, and tetrad analysis with random sampling was performed. It appeared that sub genes resulting in cbnI gene to reverse mutation, and localize on the first chromosome. According to its linkage that differences, 5 strains carrying various mutant alleles of suppressor genes were determined. Forward hybridological analysis demonstrated that the sub genes were absent of allelic specificity and had a single genic character in response to suppression. Phenotypic analysis of the sub/Sub diplontic hybrid have verified the dominant character of mutant sub genes. The phenomenon of present various allelic sub genes and all its characters revealed that the possibility of several ways or various regulatory means exists in biosynthesis of chlorophyll b.

Accumulation of ζ-carotene in Chlamydomonas reinhardtii under control of the ac5 nuclear gene.

The accumulation of different precursors of carotenoid biosynthesis in carotenoid-deficient mutants of Chlamydomonas reinhardtii was studied by HPLC-analysis. ζ-Carotene accumulated in several ac5 mutants, this character cosegregated with mutations in the ac5 gene. Two groups of ac5 mutants differing in ζ-carotene accumulation were distinguished. One (ac5-1) accumulated ζ-carotene in the dark but not in the light. The other (ac5-2) accumulated ζ-carotene under both dark and light conditions. ac5-2 strains accumulated more ζ-carotene in the dark than ac5-1 strains. Genetic data suggested that the mutations ac5-1 and ac5-2 were allelic. Pleiotropic effects of mutations in the ac5 gene included decreased levels of chlorophyll a and b and acetate requirement. The results are consistent with the presence of a defective ζ-carotene desaturase in ac5 mutants.

[The Petergof genetic collection of microorganisms]. / Petergofskie geneticheskie kollektsii mikroorganizmov.

The Petergof Genetic Collection (PGC) of microalgae was created in the 1960s during study of the regularities of mutational processes. A collection of yeasts has been maintained at the Department of Genetics and Selection of St. Petersburg State University since 1977. This collection contains some 1000 genetically marked strains of the yeasts Saccharomyces cerevisiae and Pichia methanolica, and the algae collection comprises about 600 strains of Chlamydomonas reinhardtii, Chlorella vulgaris, and Scenedesmus obliquus. The structure of the collection and the employment of strains in basic and applied research, as well as for educational purposes, are discussed. On the basis of the original software GENESTRAIN, a yeast PGC database (DB) was developed. A visual interface that contains information about selection of Ch. reinhardtii strains and crosses made was created in the HyperCard operational system.

The detection and characterization of G-proteins in the eyespot of Chlamydomonas reinhardtii.

The presence of G-proteins in the eyespot fraction of Chlamydomonas reinhardtii is shown. This fraction is capable of binding (GTP gamma[35S], possesses the GTPase activity and interacts with antibodies raised against a highly conserved peptide of most G-proteins' alpha-subunit. Cross-reaction with a 24-kDa protein is detected on immunoblots. Using an antiserum prepared from vertebrate beta-subunit peptide, two additional proteins with apparent Mr 21 and 29 kDa could be revealed. The light-dependence of GTPase extraction from eyespot membranes is shown. The results make it possible to suggest the participation of G-proteins in the photosensory transduction chain of Ch. reinhardtii.

[Photodimerization of uracil in films and their use for dosimetry of genetically active ultraviolet irradiation]. / Fotodimerizatsiia uratsila v plenkakh i vozmozhnosti ee primeneniia dlia dozimetrii geneticheski aktivnogo ul'trafioletovogo izlucheniia.

On the basis of the known photodimerization of uracil it is proposed to use its films obtained by sublimation in vacuum for the dosimetry of genetically active UV radiation. Experimental estimations are presented of radiation dose rate resulting in a change of uracil optical density delta D/D0 under irradiation due to photodimerization for erythemal lamp lo-30. The data obtained are used for dosimetry of lethal damage of Chlamydomonas reinhardii. Estimations are also presented of the sun radiation dose rate which induce uracil photodimerization on the earth surface and in the extraterrestrial atmosphere.

[Study of primary photoprocesses in photosystem II of Chlamydomonas mutant strains by hole-burning spectroscopy]. / Issledovanie pervichnykh fotoprotsessov v fotosisteme 2 mutantov khlamidomonady metodom spektroskopii vyzhiganiia provalov.

The method of hole-burning in absorption spectra at helium temperatures has been applied to the study of primary photoprocesses in photosystem II (PS2) of Chlamydomonas reinhardii mutant strains 420/7 and N-154. The former is enriched in PS2 reaction centers (the chlorophyll a/P680 ratio is about of 50--70) and the latter presumably lacks the pheophytin molecule which is the primary electron acceptor in PS2. For the strain 420/7 samples with ferricyanide addition two types of holes have been observed differing in their width and spectral region of burning. One type could be burned in the region of 678--682 nm (P680 is responsible for burning) and another one -- in the region of 682--688 nm (pheophytin is responsible). The excited states relaxation times evaluated from the hole widths are 3,8 +/- 0,8 ps for P680 and 9,8 +/- 1.5 ps for pheophytin. The new mechanism of PS2 operating has been proposed in which photoexcited phenophytin molecule functions as a primary electron donor. In the case of N-154 strain the only type of holes has been observed for which P680 is responsible. The excited state relaxation time of the latter evaluated from the hole width is 10 +/- 2 ps.

[Spectroscopic study of "hole burning" of the initial photoprocesses in photosystem I of mutant strain Chlamydomonas reinhardii 516-3a enriched with P700 reaction centers]. / Issledovanie metodom spektroskopii "vyzhiganiia provalov" pervichnykh fotoprotsessov v fotosisteme 1 mutantnogo shtamma Chlamydomonas reinhardii 516-3a, obogashchennogo reaktsionnymi tsentrami P700.

The effect of "hole burning" in absorption spectrum upon monochromatic illumination at 4.2 degrees K has been investigated on the Chlamydomonas reinhardii mutant strain 516-3a which possesses the chlorophyll a/P700 ratio of about 25. This effect has been earlier discovered for the wild type strain of Chlorella. In the strain 516-3a two types of holes differing in width and in shape have been observed. For their assignment the maximal (saturated) holewidth has been studied as a function of the burning wavelength. It has been shown that for the holes of one type photooxidation of P700 is responsible. The other type of holes is caused by electrochromic transition shift of another component of the reaction centre with the absorption maximum at 693 nm. Using measured holewidths it has been estimated that the lifetime of P700 excited state is not less than 50 ps and that the excited state lifetime of the component responsible for the other type of holes is 8.6 ps. The latter, in assumption that it is limited by energy transfer between two components under consideration, gives a distance of 20 A between them. Possible reasons of disagreement between obtained P700* lifetime and considerably shorter times attributed earlier to the primary electron phototransfer in photosystem I on the basis of picosecond studies are discussed.

["Burning" of troughs in the low-temperature absorption spectra of a strain of Chlamydomonas reinhardii enriched by P700]. / Vyzhiganie provalov v nizkotemperaturnykh spektrakh pogloshcheniia shtamma Chlamydomonas reinhardii, imeiushchego obogashchenie po P700.

Spectral and photochemical parameters were described of the mutant strain of Chlamydomonas reinhardii 516--3a, in which the ratio chlorophyll a/P700 is about 20. Experiments were carried out with this strain for investigating earlier observed for Chlorella effect of burning out of deeps in absorption spectra at 4.2K resulting from irradiation with monochromatic light of the wavelength 698 nm. Arguments are presented in favour of the assumption that phototransformation of P700 is responsible for the formation of deeps. It has been found from the width of the deeps that the lifetime of the excited states of the centres responsible for the formation of deeps is between 16 ps and 65 ps.