Antisense inhibition of the sucrose transporter in potato: effects on amount and activity

The sucrose proton-cotransporter gene from potato (StSUT1) is mainly expressed in the phloem of mature, exporting leaves. To study the in vivo role of the protein, potato plants were transformed with antisense constructs of the sucrose transporter cDNA under control of the CaMV35S and the rolC promoters, respectively. Both types of transgenic plant develop symptoms characteristic of an inhibition of phloem loading. To determine the level of inhibition, immunological and transport studies were performed. Purified antibodies directed against a peptide from the central loop of SUT1 recognized a transporter with an apparent molecular mass of 47 kDa in leaf plasma membrane vesicles. Antisense repression under control of the non-specific CaMV35S promoter led to a strong reduction in SUT1 protein, whereas no such reduction could be detected when the companion cell-specific rolC promoter was used. Similarily. sucrose uptake in plasma membrane vesicles was reduced by 50–75% in CaMV35S but not in rolC plants. These data suggest that, unlike the rolC promoter, the sucrose transporter is expressed not only in the companion cells but also in other leaf cells. However, inhibition of the transporter by rolC-controlled antisense repression is sufficient to impair phloem loading.     

Abnormal extracellular matrix and excessive growth of human adult polycystic kidney disease epithelia.

Human autosomal dominant polycystic kidney disease (ADPKD) epithelia were grown in primary monolayer cultures and their properties compared with intact kidney epithelial cultures derived from individually microdissected normal human kidney proximal convoluted tubules (PCT), proximal straight tubules (PST), and cortical collecting tubules (CCT). In vivo, ADPKD cyst epithelia exhibited a thickened basement membrane, and immunofluorescence demonstrated the presence of laminin, fibronectin, type IV collagen, and heparan sulfate proteoglycan in basement membranes and type I collagen in the interstitium. ADPKD epithelia grown in culture synthesized and secreted basally a unique, extracellular matrix that took the form of proteinaceous spheroids when the cells were grown on dried, type I collagen. Incorporation of H2[S35O4] into basement membrane extracts was increased more than ten-fold in ADPKD epithelia by comparison to normal PST and CCT. In addition to incorporation into the normal tubular basement membrane 220 kD band, radioactivity was also seen at 175 kD and 150 kD in ADPKD extracts. Growth in culture of cyst-lining ADPKD epithelia was more rapid than normal tubules, and was abnormal since there was no absolute requirement for added extracellular matrix. However, when ADPKD epithelia were grown on different, exogenous matrix protein components, a profound influence on both structure and epithelial cell proliferation was seen. Growth on a complete basement membrane three-dimensional gel derived from the Engelbreth-Holm-Swarm (EHS) sarcoma led to a reduction in the numbers of spheroids and increase in amorphous filaments. Incorporation of [3H]-thymidine into ADPKD epithelia was greater than into normal PCT, PST, and CCT and was also greatly modified by the type of extracellular matrix components provided. In studies using single matrix components, the strongest proliferative response was seen when ADPKD epithelia were plated on type I collagen greater than type IV collagen greater than fibronectin greater than laminin. These findings suggest that the excessive growth of cyst-lining epithelia may be, at least in part, a result of abnormal basement membrane and extracellular matrix production by ADPKD cells.     

Genetic linkage studies of autosomal dominant polycystic kidney disease: search for the second gene in a large Sicilian family

Summary Polycystic kidney disease (PKD) is a common autosomal dominant genetic disorder caused by mutation in at least two different gene loci. The PKD1 gene has been localized on the short arm of chromosome 16. The location of a second genetic locus in the human genome is not yet known. A large PKD kindred, unlinked to chromosome 16, with over 250 members was studied using both DNA and classical markers. In total, 29 informative marker loci on 11 autosomes have been analyzed for linkage with PKD. The data significantly exclude the linkage with disease locus from 17 marker loci and show no evidence of close linkage with the other loci.     

Aging exacerbates damage and delays repair of alveolar epithelia following influenza viral pneumonia

Background

Influenza virus infection causes significantly higher levels of morbidity and mortality in the elderly. Studies have shown that impaired immunity in the elderly contributes to the increased susceptibility to influenza virus infection, however, how aging affects the lung tissue damage and repair has not been completely elucidated.

Methods

Aged (16–18 months old) and young (2–3 months old) mice were infected with influenza virus intratracheally. Body weight and mortality were monitored. Different days after infection, lung sections were stained to estimate the overall lung tissue damage and for club cells, pro-SPC⁺ bronchiolar epithelial cells, alveolar type I and II cells to quantify their frequencies using automated image analysis algorithms.

Results

Following influenza infection, aged mice lose more weight and die from otherwise sub-lethal influenza infection in young mice. Although there is no difference in damage and regeneration of club cells between the young and the aged mice, damage to alveolar type I and II cells (AT1s and AT2s) is exacerbated, and regeneration of AT2s and their precursors (pro-SPC-positive bronchiolar epithelial cells) is significantly delayed in the aged mice. We further show that oseltamivir treatment reduces virus load and lung damage, and promotes pulmonary recovery from infection in the aged mice.

Conclusions

These findings show that aging increases susceptibility of the distal lung epithelium to influenza infection and delays the emergence of pro-SPC positive progenitor cells during the repair process. Our findings also shed light on possible approaches to enhance the clinical management of severe influenza pneumonia in the elderly.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0116-z) contains supplementary material, which is available to authorized users.     

Application of transgenic plants in understanding responses to atmospheric change

Acclimation of plants to an increase in atmospheric carbon dioxide concentration is a well described phenomenon. It is characterized by an increase in leaf carbohydrates and a degradation of ribulose 1, 5-bisphosphate carboxylase protein (Rubisco) leading in the long term to a lower rate of CO₂ assimilation than expected from the kinetic constants of Rubisco. This article summarizes studies with transgenic plants grown in elevated pCO₂ which are modified in their capacity of CO₂ fixation, of sucrose and starch synthesis, of triosephosphate and sucrose transport and of sink metabolism of sucrose. These studies show that a feedback accumulation of carbohydrates in leaves play only a minor role in acclimation, because leaf starch synthesis functions as an efficient buffer for photoassimilates. There is some evidence that in elevated pCO₂, plants grow faster and senescence is induced earlier.     

Companion cell-specific inhibition of the potato sucrose transporter SUT1

In many plants, translocation of sucrose from mesnsophyll to phloem for long-distance transport is carrier-mediated. The sucrose H⁺-symporter gene SUT1 from potato is expressed at high levels in the phloem of mature, exporting leaves and at lower levels in other organs. Inhibition of SUT1 by expression of an antisense gene in companion cells under control of the rolC promoter leads to accumulation of high amounts of soluble and insoluble carbohydrates in leaves and inhibition of photosynthesis. The distribution of in situ localized starch does not correspond with areas of reduced photosynthesis as shown by fluorescence imaging. Dissection of antisense effects on sink and source organs by reciprocal grafts shows that inhibition of transporter gene expression in leaves is sufficient to produce chlorosis in leaves and reduced tuber yield. In contrast to the arrest of plasmodesmal development found in plants that express yeast invertase in the apoplast, in mature leaves of sucrose transporter antisense plants plasmodesmata are branched and have median cavities. These data strongly support an apoplastic mode of phloem loading in potato, in which the sucrose transporter located at the plasma membrane of the sieve element/companion cell complex represents the primary route for sugar uptake into the long-distance translocation pathway.     

Chronic exposure of diesel exhaust particles induces alveolar enlargement in mice

Background

Diesel exhaust particles (DEPs) are deposited into the respiratory tract and are thought to be a risk factor for the development of diseases of the respiratory system. In healthy individuals, the timing and mechanisms of respiratory tract injuries caused by chronic exposure to air pollution remain to be clarified.

Methods

We evaluated the effects of chronic exposure to DEP at doses below those found in a typical bus corridor in Sao Paulo (150 μg/m³). Male BALB/c mice were divided into mice receiving a nasal instillation: saline (saline; n = 30) and 30 μg/10 μL of DEP (DEP; n = 30). Nasal instillations were performed five days a week, over a period of 90 days. Bronchoalveolar lavage (BAL) was performed, and the concentrations of interleukin (IL)-4, IL-10, IL-13 and interferon-gamma (INF-γ) were determined by ELISA-immunoassay. Assessment of respiratory mechanics was performed. The gene expression of Muc5ac in lung was evaluated by RT-PCR. The presence of IL-13, MAC2+ macrophages, CD3+, CD4+, CD8+ T cells and CD20+ B cells in tissues was analysed by immunohistochemistry. Bronchial thickness and the collagen/elastic fibers density were evaluated by morphometry. We measured the mean linear intercept (Lm), a measure of alveolar distension, and the mean airspace diameter (D0) and statistical distribution (D2).

Results

DEP decreased IFN-γ levels in BAL (p = 0.03), but did not significantly alter IL-4, IL-10 and IL-13 levels. MAC2+ macrophage, CD4+ T cell and CD20+ B cell numbers were not altered; however, numbers of CD3+ T cells (p ≤ 0.001) and CD8+ T cells (p ≤ 0.001) increased in the parenchyma. Although IL-13 (p = 0.008) expression decreased in the bronchiolar epithelium, Muc5ac gene expression was not altered in the lung of DEP-exposed animals. Although respiratory mechanics, elastic and collagen density were not modified, the mean linear intercept (Lm) was increased in the DEP-exposed animals (p ≤ 0.001), and the index D2 was statistically different (p = 0.038) from the control animals.

Conclusion

Our data suggest that nasal instillation of low doses of DEP over a period of 90 days results in alveolar enlargement in the pulmonary parenchyma of healthy mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0172-z) contains supplementary material, which is available to authorized users.     

A set of multiplex panels of microsatellite markers for rapid molecular characterization of rice accessions

Background  

This study aimed to analyze the efficiency of three new microsatellite multiplex panels, which were designed to evaluate a total of 16 loci of the rice genome, based on single PCR reactions of each panel. A sample of 548 accessions of traditional upland rice landraces collected in Brazil in the last 25 years was genotyped, a database of allelic frequencies was established, estimates of genetic parameters were performed and analysis of genetic structure of the collection was developed.