Differential Responses of Abaxial and Adaxial Guard Cells of Broad Bean to Abscisic Acid and Calcium1

Regulation by abscisic acid (ABA) and Ca2+ of broad bean (Vicia faba) abaxial and adaxial guard cell movements and inward K+ currents were compared. One millimolar Ca2+ in the bathing medium inhibited abaxial stomatal opening by 60% but only inhibited adaxial stomatal opening by 15%. The addition of 1 μm ABA in the bathing medium resulted in 80% inhibition of abaxial but only 45% inhibition of adaxial stomatal opening. Similarly, ABA and Ca2+ each stimulated greater abaxial stomatal closure than adaxial stomatal closure. Whole-cell patch-clamp results showed that the inward K+ currents of abaxial guard cells were inhibited by 60% (−180 mV) in the presence of 1.5 μm Ca2+ in the cytoplasm, whereas the inward K+ currents of adaxial guard cells were not affected at all by the same treatment. Although 1 μm ABA in the cytoplasm inhibited the inward K+ currents to a similar extent for both abaxial and adaxial guard cells, the former were more sensitive to ABA applied externally. These results suggest that the abaxial stomata are more sensitive to Ca2+ and ABA than adaxial stomata in regard to stomatal opening and closing processes and that the regulation of the inward K+ currents by ABA may not proceed via a Ca2+-signaling pathway in adaxial guard cells. Therefore, there may be different pathways for ABA- and Ca2+-mediated signal transduction in abaxial and adaxial guard cells.

The role of haustoria in sugar supply during infection of broad bean by the rust fungus Uromyces fabae

Biotrophic plant pathogenic fungi differentiate specialized infection structures within the living cells of their host plants. These haustoria have been linked to nutrient uptake ever since their discovery. We have for the first time to our knowledge shown that the flow of sugars from the host Vicia faba to the rust fungus Uromyces fabae seems to occur largely through the haustorial complex. One of the most abundantly expressed genes in rust haustoria, the expression of which is negligible in other fungal structures, codes for a hexose transporter. Functional expression of the gene termed HXT1 in Saccharomyces cerevisiae and Xenopus laevis oocytes assigned a substrate specificity for d-glucose and d-fructose and indicated a proton symport mechanism. Abs against HXT1p exclusively labeled haustoria in immunofluorescence microscopy and the haustorial plasma membrane in electron microscopy. These results suggest that the fungus concentrates this transporter in haustoria to take advantage of a specialized compartment of the haustorial complex. The extrahaustorial matrix, delimited by the plasma membranes of both host and parasite, constitutes a newly formed apoplastic compartment with qualities distinct from those of the bulk apoplast. This organization might facilitate the competition of the parasite with natural sink organs of the host.

ATP-dependent uptake of natural product cytotoxic drugs by membrane vesicles establishes MRP as a broad specificity transporter.

MRP is a recently isolated ATP-binding cassette family transporter. We previously reported transfection studies that established that MRP confers multidrug resistance [Kruh, G. D., Chan, A., Myers, K., Gaughan, K., Miki, T. & Aaronson, S. A. (1994) Cancer Res. 54, 1649-1652] and that expression of MRP is associated with enhanced cellular efflux of lipophilic cytotoxic agents [Breuninger, L. M., Paul, S., Gaughan, K., Miki, T., Chan, A., Aaronson, S. A. & Kruh, G. D. (1995) Cancer Res. 55, 5342-5347]. To examine the biochemical mechanism by which MRP confers multidrug resistance, drug uptake experiments were performed using inside-out membrane vesicles prepared from NIH 3T3 cells transfected with an MRP expression vector. ATP-dependent transport was observed for several lipophilic cytotoxic agents including daunorubicin, etoposide, and vincristine, as well as for the glutathione conjugate leukotriene C4 (LTC4). However, only marginally increased uptake was observed for vinblastine and Taxol. Drug uptake was osmotically sensitive and saturable with regard to substrate concentration, with Km values of 6.3 microM, 4.4 microM, 4.2 microM, 35 nM, and 38 microM, for daunorubicin, etoposide, vincristine, LTC4, and ATP, respectively. The broad substrate specificity of MRP was confirmed by the observation that daunorubicin transport was competitively inhibited by reduced and oxidized glutathione, the glutathione conjugates S-(p-azidophenacyl)-glutathione (APA-SG) and S-(2,4-dinitrophenyl)glutathione (DNP-SG), arsenate, and the LTD4 antagonist MK571. This study establishes that MRP pumps unaltered lipophilic cytotoxic drugs, and suggests that this activity is an important mechanism by which the transporter confers multidrug resistance. The present study also indicates that the substrate specificity of MRP is overlapping but distinct from that of P-glycoprotein, and includes both the neutral or mildly cationic natural product cytotoxic drugs and the anionic products of glutathione conjugation. The widespread expression of MRP in tissues, combined with its ability to transport both lipophilic xenobiotics and the products of phase II detoxification, indicates that the transporter represents a widespread and remarkably versatile cellular defense mechanism.

Broad resistance to plant viruses in transgenic plants conferred by antisense inhibition of a host gene essential in S-adenosylmethionine-dependent transmethylation reactions.

S-Adenosylhomocysteine hydrolase (SAHH) is a key enzyme in transmethylation reactions that use S-adenosylmethionine as the methyl donor. Because of the importance of SAHH in a number of S-adenosylmethionine-dependent transmethylation reactions, particularly the 5' capping of mRNA during viral replication, SAHH has been considered as a target of potential antiviral agents against animal viruses. To test the possibility of engineering a broad type of resistance to plant viruses, we expressed the antisense RNA for tobacco SAHH in transgenic tobacco plants. As expected, transgenic plants constitutively expressing an anti-sense SAHH gene showed resistance to infection by various plant viruses. Among those plants, about half exhibited some level of morphological change (typically stunting). Analysis of the physiological change in those plants showed that they contained excess levels of cytokinin. Because cytokinin has been found to induce acquired resistance, there is also a strong possibility that the observed resistance was induced by cytokinin.

A bottomless pit: the costs of Crimea’s annexation by Russia. OSW Commentary No. 143, 29.07.2014

The annexation of Crimea has brought the Russian authorities significant dividends, in particular on the domestic stage: it has resulted in an unprecedented social and political consolidation, and strengthened Vladimir Putin’s position after several years of decline in social support for him. It has provided Russia with strategic benefits, giving it broad access to the Black Sea and the military infrastructure on the peninsula, as well as access to natural gas and crude oil reserves. Russia has also taken over numerous assets (including the tourist infrastructure) previously owned by the Ukrainian state. However, the decision itself concerning Moscow’s annexation of Crimea was taken off the cuff, with no calculation of the costs of integrating it with the Russian legal, political and socio-economic space. Russia took over a region that required subsidies from the Ukrainian budget; moreover, the annexation struck at the most important industry of the Crimean economy – tourism. Crimea’s integration with Russia will be a complex process that entails high costs, financial, organisational and social, including multi-billion dollar investments in the modernisation and development of infrastructure, covering the region’s budget deficit, and paying out social benefits. For reasons of prestige and political significance, Moscow is treating Crimea as a showcase region. Russia is determined to prove that the Crimean incorporation will be beneficial for the region’s economy and will raise people’s living standards. However, the expenses triggered by Crimea’s integration will coincide with a deteriorating economic situation in Russia, aggravated by US and EU sanctions, and this may force Russia to postpone or even give up some of its ambitious investments in the peninsula. Some of the integration costs will have to be borne by other Russian regions, even though they already face serious financial problems that have forced them to reduce their own investment programs. Another issue that has come into question is the fulfilment of the Crimean people’s’ expectations concerning the improvement of their living standards, due to the tourist sector’s problems (small-scale tourist services used to be one of the local people’s main sources of income), the rising costs of maintenance, and finally, restrictions of civil rights after the introduction of the more restrictive Russian legislation.

What do Eurozone academics think about EMU reform? On broad support and German exceptionalism. Bruges Political Research Papers 41/2015.

This paper is an empirical contribution to the literature on the formation of policy preferences on Economic and Monetary Union (EMU) reform within its Member States. In the aftermath of the euro crisis, many proposals to ‘complete’ EMU have been tabled. However, discord among Member States has led to a piecemeal restructuring of EMU. For this paper, a survey has been conducted among euro area academic experts, gauging preferences on EMU reform. We find that general consensus masks significant discord among academics from different Member States. Our data indicates the existence of conflicting national epistemic communities, bound by shared causal beliefs on macro-economic policy. Academics within the key creditor Member State, Germany, assume an outlier position. Within the sample of German academics, economists are particularly strongly opposed to all moves in the direction of fiscal or social union. As economists are those academic experts most likely to influence the economic policy beliefs dominant among the German policy elite, these results are highly politically salient. We confront these findings with the literature on the exceptionalism of German economics. We contend that our results substantiate the claim that inadequate EMU reform and, more generally, the EU approach to the Eurozone crisis, can be partially explained by the firm grip these economic doctrines hold over the economics profession and policy-making circles in Germany.

Safety belts: the uncollected dividends. A manual for use by state legislators and state officials on techniques to increase safety belt usage. Final report.

National Highway Traffic Safety Administration, Washington, D.C.