Cryptochrome blue light photoreceptors share sequence similarity to photolyases, flavoproteins that mediate light-dependent DNA repair. However, cryptochromes lack photolyase activity and are characterized by distinguishing C-terminal domains. Here we show that the signaling mechanism of Arabidopsis cryptochrome is mediated through the C terminus. On fusion with beta-glucuronidase (GUS), both the Arabidopsis CRY1 C-terminal domain (CCT1) and the CRY2 C-terminal domain (CCT2) mediate a constitutive light response. This constitutive photomorphogenic (COP) phenotype was not observed for mutants of cct1 corresponding to previously described cry1 alleles. We propose that the C-terminal domain of Arabidopsis cryptochrome is maintained in an inactive state in the dark. Irradiation with blue light relieves this repression, presumably through an intra- or intermolecular redox reaction mediated through the flavin bound to the N-terminal photolyase-like domain.

MicroRNAs (miRNAs) are comprised of approximately 21 nucleotide (nt) RNAs that play important regulatory roles in growth and development by targeting mRNAs for cleavage or translational repression. In Arabidopsis, more than one hundred miRNAs have been identified but the biological functions of only a limited number of them have been determined by molecular genetic analysis. miR396 is a miRNA conserved among the dicot and monocot plants. In Arabidopsis, miR396 has two loci (MIR396a and MIR396b) and targets six Growth-Regulating Factor (GRF) genes encoding putative transcription factors with roles in plant leaf growth. Using a northern blot hybridizations approach, we have found that MIR396 is predominantly expressed in leaf and seedling. To further analyze the role of miR396 in the regulation of target genes and leaf growth, we have generated transgenic Arabidopsis plants that constitutively overexpress MIR396a or MIR396b. These transgenic plants have narrow-leaf phenotypes due to reduction in cell number. Ectopic overexpression of MIR396 represses expression of not only six GRF genes but also GIF1 encoding a GRF-interacting transcription coactivator with a role in cell proliferation in leaf. In addition, transgenic MIR396-overexpressing plants have lower densities of stomata and are more tolerant to drought than wild-type plants. These results strongly support the belief that miR396 plays an important role in plant leaf growth and development, most likely by repressing GRF gene expression.

Previous reports have shown a lower proportion of the ACTN3 X/X genotype (R577X nonsense polymorphism) in sprint-related athletes compared to the general population, possibly attributed to impairment of muscle function related to a-actinin-3 deficiency. In the present study, we examined the frequency of the X/X genotype in both Black and White elite-level bodybuilders and strength athletes in comparison to the general population. A reference population of 668 Whites (363 men and 305 women) and 208 Blacks (98 men and 110 women) was genotyped for the ACTN3 R577X polymorphism. Strength athletes (52 white and 23 black; 4 women) consisting predominantly of world class and locally competitive bodybuilders, and elite powerlifters were recruited and similarly genotyped. Significantly lower X/X genotype frequencies were observed in the athletes (6.7%) vs controls (16.3%; P ¼ 0.005). The X/X genotype was significantly lower in White athletes (9.7%) vs controls (19.9%; P ¼ 0.018). No black athletes (0%) were observed with the X/X genotype, though this finding only approached statistical significance vs controls (4.8%; P ¼ 0.10). The results indicate that the ACTN3 R577X nonsense allele (X) is underrepresented in elite strength athletes, consistent with previous reports indicating that a-actinin-3 deficiency appears to impair muscle performance.

The direct preparation of grafting polymer brushes from commercial poly (vinylidene fluoride) (PVDF) films with surface‐initiated atom transfer radical polymerization (ATRP) is demonstrated. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the hydrophilic monomers from the PVDF surface. Homopolymer brushes of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMAEMA) and poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the PVDF surface. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and atomic force microscopy. A kinetic study revealed a linear increase in the graft concentration of poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (PDMAEMA) and poly[poly(ethylene glycol) monomethacrylate] (PPEGMA) with the reaction time, indicating that the chain growth from the surface was consistent with a controlled or living process. The living chain ends were used as macroinitiators for the synthesis of diblock copolymer brushes. The water contact angles on PVDF films were reduced by the surface grafting of DMAEMA and PEGMA. Protein adsorption experiments revealed a substantial antifouling property of PPEGMA‐grafted PVDF films and PDMAEMA‐grafted PVDF films in comparison with the pristine PVDF surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3434–3443, 2006