Mi-1-Mediated Nematode Resistance in Tomatoes is Broken by Short-Term Heat Stress but Recovers Over Time

Tomato (Solanum lycopersicum L.) is among the most valuable agricultural products, but Meloidogyne spp. (root-knot nematode) infestations result in serious crop losses. In tomato, resistance to root-knot nematodes is controlled by the gene Mi-1, but heat stress interferes with Mi-1-associated resistance. Inconsistent results in published field and greenhouse experiments led us to test the effect of short-term midday heat stress on tomato susceptibility to Meloidogyne incognita race 1. Under controlled day/night temperatures of 25°C/21°C, ‘Amelia’, which was verified as possessing the Mi-1 gene, was deemed resistant (4.1 ± 0.4 galls/plant) and Rutgers, which does not possess the Mi-1 gene, was susceptible (132 ± 9.9 galls/plant) to M. incognita infection. Exposure to a single 3 hr heat spike of 35°C was sufficient to increase the susceptibility of ‘Amelia’ but did not affect Rutgers. Despite this change in resistance, Mi-1 gene expression was not affected by heat treatment, or nematode infection. The heat-induced breakdown of Mi-1 resistance in ‘Amelia’ did recover with time regardless of additional heat exposures and M. incognita infection. These findings would aid in the development of management strategies to protect the tomato crop at times of heightened M. incognita susceptibility.     

Influence of brown stink bug feeding,planting date and sampling time on common smut infection of maize

Phytopathogen infections are frequently influenced by both biotic and abiotic factors in a crop field. The effect of brown stink bug, Euschistus servus （Hemiptera： Pentatomidae）, feeding and planting date and sampling time on common smut （Ustilago maydis） infection percentage of maize plants was examined in 2005 and 2006, and 2010 and 2011, respectively. Brown stink bug adult feeding on maize hybrid ＂DKC6971＂ at flowering in 2005 and 2006 did not influence smut infection percentage when examined using 3 treatments （i.e., 0 adult, 5 adults, and 5 adults mixed with the smut spores）. The smut infection percentages were 〈 3% （n =12） in the 3 treatments. The smut infection percentage among the 4 weekly samplings was the same, so was natural aflatoxin contamination at harvest among the treatments. The 2nd experiment showed that planting date did not affect the smut infection percentage in either 2010 or 2011. But, the smut infection percentage from the postflowering sampling was greater than preflowering sampling in both years. The smut infection percentage varied among the germplasm lines in 2010, but not in 2011. This study demonstrated that brown stink bug feeding at flowering had no effect on smut infection in maize, and the best time for smut evaluation would be after flowering. The temperature and precipitation might have also influenced the percentage of smut-infected maize plants during the 4 years when the experiments were conducted. The similarity between kernel-colonizing U. maydis and Aspergillus flavus infections and genotype × environment interaction were also discussed.     

Patchy distribution of flexible genetic elements in bacterial populations mediates robustness to environmental uncertainty

The generation and maintenance of genetic variation seems to be a general ecological strategy of bacterial populations. Thereby they gain robustness to irregular environmental change, which is primarily the result of the dynamic evolution of biotic interactions. A benefit of maintaining population heterogeneity is that only a fraction of the population has to bear the cost of not (yet) beneficial deviation. On evolutionary time frames, an added value of the underlying mechanisms is evolvability, i.e. the heritable ability of an evolutionary lineage to generate and maintain genetic variants that are potentially adaptive in the course of evolution. Horizontal gene transfer is an important mechanism that can lead to differences between individuals within bacterial populations. Broad host-range plasmids foster this heterogeneity because they are typically present in only a fraction of the population and provide individual cells with genetic modules newly acquired from other populations or species. We postulate that the benefit of robustness on population level could balance the cost of transfer and replication functions that plasmids impose on their hosts. Consequently, mechanisms that make a subpopulation conducive to specific conjugative plasmids may have evolved, which could explain the persistence of even cryptic plasmids that do not encode any traits.     

Adverse effects of pneumoperitoneum on renal function: involvement of the endothelin and nitric oxide systems

Increased intra-abdominal pressure (IAP) during laparoscopy adversely affects kidney function. The mechanism underlying this phenomenon is largely unknown. This study was designed to investigate the involvement of endothelin (ET)-1 and nitric oxide (NO) systems in IAP-induced renal dysfunction. Rats were subjected to IAP of 14 mmHg for 1 h, followed by a deflation for 60 min (recovery). Four additional groups were pretreated with 1) ABT-627, an ET(A) antagonist; 2) A-192621, an ET(B) antagonist; 3) nitroglycerine; and 4) N(G)-nitro-L-arginine methyl ester, a NO synthase inhibitor, before IAP. Urine flow rate (V), absolute Na+ excretion (U(Na)V), glomerular filtration rate (GFR), and renal plasma flow (RPF) were determined. Significant reductions in kidney function and hemodynamics were observed when IAP was applied. V decreased from 8.1 +/- 1.0 to 5.8 +/- 0.5 microl/min, U(Na)V from 1.08 +/- 0.31 to 0.43 +/- 0.10 microeq/min, GFR from 1.84 +/- 0.12 to 1.05 +/- 0.06 ml/min (-46.9 +/- 2.7% from baseline), and RPF from 8.62 +/- 0.87 to 3.82 +/- 0.16 ml/min (-54 +/- 3.5% from baseline). When the animals were pretreated with either ABT-627 or A-192621, given alone or combined, the adverse effects of IAP on GFR, RPF, V, and U(Na)V were significantly augmented. When the animals were pretreated with nitroglycerine, the adverse effects of pneumoperitoneum on GFR and RPF were substantially improved. In contrast, pretreatment with N(G)-nitro-L-arginine methyl ester remarkably aggravated pneumoperitoneum-induced renal dysfunction. In conclusion, decreased renal excretory function and hypofiltration are induced by increased IAP. These effects are related to impairment of renal hemodynamics and could be partially ameliorated by pretreatment with nitroglycerine and aggravated by NO and ET blockade.     

Double gene deletion reveals lack of cooperation between claudin 11 and claudin 14 tight junction proteins

Members of the claudin family of proteins are the main components of tight junctions (TJs), the major selective barrier of the paracellular pathway between epithelial cells. The selectivity and specificity of TJ strands are determined by the type of claudins present. An understanding of the cooperation between different claudins in various tissues is thus important. To study the possible cooperation between claudin 11 and claudin 14, we have generated claudin 11/claudin 14 double-deficient mice, which exhibit a combination of the phenotypes found in each of the singly deficient mutants, including deafness, neurological deficits, and male sterility. These two claudins have distinct and partially overlapping expression patterns in the kidney. Claudin 11 is located in both the proximal and distal convoluted tubules, whereas claudin 14 occurs in both the thin descending and thick ascending limbs of the loop of Henle and in the proximal convoluted tubules. Although daily urinary excretion of Mg(++), and to a lesser extent of Ca(++), tends to be higher in claudin 11/claudin 14 double mutants, these changes do not reach statistical significance compared with wild-type animals. Thus, under normal conditions, co-deletion of claudin 11 and claudin 14 does not affect kidney function or ion balance. Our data demonstrate that, despite the importance of each of these claudins, there is probably no functional cooperation between them. Generation of additional mouse models in which different claudins are abolished should provide further insight into the complex interactions between claudin proteins in various physiological systems.     

Water loss and polyethylene glycol-mediated acclimatization of in vitro-grown seedlings of 5 cultivars of date palm (Phoenix dactylifera L.) plantlets

Plantlets derived from shoot-tips of seedlings from five cultivars of date palm, Phoenix dactylifera L., were subjected to polyethylene glycol in liquid medium. Comparisons of water loss of detached leaves among in vitro-grown, polyethylene glycol-treated and greenhouse-grown plants showed significant differences with treatment for all cultivars studied. For each treatment, significant differences were also found among cultivars. The common result was that the percent of moisture loss of non-treated in vitro-grown plantlets was almost twice that of greenhouse-grown plants. Polyethylene glycol-treated plantlets showed a water loss of approximately 27%, similar to that of greenhouse plants as compared to an average of 40% in control plants. This demonstrates the possibility of using polyethylene glycol as an osmoticum for in vitro acclimatization of plantlets prior to transfer to soil.Abbreviations EW epicuticular wax - MS Murashige and Skoog (1962) medium - NAA naphthalene acetic acid - PEG polyethylene glycol - PPFD photosynthetic photon flux density     

Evaluating the performance of a successive-approximations approach to parameter optimization in maximum-likelihood phylogeny estimation

Almost all studies that estimate phylogenies from DNA sequencedata under the maximum-likelihood (ML) criterion employ an approximateapproach. Most commonly, model parameters are estimated on someinitial phylogenetic estimate derived using a rapid method (neighbor-joiningor parsimony). Parameters are then held constant during a treesearch, and ideally, the procedure is repeated until convergenceis achieved. However, the effectiveness of this approximationhas not been formally assessed, in part because doing so requirescomputationally intensive, full-optimization analyses. Here,we report both indirect and direct evaluations of the effectivenessof successive approximations. We obtained an indirect evaluationby comparing the results of replicate runs on real data thatuse random trees to provide initial parameter estimates. Forsix real data sets taken from the literature, all replicateiterative searches converged to the same joint estimates oftopology and model parameters, suggesting that the approximationis not starting-point dependent, as long as the heuristic searchesof tree space are rigorous. We conducted a more direct assessmentusing simulations in which we compared the accuracy of phylogeniesestimated using full optimization of all model parameters oneach tree evaluated to the accuracy of trees estimated via successiveapproximations. There is no significant difference between theaccuracy of the approximation searches relative to full-optimizationsearches. Our results demonstrate that successive approximationis reliable and provide reassurance that this much faster approachis safe to use for ML estimation of topology.     

Effects of spironolactone and eprosartan on cardiac remodeling and angiotensin-converting enzyme isoforms in rats with experimental heart failure

Angiotensin-converting enzyme (ACE)-2 is a newly described enzyme with antagonistic effects to those of the classical ACE (ACE-1). Both ANG II and aldosterone play an important role in the pathophysiology of congestive heart failure (CHF) and in the adverse cardiac remodeling during its development. In this study, we examined the effects of experimental CHF induced by an aortocaval fistula (ACF) and of its treatment with ANG II and aldosterone inhibitors on the relative levels of ACE-1 and ACE-2. We also compared the effects of spironolactone, an aldosterone antagonist, and eprosartan, an ANG II receptor antagonist, on heart hypertrophy and fibrosis in rats with ACF. Spironolactone (15 mg x kg(-1) x day(-1) ip, via minipump) or eprosartan (5 mg x kg(-1) x day(-1) ip, via minipump) was administered into rats with ACF for 14 and 28 days. Specific antibodies were used to determine the protein levels of myocardial ACE-1 and ACE-2. ACF increased the cardiac levels of ACE-1 and decreased those of ACE-2. Heart-to-body weight ratio significantly increased from 0.30 +/- 0.004% in sham-operated controls to 0.50 +/- 0.018% and 0.56 +/- 0.044% (P < 0.001) in rats with ACF, 2 and 4 wk after surgery, respectively, in association with increased plasma levels of aldosterone. The area occupied by collagen increased from 2.33 +/- 0.27% to 6.85 +/- 0.65% and 8.03 +/- 0.93% (P < 0.01), 2 and 4 wk after ACF, respectively. Both spironolactone and eprosartan decreased cardiac mass and collagen content and reversed the shift in ACE isoforms. ACF alters the ratio between ACE isoforms in a manner that increases local ANG II and aldosterone levels. Early treatment with both ANG II and aldosterone antagonists is effective in reducing this effect. Thus ACE isoform shift may represent an important component of the development of cardiac remodeling in response to hemodynamic overload, and its correction may contribute to the beneficial therapeutic effects of renin-angiotensin-aldosterone system inhibitors.