Penaeus monodon chitin-binding protein (PmCBP) is involved in white spot syndrome virus (WSSV) infection

White spot syndrome virus (WSSV) can cause the most serious viral disease of shrimp and has a wide host range among crustaceans. Although researches show a lot about its genome and structure, information concerning the mechanism of how WSSV infects' cells is lacking. In this study, some experiments were applied to confirm the biological meaning of the protein–protein interaction between WSSV envelope protein, VP53A, and Penaeus monodon chitin-binding protein (PmCBP). Immunofluorescent study indicated that PmCBP is located on the cell surface of host cells. PmCBP amounts of about 34 kDa can be detected in both P. monodon and Litopenaeus vannamei tissues by Western blotting. In the in vivo neutralization experiment, both rVP53A and rPmCBP that were produced by Esherichia coli can promote resp. a 40% and 20% survival rate of the shrimp which were challenged by WSSV. Furthermore, a yeast-two-hybrid result revealed that PmCBP could interact with at least 11 WSSV envelope proteins. Those findings suggest that PmCBP may be involved in WSSV infection.     

Nucleocytoplasmic transit of human α1‐antichymotrypsin in tobacco leaf epidermal cells†

Recently, we have observed a nuclear localization for human α₁‐antichymotrypsin (AACT) expressed in the cytosol of transgenic Bright Yellow‐2 (BY‐2) tobacco cultured cells (see accompanying paper: Benchabane, M., Saint‐Jore‐Dupas, C., Bardor, M., Faye, L., Michaud, D. and Gomord, V. (2008a) Targeting and post‐translational processing of human α₁‐antichymotrypsin in BY‐2 tobacco cultured cells. Plant Biotechnol. J. doi: 10.1111/j.1467‐7652.2008.00382.x). In the present article, we assess whether the intrinsic DNA‐binding activity of AACT can explain its nuclear localization, and whether this same activity has an impact on its protease inhibitory potency and stability in planta. An engineered form of AACT with no DNA‐binding activity, rAACTΔK, was compared with the wild‐type polypeptide, rAACT, in terms of chymotrypsin inhibitory potency, stability in planta and distribution in tobacco cells. In accordance with available data reporting distinct sites for protease inhibition and DNA binding, rAACT and rAACTΔK showed similar antichymotrypsin activity, similar to the activity of native AACT purified from human plasma. As observed for AACT in BY‐2 tobacco cells, a green fluorescent protein (GFP)‐AACT fusion transiently expressed in the cytosol of tobacco leaf epidermal cells was detected mainly in the nucleus by confocal laser microscopy. By contrast, rAACTΔK expressed as a GFP fusion showed a balanced distribution between the cytosol and the nucleus, similar to the distribution pattern of free GFP exhibiting no DNA‐binding affinity. In line with immunodetection data showing higher accumulation levels for GFP‐AACT in tobacco leaf cells, rAACTΔK was more susceptible than rAACT to tryptic digestion in the presence of DNA. Overall, these observations suggest the following: (i) a retention effect of DNA on AACT in the nucleus; and (ii) a stabilizing effect of the AACT–DNA interaction on rAACT challenged with non‐target proteases, which, possibly, may be useful in protecting this protein in plant expression platforms.     

The nucleolus： reviewing oldies to have new understandings

The nucleolus is the most prominent compartment in the nucleus and known as the site for ribosome biogenesis ineucaryotes.In contrast,there is no such equivalent structure for ribosome synthesis in procaryotes.This raises twoconcerns that how does the nucleolus evolve and that whether the nucleolus remains playing a single role in ribosomebiogenesis along the evolution.Increasing data support new nucleolus functions,including signal recognition particleassembly,small RNA modification,telomerase maturation,cell-cycle and aging control,and cell stress sensor.Multiplefunctions of the nucleolus possibly result from the plurifunctionality of nucleolar proteins,such as nucleolin and Nopp 140.Proteomic analyses of human and Arabidopsis nucleolus lead a remarkable progress in understanding the evolution andnew functions of nucleoli.In this review,we present a brief history of nucleolus research and new concepts and unre-solved questions.Also,we introduce hepatitis D virus for studying the communication between the nucleolus and othersubnuclear compartments,and Caenorhabditis elegans for the role of nucleolus in the development and the epistaticcontrol of nucleologenesis.     

Enhanced Mutation Rate,Relaxed Selection,and the “Domino Effect” are associated with Gene Loss in Blattabacterium,A Cockroach Endosymbiont

Intracellular endosymbionts have reduced genomes that progressively lose genes at a timescale of tens of million years. We previously reported that gene loss rate is linked to mutation rate in Blattabacterium, however, the mechanisms causing gene loss are not yet fully understood. Here, we carried out comparative genomic analyses on the complete genome sequences of a representative set of 67 Blattabacterium strains, with sizes ranging between 511 and 645 kb. We found that 200 of the 566 analyzed protein-coding genes were lost in at least one lineage of Blattabacterium, with the most extreme case being one gene that was lost independently in 24 lineages. We found evidence for three mechanisms influencing gene loss in Blattabacterium. First, gene loss rates were found to increase exponentially with the accumulation of substitutions. Second, genes involved in vitamin and amino acid metabolism experienced relaxed selection in Cryptocercus and Mastotermes, possibly triggered by their vertically inherited gut symbionts. Third, we found evidence of epistatic interactions among genes leading to a “domino effect” of gene loss within pathways. Our results highlight the complexity of the process of genome erosion in an endosymbiont.     

Estimating root elongation rates from morphological measurements of the root tip

To measure the elongation rate of individual roots in soil remains a challenge. A novel method for estimating elongation rates of excavated roots is presented. Morphological markers are identified along the tip of excavated roots, and their distance relative to the apex is measured. These markers correspond to developmental stages which follow known temporal patterns. Hence, their distance relative to the apex reflects root elongation during the period corresponding to their development. The method was tested on maize roots grown in a range of conditions and substrates. It was found that distances from markers to apices were proportional, with some variability, to elongation rates. Remarkably, the linear relationships between these distances were neither affected by substrate, nor by growing conditions. Using several markers allows covering time periods ranging from 0.3 day to 3 days as well as cross validation of estimates. Provided further testing, under a wider range of environmental conditions, is conducted, the concepts presented in this paper may serve to define a new measurement technique.     

DART: a software to analyse root system architecture and development from captured images

Image analysis is used in numerous studies of root system architecture (RSA). To date, fully automatic procedures have not been good enough to completely replace alternative manual methods. DART (Data Analysis of Root Tracings) is freeware based on human vision to identify roots, particularly across time-series. Each root is described by a series of ordered links encapsulating specific information and is connected to other roots. The population of links constitutes the RSA. DART creates a comprehensive dataset ready for individual or global analyses and this can display root growth sequences along time. We exemplify here individual tomato root growth response to shortfall in solar radiation and we analyse the global distribution of the inter-root branching distances. DART helps in studying RSA and in producing structured and flexible datasets of individual root growth parameters. It is written in JAVA and relies on manual procedures to minimize the risks of errors and biases in datasets.     

A tracheomycosis as a tool for studying the impact of stem xylem dysfunction on leaf water status and gas exchange in Citrus aurantium L.

Permanent xylem blockage is a common result of attacks by herbivores and fungi. The mitosporic fungus Phoma tracheiphila (Petri) Kantschaveli et Gikachvili, is the agent of a Citrus tracheomycosis (“malsecco disease”) causing xylem impairment and leading to leaf shedding and plant dieback. In the present study, this pathogen was used for monitoring the effects of increasing levels of stem hydraulic resistance (R _stem) on leaf water status and gas exchange. In this view, measurements are reported of changes in the hydraulic resistance of infected stems (R _stem) of C. aurantium (sour orange) during progressive and irreversible xylem blockage with parallel measurements of leaf water potential and conductance to water vapour. Leaves were highly responsive to increasing R _stem as due to fungal infection, with substantial stomatal closure and drop in water potential.