Circadian clock adjustment to plant iron status depends on chloroplast and phytochrome function

Plant chloroplasts are not only the main cellular location for storage of elemental iron (Fe), but also the main site for Fe, which is incorporated into chlorophyll, haem and the photosynthetic machinery. How plants measure internal Fe levels is unknown. We describe here a new Fe‐dependent response, a change in the period of the circadian clock. In Arabidopsis, the period lengthens when Fe becomes limiting, and gradually shortens as external Fe levels increase. Etiolated seedlings or light‐grown plants treated with plastid translation inhibitors do not respond to changes in Fe supply, pointing to developed chloroplasts as central hubs for circadian Fe sensing. Phytochrome‐deficient mutants maintain a short period even under Fe deficiency, stressing the role of early light signalling in coupling the clock to Fe responses. Further mutant and pharmacological analyses suggest that known players in plastid‐to‐nucleus signalling do not directly participate in Fe sensing. We propose that the sensor governing circadian Fe responses defines a new retrograde pathway that involves a plastid‐encoded protein that depends on phytochromes and the functional state of chloroplasts.     

First descriptions of Coelometopini pupae (Coleoptera: Tenebrionidae) from Australia,Southeast Asia and the Pacific region,with comments on phylogenetic relationships and antipredator adaptations

Abstract. The pupal stage of ten Coelometopini species occurring in Australia, New Guinea, Southeast Asia and the Pacific region are described and a key for their identification is provided. The species are Chrysopeplus expolitus Broun, Derosphaerus hirtipes Kaszab, Hypaulax crenata (Boisduval), Leprocaulus borneensis Kaszab, Metisopus purpureipennis Bates, Promethis carteri Kaszab, P. nigra (Blessig), P. quadraticollis (Gebien), P. quadricollis Pascoe and P. sulcigera (Boisduval). The gin trap structures of D. hirtipes and P. quadraticollis are described in detail using scanning electron micrographs. A summary of antipredator structures of all known Coelometopini pupae is given. The phylogenetic value of pupal characters is assessed at intra‐ and intergeneric levels within the tribe.     

Evidence for a dual mechanism of chick embryo fibroblast adhesion on fibronectin and laminin substrata

Eight-day-old chick embryo fibroblasts were shown to adhere specifically to fibronectin and laminin substrata. Moreover, the Scatchard analysis reveals 540,000 binding sites per cell for the fibronectin with a dissociation constant (Kd) of 1.35 microM and 5,500 binding sites per cell for laminin with a Kd of 1.5 nM. Furthermore, cell-fibronectin interactions are mediated by plasma membrane proteins of high molecular weight (HMW) (150K and 125K) insensitive to trypsin treatment and low molecular weight (LMW) proteins (95K, 80K, 65K and 45K) sensitive to trypsin treatment. Adhesion of 8-day-old chick embryo fibroblasts on laminin is mediated by plasma membrane proteins highly sensitive to trypsin treatment. Regarding the paucity of laminin-binding sites, the identification of laminin receptor could not be achieved. Nevertheless, this study provides quantitative and qualitative evidences for different mechanisms of 8-day-old chick embryo fibroblasts on laminin and fibronectin.     

A yeast protein analogous to Escherichia coli RecA protein whose cellular level is enhanced after UV irradiation

Summary In Saccharomyces cerevisiae, a protein was recognized by polyclonal antibodies raised against homogeneous Escherichia coli K12 RecA protein. The cellular level of the yeast protein called RecAsc (molecular weight 44 kDa, pI 6.3), was transiently enhanced after UV irradiation. Protease inhibitors were required to minimize degradation of the RecAsc protein during cell lysis. The RecAsc protein exhibited similar basal levels and similar kinetics of increase after UV irradiation in DNA-repair proficient (RAD ⁺) strains carrying mitochondrial DNA or not (rho ⁰). This was also true for the following DNA-repair deficient (rad ^-) strains: rad2-6 rad6-1 rad52-1, a triple mutant blocked in three major repair pathways; rad6-, a mutant containing an integrative deletion in a gene playing a central role in mutagenesis; pso2-1, a mutant that exhibits a reduced rate of mutagenesis and recombination after exposure to DNA cross-linking agents.     

Thermography as a predictive tool for laser treatment of port-wine stains

The argon laser, which has been proven both useful and safe for port-wine stain therapy, interacts with the hemoglobin of the vessels. In a percentage of cases, this treatment is still inefficient, and there is a lack of correlation between these bad results and clinical or histologic criteria. Thermography, which explores the vascularization of the port-wine stain, leads us to consider port-wine stains from a physical point of view. This very simple test shows no correlation with the clinical parameters of port-wine stain but is closely related to the results obtained with laser therapy. It seems to be a good criterion to estimate the argon laser treatment prognosis.     

Metabolic,physiological and kinetic aspects of the alcoholic fermentation of whey permeate by Kluyveromyces fragilis NRRL 665 and Kluyveromyces lactis NCYC 571

Optimum growth conditions for the fermentation of non-concentrated whey permeate by Kluyveromyces fragilis NRRL 665 have been defined. Use of 3.75 g yeast extract l^?1, a growth temperature of 38°C and a pH of 4.0 allowed a maximum productivity of 5.23 g ethanol l^?1 h^?1 in continuous culture with a yield 91% of theoretical. Complete batch fermentation of permeate with 100 g lactose l^?1 was possible with a maximum specific growth rate of 0.276 h^?1 without any change in ethanol yield. Fermentation of concentrated permeate resulted, however, in a general decrease of specific substrate consumption rate, demonstrated by the inability to completely convert an initial 90 or 150 g lactose l^?1 in continuous culture, even at dilution rates as low as 0.05 and 0.08 h^?1, respectively. The decrease could be related to substrate inhibition, to an increase in osmotic pressure caused by lactose and salts, and to ethanol inhibition of both alcohol and biomass yield. The decrease in specific productivity could be counterbalanced by use of high cell density cultures, obtained by cell recycle of K. fragilis. Fermentation of a non-concentrated permeáte at a dilution rate of 1 h^?1 resulted in a productivity of 22 g l^?1 h^?1 at 22 g ethanol l^?1. Cell recycle using flocculating Kluyveromyces lactis NCYC 571 was also tested. With this strain a productivity of 9.3 g l^?1 h^?1 at 45 g product l^?1 was attained at a dilution rate of 0.2 h^?1, with an initial lactose concentration of 95 g l^?1.     

Binding of 5-methoxypsoralen to human serum low density lipoproteins

5-methoxypsoralen (5-MOP) binds to human serum low density lipoproteins (LDL) according to a two-step process. Scatchard analysis of the first step yields K = 1.4 × 10⁵ M^?1 and 4 binding sites. It involves the LDL apoprotein. The second step corresponds to a solubilization, in the lipidic core, of ? 45 molecules of 5MOP per LDL molecule. It is accompanied by a large blue shift of the 5MOP fluorescence. The ability of LDL to bind 5MOP and to carry it into various cells may explain some biological effects sometimes encountered during PUVA therapy.     

Plasmid-mediated resistance to fosfomycin in Staphylococcus epidermidis

Staphylococcus epidermidis strain BM2641, isolated from a patient, was resistant to penicillin G, methicillin, aminoglycosides, chloramphenicol, macrolide, lincosamide and streptogramin B-type (MLS) antibiotics, and to high levels of fosmycin. Resistance to forsfomycin and/or to MLS was lost at low frequencies either spontaneously or after curing with novobiocin. The plasmid DNA from BM2641 and its cured derivatives was purified, analyzed by agarose gel electrophoresis and transferred to a nitrocellulose sheet. Comparative analysis of the resistance phenotypes with the plasmid content of the strains indicated that fosfomycin and MLS resistance were encoded by plasmids pIP1842 (2.5 kb) and pIP1843 (2.6 kb), respectively. Southern hybridization with a probe specific for gene fosA of Serratia marcescens showed that the fosfomycin resistance determinant in Staphylococcus is not homologous to that of Gram-negative bacteria.