Lhca5 – an LHC-Type Protein Associated with Photosystem I

The light-harvesting antenna of higher plant photosystem (PS) I is known to be composed of four different types of light-harvesting complex (LHC) proteins (Lhca1-4). However, the genomic sequence of Arabidopsis thaliana contains open reading frames coding for two additional LHC type proteins (Lhca5-6) that are presumably associated with PSI. While Lhca6 might not be expressed at all, ESTs have been detected for the Lhca5 gene in Arabidopsis and a number of other plant species. Here we demonstrate the presence of the Lhca5 gene product in the thylakoid membrane of Arabidopsis as an additional type of Lhca-protein associated with PSI. Lhca5 seems to be regulated differently from the other LHC proteins since Lhca5 mRNA levels increase under high light conditions. Analyses reported here of Lhca5 in plants lacking individual Lhca1-4 proteins show that it is more abundant in plants lacking Lhca1/4, and suggest that it interacts in a direct physical fashion with Lhca2 or Lhca3. We propose that Lhca5 binds chlorophylls in a similar fashion to the other Lhca proteins and is associated with PSI only in sub-stoichiometric amounts.     

Oxidative decomposition of vitamin C in drinking water

We have previously shown that vitamin C (ascorbic acid) can initiate hydroxyl radical formation in copper contaminated household drinking water. In the present study, we have examined the stability of vitamin C in copper and bicarbonate containing household drinking water. In drinking water samples, contaminated with copper from the pipes and buffered with bicarbonate, 35% of the added vitamin C was oxidized to dehydroascorbic acid within 15 min. After 3 h incubation at room temperature, 93% of the added (2 mM) ascorbic acid had been oxidized. The dehydroascorbic acid formed was further decomposed to oxalic acid and threonic acid by the hydrogen peroxide generated from the copper (I) autooxidation in the presence of oxygen. A very modest oxidation of vitamin C occurred in Milli-Q water and in household water samples not contaminated by copper ions. Moreover, addition of vitamin C to commercially sold domestic bottled water samples did not result in vitamin C oxidation. Our results demonstrate that ascorbic acid is rapidly oxidized to dehydroascorbic acid and further decomposed to oxalic- and threonic acid in copper contaminated household tap water that is buffered with bicarbonate. The impact of consuming ascorbic acid together with copper and bicarbonate containing drinking water on human health is discussed.     

Antisense inhibition of the photosynthetic antenna proteins CP29 and CP26: implications for the mechanism of protective energy dissipation

The specific roles of the chlorophyll a/b binding proteins CP29 and CP26 in light harvesting and energy dissipation within the photosynthetic apparatus have been investigated. Arabidopsis was transformed with antisense constructs against the genes encoding the CP29 or CP26 apoprotein, which gave rise to several transgenic lines with remarkably low amounts of the antisense target proteins. The decrease in the level of CP24 protein in the CP29 antisense lines indicates a physical interaction between these complexes. Analysis of chlorophyll fluorescence showed that removal of the proteins affected photosystem II function, probably as a result of changes in the organization of the light-harvesting antenna. However, whole plant measurements showed that overall photosynthetic rates were similar to those in the wild type. Both antisense lines were capable of the qE type of nonphotochemical fluorescence quenching, although there were minor changes in the capacity for quenching and in its induction kinetics. High-light-induced violaxanthin deepoxidation to zeaxanthin was not affected, although the pool size of these pigments was decreased slightly. We conclude that CP29 and CP26 are unlikely to be sites for nonphotochemical quenching.     

Structure of the O-polysaccharide from the lipopolysaccharide from Vibrio cholerae O6

The O-polysaccharide from Vibrio cholerae O6 was isolated from the LPS by mild-acid hydrolysis and has been investigated by sugar and methylation analysis and NMR spectroscopy. The polysaccharide was also depolymerized with aqueous hydrofluoric acid to give the repeating unit and multiples thereof. The O-polysaccharide had the following tetrasaccharide repeating unit. Two O-acetyl groups are present, one of them making the GlcNAc residue fully substituted and the steric crowding considerable at the branching residue.     

Intracerebroventricular interleukin-6 treatment decreases body fat in rats

Recently we found that interleukin-6 (IL-6) knockout mice develop mature-onset obesity and that a single intracerebroventricular (ICV) injection of IL-6 increases energy expenditure. In the present study we investigated if chronic ICV treatment with IL-6 can suppress body fat mass. IL-6 was injected ICV daily for two weeks to rats fed a high-fat diet. IL-6 treatment but not saline treatment decreased body weight by 8.4% and decreased the relative weights of mesenteric and retroperitoneal fat pads. Consistent with this, circulating leptin levels were decreased by 40% after IL-6 treatment but not after saline treatment. Average food intake per day was decreased in the IL-6 treated group compared to the saline treated rats. IL-6 treatment did not change hepatic expression of the acute-phase protein haptoglobin, serum levels of insulin or insulin-like growth factor-I, or the weights of the heart, liver, kidneys, adrenals, and spleen. We conclude that centrally administered IL-6 can decrease body fat in rats without causing acute-phase reaction.     

Pro-active management of beet armyworm (Lepidoptera: Noctuidae) resistance to tebufenozide and methoxyfenozide: baseline monitoring,risk assessment,and isolation of resistance

Susceptibility to tebufenozide and methoxyfenozide of beet armyworm [Spodoptera exigua (Hübner)] from the southern United States and Thailand was determined through exposure of first and third instars to dipped cotton leaves. Among the field populations evaluated, tebufenozide LC50 values for first and third instars, respectively, ranged from 0.377 to 4.41 and 4.37-46.6 microg (AI) /ml of solution. Methoxyfenozide LC50 values for first and third instars of field populations ranged from 0.058 to 0.487 and 0.601-3.83 microg (AI)/ml of solution. A Thailand field strain exhibiting reduced susceptibility to both compounds was subjected to intense laboratory selection for three nonconsecutive generations. At the LC50 and LC90, selected Thailand strains were 45-68 times and 150-1,500 times less susceptible to tebufenozide and 340-320 times and 120-67 times less susceptible to methoxyfenozide as first and third instars, respectively, when compared with the laboratory reference strain. Among the U.S. field populations evaluated, ones from Belle Glade, FL, and Florence, SC, were generally the most susceptible and ones from Maricopa and Parker, AZ, were the least susceptible. Selection of the Thailand field strain with tebufenozide reduced susceptibility to both compounds, and selection of Thailand strains previously pressured with either compound further reduced susceptibility to both, suggesting at least some commonality of resistance mechanism. Characterization of this resistance will provide information that will be helpful for pro-active management of resistance for this valuable group of insecticides.     

Gene expression in autumn leaves

Two cDNA libraries were prepared, one from leaves of a field-grown aspen (Populus tremula) tree, harvested just before any visible sign of leaf senescence in the autumn, and one from young but fully expanded leaves of greenhouse-grown aspen (Populus tremula x tremuloides). Expressed sequence tags (ESTs; 5,128 and 4,841, respectively) were obtained from the two libraries. A semiautomatic method of annotation and functional classification of the ESTs, according to a modified Munich Institute of Protein Sequences classification scheme, was developed, utilizing information from three different databases. The patterns of gene expression in the two libraries were strikingly different. In the autumn leaf library, ESTs encoding metallothionein, early light-inducible proteins, and cysteine proteases were most abundant. Clones encoding other proteases and proteins involved in respiration and breakdown of lipids and pigments, as well as stress-related genes, were also well represented. We identified homologs to many known senescence-associated genes, as well as seven different genes encoding cysteine proteases, two encoding aspartic proteases, five encoding metallothioneins, and 35 additional genes that were up-regulated in autumn leaves. We also indirectly estimated the rate of plastid protein synthesis in the autumn leaves to be less that 10% of that in young leaves.     

Circulating monocytes from healthy individuals and COPD patients

Background

Chronic obstructive pulmonary disease (COPD) is characterized by incompletely reversible airflow obstruction associated with inflammation in which monocytes/macrophages are the predominant inflammatory cells. The only known genetic factor related to COPD is inherited PiZZ deficiency of α1-antitrypsin (AAT), an inhibitor of serine proteases.

Methods

We investigated the basal and LPS-stimulated release of pro-inflammatory molecules from blood monocytes isolated from age and gender matched healthy (n = 30) and COPD (n = 20) individuals with and without AAT deficiency.

Results

After 18 h of cell culture the basal release of MMP-9 was 2.5-fold, p < 0.02 greater, whereas IL-8 was 1.8-fold (p < 0.01) lower from COPD patient monocytes than from controls. LPS-stimulated release of IL-6 and MCP-1 was greater from COPD patient's monocytes relative to controls, while activation of control cells resulted in enhanced secretion of ICAM-1 and MMP-9 compared to COPD patients. Independent of disease status, monocytes from PiZZ AAT carriers released less TNFα (by 2.3-fold, p < 0.03).

Conclusions

The basal and LPS-stimulated secretion of specific pro-inflammatory molecules from circulating monocytes differs between healthy and COPD subjects. These findings may be valuable for further studies on the mechanisms involved in recruitment and activation of inflammatory cells in COPD.