KIBRA is a novel substrate for protein kinase Czeta

WW domain-containing proteins are found in all eukaryotic cells and they are involved in the regulation of a wide variety of cellular functions. We recently identified the neuronal protein KIBRA as novel member of this family of signal transducers. In this report, we describe the identification of protein kinase C (PKC) zeta as a KIBRA-interacting protein. PKCzeta is known to play an important role in synaptic plasticity and memory formation but its specific targets are not well known. Our studies presented here revealed that KIBRA is a novel substrate for PKCzeta and suggest that PKCzeta phosphorylation may regulate the cellular function of KIBRA.     

Lack of adverse effects in pregnant/lactating female rats and their offspring following pre- and postnatal exposure to ELF magnetic fields

We have recently reported that exposure of pregnant rats to 60 Hz at field strengths up to 0.5 mT during the entire period of pregnancy did not induce any biologically significant effects on both pregnant dams and embryo-fetal development. The present study was carried out to investigate the potential effects of gestational and lactational MF exposure on pregnancy, delivery, and lactation of dams and growth, behavior, and mating performance of their offspring in rats. Timed-pregnant female Sprague-Dawley (SD) rats (24/group) received continuous exposure to 60 Hz magnetic field (MF) at field strengths of 0 (sham control), 5 microT, 83.3 microT, or 0.5 mT. Dams received MF or sham exposures for 21 h/day from gestational day 6 through lactational day 21. Experimentally generated MF was monitored continuously throughout the study. No exposure-related changes in clinical signs, body weight, food consumption, pregnancy length, and necropsy findings were observed in dams. Parameters of growth, behavior, and reproductive performance of offspring showed no changes related to MF exposure. There were no adverse effects on embryo-fetal development of F2 offspring from dams exposed to MF. In conclusion, exposure of pregnant SD rats to 60 Hz at field strengths up to 0.5 mT from gestational day 6 to lactational day 21 did not produce biologically significant effects in dams, F1 offspring, or F2 fetuses.     

Arabidopsis ALF4 encodes a nuclear-localized protein required for lateral root formation

Lateral root formation, the primary way plants increase their root mass, displays developmental plasticity in response to environmental changes. The aberrant lateral root formation (alf)4-1 mutation blocks the initiation of lateral roots, thus greatly altering root system architecture. We have positionally cloned the ALF4 gene and have further characterized its phenotype. The encoded ALF4 protein is conserved among plants and has no similarities to proteins from other kingdoms. The gene is present in a single copy in Arabidopsis. Using translational reporters for ALF4 gene expression, we have determined that the ALF4 protein is nuclear localized and that the gene is expressed in most plant tissues; however, ALF4 expression and ALF4's subcellular location are not regulated by auxin. These findings taken together with further genetic and phenotypic characterization of the alf4-1 mutant suggest that ALF4 functions independent from auxin signaling and instead functions in maintaining the pericycle in the mitotically competent state needed for lateral root formation. Our results provide genetic evidence that the pericycle shares properties with meristems and that this tissue plays a central role in creating the developmental plasticity needed for root system development.     

寄生植物锁阳茎的发育解剖学研究

锁阳茎的初生分生组织由原表皮、基本分生组织以及在基本分生组织中呈波浪式环状排列的原形成层束组成。茎的增粗是由于呈波浪式环状排列的维管束,其“波浪”上下幅度逐渐增大,即从“浪”的基部到“浪”顶端维管束数目由4个逐渐增加到10－12个。维管束数目不断增加是由于：（1）由髓射线薄壁细胞反分化产生分生组织束,分生组织束活动产生新的维管束;（2）维管束中分化出一列或几列薄壁细胞,导致该维管束被分化出的薄壁细胞分成2－3个独立的维管束。     

Plasticity in structure and interactions is critical for the action of indolicidin,an antibacterial peptide of innate immune origin

The comparative analysis of two cationic antibacterial peptides of the cathelicidin family-indolicidin and tritrypticin-enabled addressing the structural features critical for the mechanism of indolicidin activity. Functional behavior of retro-indolicidin was found to be identical to that of native indolicidin. It is apparent that the gross conformational propensities associated with retro-peptides resemble those of the native sequences, suggesting that native and retro-peptides can have similar structures. Both the native and the retro-indolicidin show identical affinities while binding to endotoxin, the initial event associated with the antibacterial activity of cationic peptide antibiotics. The indolicidin-endotoxin binding was modeled by docking the indolicidin molecule in the endotoxin structure. The conformational flexibility associated with the indolicidin residues, as well as that of the fatty acid chains of endotoxin combined with the relatively strong structural interactions, such as ionic and hydrophobic, provide the basis for the endotoxin-peptide recognition. Thus, the key feature of the recognition between the cationic antibacterial peptides and endotoxin is the plasticity of molecular interactions, which may have been designed for the purpose of maintaining activity against a broad range of organisms, a hallmark of primitive host defense.     

Speciation and the establishment of zonation in an intertidal barnacle: specific settlement vs. selection

The tropical barnacle Tetraclita forms a belt on hard substrates in the intertidal zone of the Red Sea. Based on morphological data, three distinct species were suggested to exist, occupying different vertical levels - T. barnesorum, T. rufotincta and T. achituvi. In this study we used molecular (12S mitochondrial ribosomal DNA) and ecological data to examine whether this morphological variability reflects genetic differences, or is a result of environmental factors. Adults and spats, collected from settlement plates, were censused and screened genotypically using single strand conformation polymorphism (SSCP) analysis, and settlement dynamics was recorded. We provide evidence for the existence of only two distinct species, and point out both phenotypic plasticity and convergence within and between the proposed species. Cyprids of T. achituvi settle specifically at the lower part of the Tetraclita belt, and feature one phenotype. In contrast, T. rufotincta, occupying the upper and middle portions of the Tetraclita belt, settles throughout the range, shows phenotypic plasticity (three variants), and presumably undergoes selection at the lower part. Thus, the vertical zonation of Tetraclita is produced by the combination of pre-settlement and post-settlement factors, in T. achituvi and T. rufotincta, respectively. The examined system may offer a model in which to study the mechanisms underlying sympatric speciation.     

Biochemical signaling networks decode temporal patterns of synaptic input

Synapses exhibit a wide repertoire of responses to different temporal patterns of synaptic input. Many of these responses are expressed as short and long-term changes in synaptic strength. Electrical properties of channels and calcium buildup can account for rapid aspects of pattern decoding, but it is not clear how more complex input patterns, especially those lasting over many minutes, could be discriminated. This paper shows that a network of signaling pathways can discriminate between complex input patterns lasting tens of minutes, and can give rise to distinct combinatorial patterns of biochemical signaling activity in pathways involved in synaptic change. Regulatory signaling input can alter and even reverse the strengths of responses to input patterns. Thus the synaptic signaling network may function as a temporal decoder that transforms patterns from the time domain into the domain of chemical signaling. This may underlie different synaptic responses to different stimulus patterns.Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1019644427655     

New principles of cell plasticity

Recent discoveries demonstrating surprising cell plasticity in animals and humans call into question many long held assumptions regarding differentiative potential of adult cells. These assumptions reflect a classical paradigm of cell lineage development projected onto both prenatal development and post-natal maintenance and repair of tissues. The classical paradigm describes unidirectional, hierarchical lineages proceedings step-wise from totipotent or pluripotent stem cells through intermediate, ever more restricted progenitor cells, leading finally to 'terminally differentiated' cells. However, in light of both the recent discoveries and older clinical or experimental findings, we have suggested principles comprising a new paradigm of cell plasticity, summarized here.     

Participation of CaMKII in neuronal plasticity and memory formation

1. The unique biochemical properties of Ca²⁺/calmodulin (CaM)-dependent protein kinase II have made this enzyme one of the paradigmatic models of the forever searched memory molecule.2. In particular, the central participation of CaMKII as a sensor of the Ca²⁺ signals generated by activation of NMDA receptors after the induction of long-term plastic changes, has encouraged the use of pharmacological, genetic, biochemical, and imaging tools to unveil the role of this kinase in the acquisition, consolidation, and expression of different types of memories.3. Here we review some of the more exciting discoveries related to the mechanisms involved in CaMKII activation and synaptic plasticity.