The Role of Cryptochrome 1 and Phytochromes in the Control of Plant Photomorphogenetic Responses to Green Light

We studied the role of cryptochrome 1 (CRY1) and phytochromes in the photomorphogenetic responses of plants to the middle-wavelength region of photosynthetically active radiation. A comparison was performed of green light (GL) action on growth, GA activity and IAA and ABA contents during seedling deetiolation of two Arabidopsis thaliana (L.) Heynh lines of Landsnerg erecta ecotype (wild type Ler and mutant hy4) and of Phaseolus vulgaris L. It was shown that a growth responses of Ler hypocotyls to GL of 515 nm and Ler cotyledons to GL of 542 nm were weaker than those of the hy4 mutant defected in the CRY1 synthesis. Far-red light (730 nm) neutralized the effect of GL (533 nm) on the phytohormone balance in the primary kidney bean leaves. The data obtained permit a supposition that plants possess several photoregulatory systems functioning under GL of higher (515 nm) and lower emission energy (542–553 nm). A possible operation of GL receptors, other than cryptochrome 1 and phytochromes, is discussed.     

On the Mechanism of Action of <Emphasis Type="Italic">lac</Emphasis> Repressor

Chen et al. have proved conclusively that lac repressor and RNA polymerase bind independently to wild type lac DNA in vitro. To explain the lacp ^s mutation, which causes competitive binding between repressor and polymerase, they suggest that a new promoter site has been created near the lac operator.     

Phenotypic effects of genetic variability in human clock genes on circadian and sleep parameters

Circadian rhythms and sleep are two separate but intimately related processes. Circadian rhythms are generated through the precisely controlled, cyclic expression of a number of genes designated clock genes. Genetic variability in these genes has been associated with a number of phenotypic differences in circadian as well as sleep parameters, both in mouse models and in humans. Diurnal preferences as determined by the selfreported Horne-Östberg (HÖ) questionnaire, has been associated with polymorphisms in the human genes CLOCK, PER1, PER2 and PER3. Circadian rhythm-related sleep disorders have also been associated with mutations and polymorphisms in clock genes, with the advanced type cosegrating in an autosomal dominant inheritance pattern with mutations in the genes PER2 and CSNK1D, and the delayed type associating without discernible Mendelian inheritance with polymorphisms in CLOCK and PER3. Several mouse models of clock gene null alleles have been demonstrated to have affected sleep homeostasis. Recent findings have shown that the variable number tandem polymorphism in PER3, previously linked to diurnal preference, has profound effects on sleep homeostasis and cognitive performance following sleep loss, confirming the close association between the processes of circadian rhythms and sleep at the genetic level.