Cell division in <Emphasis Type="Italic">Escherichia coli</Emphasis>cultures monitored at single cell resolution

Background  

A fundamental characteristic of cells is the ability to divide. To date, most parameters of bacterial cultures, including cell division, have been measured as cell population averages, assuming that all bacteria divide at a uniform rate.     

Homology modeling of major intrinsic proteins in rice,maize and <Emphasis Type="Italic">Arabidopsis</Emphasis>: comparative analysis of transmembrane helix association and aromatic/arginine selectivity filters

Background  

The major intrinsic proteins (MIPs) facilitate the transport of water and neutral solutes across the lipid bilayers. Plant MIPs are believed to be important in cell division and expansion and in water transport properties in response to environmental conditions. More than 30 MIP sequences have been identified in Arabidopsis thaliana, maize and rice. Plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), Nod26-like intrinsic protein (NIPs) and small and basic intrinsic proteins (SIPs) are subfamilies of plant MIPs. Despite sequence diversity, all the experimentally determined structures belonging to the MIP superfamily have the same "hour-glass" fold.     

Physiological Roles of Brassinosteroids in Early Growth of <Emphasis Type="Italic">Arabidopsis:</Emphasis> Brassinosteroids Have a Synergistic Relationship with Gibberellin as well as Auxin in Light-Grown Hypocotyl Elongation

We examined the physiological effects of brassinosteroids (BRs) on early growth of Arabidopsis. Brassinazole (Brz), a BR biosynthesis inhibitor, was used to elucidate the significance of endogenous BRs. It inhibited growth of roots, hypocotyls, and cotyledonous leaf blades dose-dependently and independent of light conditions. This fact suggests that endogenous BRs are necessary for normal growth of individual organs of Arabidopsis in both photomorphogenetic and skotomorphogenetic programs. Exogenous brassinolide (BL) promoted hypocotyl elongation remarkably in light-grown seedlings. Cytological observation disclosed that BL-induced hypocotyl elongation was achieved through cell enlargement rather than cell division. Furthermore, a serial experiment with hormone inhibitors showed that BL induced hypocotyl elongation not through gibberellin and auxin actions. However, a synergistic relationship of BL with gibberellin A₃ (GA₃) and indole-3-acetic acid (IAA) was observed on elongation growth in light-grown hypocotyls, even though gibberellins have been reported to be additive to BR action in other plants. Taken together, our results show that BRs play an important role in the juvenile growth of Arabidopsis; moreover, BRs act on light-grown hypocotyl elongation independent of, but cooperatively with, gibberellins and auxin.     

Identification of the <Emphasis Type="Italic">C. elegans</Emphasis>anaphase promoting complex subunit Cdc26 by phenotypic profiling and functional rescue in yeast

Background  

RNA interference coupled with videorecording of C. elegans embryos is a powerful method for identifying genes involved in cell division processes. Here we present a functional analysis of the gene B0511.9, previously identified as a candidate cell polarity gene in an RNAi videorecording screen of chromosome I embryonic lethal genes.     

An efficient <Emphasis Type="Italic">Foxtail mosaic virus</Emphasis> vector system with reduced environmental risk

Background  

Plant viral vectors offer high-yield expression of pharmaceutical and commercially important proteins with a minimum of cost and preparation time. The use of Agrobacterium tumefaciens has been introduced to deliver the viral vector as a transgene to each plant cell via a simple, nonsterile infiltration technique called "agroinoculation". With agroinoculation, a full length, systemically moving virus is no longer necessary for excellent protein yield, since the viral transgene is transcribed and replicates in every infiltrated cell. Viral genes may therefore be deleted to decrease the potential for accidental spread and persistence of the viral vector in the environment.     

The distinctive cell division interactome of <Emphasis Type="Italic">Neisseria gonorrhoeae</Emphasis>

Background

Bacterial cell division is an essential process driven by the formation of a Z-ring structure, as a cytoskeletal scaffold at the mid-cell, followed by the recruitment of various proteins which form the divisome. The cell division interactome reflects the complement of different interactions between all divisome proteins. To date, only two cell division interactomes have been characterized, in Escherichia coli and in Streptococcus pneumoniae. The cell divison proteins encoded by Neisseria gonorrhoeae include FtsZ, FtsA, ZipA, FtsK, FtsQ, FtsI, FtsW, and FtsN. The purpose of the present study was to characterize the cell division interactome of N. gonorrhoeae using several different methods to identify protein-protein interactions. We also characterized the specific subdomains of FtsA implicated in interactions with FtsZ, FtsQ, FtsN and FtsW.

Results

Using a combination of bacterial two-hybrid (B2H), glutathione S-transferase (GST) pull-down assays, and surface plasmon resonance (SPR), nine interactions were observed among the eight gonococcal cell division proteins tested. ZipA did not interact with any other cell division proteins. Comparisons of the N. gonorrhoeae cell division interactome with the published interactomes from E. coli and S. pneumoniae indicated that FtsA-FtsZ and FtsZ-FtsK interactions were common to all three species. FtsA-FtsW and FtsK-FtsN interactions were only present in N. gonorrhoeae. The 2A and 2B subdomains of FtsA_Ng were involved in interactions with FtsQ, FtsZ, and FtsN, and the 2A subdomain was involved in interaction with FtsW.

Conclusions

Results from this research indicate that N. gonorrhoeae has a distinctive cell division interactome as compared with other microorganisms.

     

A canonical FtsZ protein in <Emphasis Type="Italic">Verrucomicrobium spinosum</Emphasis>, a member of the Bacterial phylum <Emphasis Type="Italic">Verrucomicrobia</Emphasis> that also includes tubulin-producing <Emphasis Type="Italic">Prosthecobacter</Emphasis> species

Background  

The origin and evolution of the homologous GTP-binding cytoskeletal proteins FtsZ typical of Bacteria and tubulin characteristic of eukaryotes is a major question in molecular evolutionary biology. Both FtsZ and tubulin are central to key cell biology processes – bacterial septation and cell division in the case of FtsZ and in the case of tubulins the function of microtubules necessary for mitosis and other key cytoskeleton-dependent processes in eukaryotes. The origin of tubulin in particular is of significance to models for eukaryote origins. Most members of domain Bacteria possess FtsZ, but bacteria in genus Prosthecobacter of the phylum Verrucomicrobia form a key exception, possessing tubulin homologs BtubA and BtubB. It is therefore of interest to know whether other members of phylum Verrucomicrobia possess FtsZ or tubulin as their FtsZ-tubulin gene family representative.     

Caspase inhibitors affect the kinetics and dimensions of tracheary elements in xylogenic Zinnia (<Emphasis Type="Italic">Zinnia elegans</Emphasis>) cell cultures

Background  

The xylem vascular system is composed of fused dead, hollow cells called tracheary elements (TEs) that originate through trans-differentiation of root and shoot cambium cells. TEs undergo autolysis as they differentiate and mature. The final stage of the formation of TEs in plants is the death of the involved cells, a process showing some similarities to programmed cell death (PCD) in animal systems. Plant proteases with functional similarity to proteases involved in mammalian apoptotic cell death (caspases) are suggested as an integral part of the core mechanism of most PCD responses in plants, but participation of plant caspase-like proteases in TE PCD has not yet been documented.     

Brassinosteroid-mediated stress tolerance in Arabidopsis shows interactions with abscisic acid,ethylene and salicylic acid pathways

Background  

Brassinosteroids (BRs) play crucial roles in plant development and also promote tolerance to a range of abiotic stresses. Although much has been learned about their roles in plant development, the mechanisms by which BRs control plant stress responses and regulate stress-responsive gene expression are not fully known. Since BR interacts with other plant hormones, it is likely that the stress tolerance conferring ability of BR lies in part in its interactions with other stress hormones.     

Significance of Cuscutain,a cysteine protease from <Emphasis Type="Italic">Cuscuta reflexa</Emphasis>, in host-parasite interactions

Background  

Plant infestation with parasitic weeds like Cuscuta reflexa induces morphological as well as biochemical changes in the host and the parasite. These modifications could be caused by a change in protein or gene activity. Using a comparative macroarray approach Cuscuta genes specifically upregulated at the host attachment site were identified.     

Rapid and dynamic subcellular reorganization following mechanical stimulation of <Emphasis Type="Italic">Arabidopsis</Emphasis>epidermal cells mimics responses to fungal and oomycete attack

Background  

Plant cells respond to the presence of potential fungal or oomycete pathogens by mounting a basal defence response that involves aggregation of cytoplasm, reorganization of cytoskeletal, endomembrane and other cell components and development of cell wall appositions beneath the infection site. This response is induced by non-adapted, avirulent and virulent pathogens alike, and in the majority of cases achieves penetration resistance against the microorganism on the plant surface. To explore the nature of signals that trigger this subcellular response and to determine the timing of its induction, we have monitored the reorganization of GFP-tagged actin, microtubules, endoplasmic reticulum (ER) and peroxisomes inArabidopsis plants – after touching the epidermal surface with a microneedle.     

Cloning and characterization of a 9-lipoxygenase gene induced by pathogen attack from <Emphasis Type="Italic">Nicotiana benthamiana</Emphasis>for biotechnological application

Background  

Plant lipoxygenases (LOXs) have been proposed to form biologically active compounds both during normal developmental stages such as germination or growth as well as during responses to environmental stress such as wounding or pathogen attack. In our previous study, we found that enzyme activity of endogenous 9-LOX in Nicotiana benthamiana was highly induced by agroinfiltration using a tobacco mosaic virus (TMV) based vector system.     

Crucial role of zebrafish <Emphasis Type="Italic">prox1</Emphasis>in hypothalamic catecholaminergic neurons development

Background  

Prox1, the vertebrate homolog of prospero in Drosophila melanogaster, is a divergent homeogene that regulates cell proliferation, fate determination and differentiation during vertebrate embryonic development.     

The evolution of transposable elements in natural populations of self-fertilizing <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> and its outcrossing relative <Emphasis Type="Italic">Arabidopsis lyrata</Emphasis>

Background  

Transposable Elements (TEs) make up the majority of plant genomes, and thus understanding TE evolutionary dynamics is key to understanding plant genome evolution. Plant reproductive systems are diverse and mating type variation is one factor among many hypothesized to influence TE evolutionary dynamics. Here, we collected a large TE-display data set in self-fertilizing Arabidopsis thaliana, and compared it to data gathered in outcrossing Arabidopsis lyrata. We analyzed seven TE families in four natural populations of each species to tease apart the effects of mating system, demography, transposition, and selection in determining patterns of TE diversity.