Interactive effects of elevated CO2 and temperature on the leaf-miner Dialectica scalariella Zeller (Lepidoptera: Gracillariidae) in Paterson's Curse, Echium plantagineum (Boraginaceae)

Doubling of the current atmospheric CO₂ concentration, and an increase in global mean annual temperatures of 1.5–6 °C, have been predicted to occur by the end of this century. Whilst the separate effects of CO₂ and temperature on plant–insect interactions have been examined in a number of studies, few have investigated their combined impact. We carried out a factorial experiment to explore the effect of a doubling of CO₂ concentration and a 3 °C temperature increase on the development of a complete generation of the leaf‐miner, Dialectica scalariella, in the host plant Paterson's Curse, Echium plantagineum. Elevated CO₂ increased biomass, reduced leaf N and increased C:N ratios in the host plants. Leaf thickness also increased under elevated CO₂, but only in the high‐temperature treatment. Female D. scalariella did not discriminate between plants grown at the different CO₂ levels when ovipositing, despite the reduction in foliage quality under elevated CO₂. Overall, the negative response of D. scalariella to elevated CO₂ was greater than for many species of free‐living insects, presumably because of the limited mobility imposed by the leaf‐mining habit. Development was accelerated at the high temperature and slowed under elevated CO₂. The net result was a reduction in development time of ～14 days in the elevated CO₂/high temperature treatment, compared to the ambient CO₂/low temperature treatment. Larval survivorship and adult moth weight were both affected by a significant interaction between CO₂ and temperature. At the low temperature, CO₂ had little effect on survivorship, but at the high temperature, survivorship was significantly reduced under elevated CO₂. Similarly, elevated CO₂ had a stronger negative effect on adult moth weight when combined with the high‐temperature treatment. A possible explanation for these results is that the high temperature accelerated insect development to such an extent that the larvae did not have sufficient feeding time to compensate for the poorer quality of the foliage. The frequency with which interactions between CO₂ and temperature affected both plant and insect performance in this study highlights the need for caution when predicting the effects of future climate change on plant–insect interactions from single‐factor experiments.     

Immunohistochemical evidence for the NO cGMP signaling pathway in respiratory ciliated epithelia of rat.

Airway epithelia play a crucial role in protecting the lung from the external environment. Ciliated airway epithelial cells contribute to mucociliary transport systems via ciliary beating and electrolyte transport mechanisms to defend against respiratory tract infection. Both of these activities are regulated by nitric oxide (NO)-dependent mechanisms. To better understand the role of the NO-cGMP signal transduction cascade in these responses, we investigated the localization of endothelial nitric oxide synthase (eNOS), soluble guanylyl cyclase (sGC), cGMP-dependent protein kinase (PKG) I-alpha, and PKG I-beta in the tracheas and lungs of normal rats by immunohistochemistry. Mouse anti-eNOS, rabbit anti-sGC, PKG I-alpha, and PKG I-beta antibodies were used. Strong immunostaining for eNOS was detected in ciliated tracheal, bronchial, and bronchiolar epithelia, in Clara cells, and in Type II alveolar cells. The pattern of sGC and PKG I-beta immunostaining showed striking parallels with that of eNOS staining. No staining was detectable in ciliated epithelium with the anti-PKG I-alpha antibody. Taken together, these observations suggest that PKG I-beta might transduce NO-sGC signaling into biological responses in ciliated respiratory epithelia.(J Histochem Cytochem 47:1369-1374, 1999)     

Reverse engineering the L-type Ca2+ channel alpha1c subunit in adult cardiac myocytes using novel adenoviral vectors

The alpha(1c) subunit of the cardiac L-type Ca(2+) channel, which contains the channel pore, voltage- and Ca(2+)-dependent gating structures, and drug binding sites, has been well studied in heterologous expression systems, but many aspects of L-type Ca(2+) channel behavior in intact cardiomyocytes remain poorly characterized. Here, we develop adenoviral constructs with E1, E3 and fiber gene deletions, to allow incorporation of full-length alpha(1c) gene cassettes into the adenovirus backbone. Wild-type (alpha(1c-wt)) and mutant (alpha(1c-D-)) Ca(2+) channel adenoviruses were constructed. The alpha(1c-D-) contained four point substitutions at amino acid residues known to be critical for dihydropyridine binding. Both alpha(1c-wt) and alpha(1c-D-) expressed robustly in A549 cells (peak L-type Ca(2+) current (I(CaL)) at 0 mV: alpha(1c-wt) -9.94+/-1.00pA/pF, n=9; alpha(1c-D-) -10.30pA/pF, n=12). I(CaL) carried by alpha(1c-D-) was markedly less sensitive to nitrendipine (IC(50) 17.1 microM) than alpha(1c-wt) (IC(50) 88 nM); a feature exploited to discriminate between engineered and native currents in transduced guinea-pig myocytes. 10 microM nitrendipine blocked only 51+/-5% (n=9) of I(CaL) in alpha(1c-D-)-expressing myocytes, in comparison to 86+/-8% (n=9) of I(CaL) in control myocytes. Moreover, in 20 microM nitrendipine, calcium transients could still be evoked in alpha(1c-D-)-transduced cells, but were largely blocked in control myocytes, indicating that the engineered channels were coupled to sarcoplasmic reticular Ca(2+) release. These alpha(1c) adenoviruses provide an unprecedented tool for structure-function studies of cardiac excitation-contraction coupling and L-type Ca(2+) channel regulation in the native myocyte background.     

A low copy number, copia-like transposon in maize.

Bs1, a transposable element that moved into the maize Adh1 gene following barley stripe mosaic virus infection, is shown to be present in 1-5 copies in all maize and teosinte lines tested. Bs1 sequences do not hybridize with the genome of barley stripe mosaic virus. The insertion of Bs1 is bounded by 304-bp perfect direct repeats, similar in structure to Ty1 in yeast, copia and related elements in Drosophila, and vertebrate pro-retroviruses, but different from all other known plant transposons. No free copies of the terminal sequences or large internal deletions of Bs elements could be detected. Bs1 is apparently not related to several transposons which moved into the Shrunken gene in lines made genetically unstable by barley stripe mosaic virus infection, suggesting that this virus may cause genome shock, resulting in a generalized liberation of transposons in response to environmental stress.