Quantitative trait loci affecting delta13C and response to differential water availibility in Arabidopsis thaliana

Phenotypic plasticity is an important response mechanism of plants to environmental heterogeneity. Here, we explored the genetic basis of plastic responses of Arabidopsis thaliana to water deficit by experimentally mapping quantitative trait loci (QTL) in two recombinant inbred populations (Cvi x Ler and Ler x Col). We detected genetic variation and significant genotype-by-environment interactions for many traits related to water use. We also mapped 26 QTL, including six for carbon isotope composition (delta13C). Negative genetic correlations between fruit length and fruit production as well as between flowering time and branch production were corroborated by QTL colocalization, suggesting these correlations are due to pleiotropy or physical linkage. Water-limited plants were more apically dominant with greater root:shoot ratios and higher delta13C (higher water-use efficiency) when compared to well-watered plants. Many of the QTL effects for these traits interacted significantly with the irrigation treatment, suggesting that the observed phenotypic plasticity is genetically based. We specifically searched for epistatic (QTL-QTL) interactions using a two-dimensional genome scan, which allowed us to detect epistasis regardless of additive genetic effects. We found several significant QTL-QTL interactions including three that exhibited environmental dependence. These results provide preliminary evidence for proposed genetic mechanisms underlying phenotypic plasticity.     

Autoantibodies specific for apoptotic U1-70K are superior serological markers for mixed connective tissue disease

Modifications occurring on autoantigens during cell death have been proposed to have a role in the initiation of autoimmune diseases. Patients suffering from mixed connective tissue disease (MCTD) produce autoantibodies directed to U1 small nuclear ribonucleoprotein (snRNP), and antibodies against a 70 kDa protein component, the U1-70K (70K) protein, are the most prominent. During apoptosis, 70K is cleaved by caspase-3 to a 40 kDa product, which remains associated with the complex. Autoantibodies preferentially recognizing the apoptotic form of 70K have been described previously, and an apoptosis-specific epitope on 70K has been identified. This study shows that 29 of 53 (54%) MCTD sera preferentially recognize the apoptotic form of 70K over intact 70K. Moreover, we show that antibodies directed to an apoptosis-specific epitope on 70K are more specifically associated with MCTD than other anti-70K antibodies, suggesting that apoptotic 70K is a better antigen for the detection of these antibodies in MCTD patients. Longitudinal analysis of 12 MCTD patients showed in several patients that early sera are relatively enriched with antibodies recognizing an apoptosis-specific epitope, and that the levels of these apoptosis-specific antibodies decrease in time. These findings indicate that the early detection of apoptotic 70K is of considerable interest for anti-U1 snRNP-positive patients.     

Storage and oxidation of long-chain fatty acids in the C57/BL6 mouse heart as measured by NMR spectroscopy

Triglyceride turnover in the isolated C57/BL6 mouse heart was measured by dynamic 13C edit-(1)H observe NMR and the rate of fatty acid oxidation was determined by 13C NMR isotopomer analysis. In the presence of a physiological mixture of substrates, energy was produced in the citric acid cycle by oxidation of long-chain fatty acids (18%), ketones (34%), lactate (24%), pyruvate (7%), and other sources (17%). Exogenous fatty acids appeared in the triglyceride pool at 0.24 micromol/g dry wt/min, similar to the rate of oxidation of long-chain fatty acids, 0.16 micromol/g dry wt/min. Isoproterenol decreased the rate of de novo triglyceride synthesis and increased the rate of fatty acid oxidation.     

Neural signatures of economic preferences for risk and ambiguity

People often prefer the known over the unknown, sometimes sacrificing potential rewards for the sake of surety. Overcoming impulsive preferences for certainty in order to exploit uncertain but potentially lucrative options may require specialized neural mechanisms. Here, we demonstrate by functional magnetic resonance imaging (fMRI) that individuals' preferences for risk (uncertainty with known probabilities) and ambiguity (uncertainty with unknown probabilities) predict brain activation associated with decision making. Activation within the lateral prefrontal cortex was predicted by ambiguity preference and was also negatively correlated with an independent clinical measure of behavioral impulsiveness, suggesting that this region implements contextual analysis and inhibits impulsive responses. In contrast, activation of the posterior parietal cortex was predicted by risk preference. Together, this novel double dissociation indicates that decision making under ambiguity does not represent a special, more complex case of risky decision making; instead, these two forms of uncertainty are supported by distinct mechanisms.     

Enhanced charge-independent mitochondrial free Ca(2+) and attenuated ADP-induced NADH oxidation by isoflurane: Implications for cardioprotection

Modulation of mitochondrial free Ca(2+) ([Ca(2+)](m)) is implicated as one of the possible upstream factors that initiates anesthetic-mediated cardioprotection against ischemia-reperfusion (IR) injury. To unravel possible mechanisms by which volatile anesthetics modulate [Ca(2+)](m) and mitochondrial bioenergetics, with implications for cardioprotection, experiments were conducted to spectrofluorometrically measure concentration-dependent effects of isoflurane (0.5, 1, 1.5, 2mM) on the magnitudes and time-courses of [Ca(2+)](m) and mitochondrial redox state (NADH), membrane potential (ΔΨ(m)), respiration, and matrix volume. Isolated mitochondria from rat hearts were energized with 10mM Na(+)- or K(+)-pyruvate/malate (NaPM or KPM) or Na(+)-succinate (NaSuc) followed by additions of isoflurane, 0.5mM CaCl(2) (≈200nM free Ca(2+) with 1mM EGTA buffer), and 250μM ADP. Isoflurane stepwise: (a) increased [Ca(2+)](m) in state 2 with NaPM, but not with KPM substrate, despite an isoflurane-induced slight fall in ΔΨ(m) and a mild matrix expansion, and (b) decreased NADH oxidation, respiration, ΔΨ(m), and matrix volume in state 3, while prolonging the duration of state 3 NADH oxidation, respiration, ΔΨ(m), and matrix contraction with PM substrates. These findings suggest that isoflurane's effects are mediated in part at the mitochondrial level: (1) to enhance the net rate of state 2 Ca(2+) uptake by inhibiting the Na(+)/Ca(2+) exchanger (NCE), independent of changes in ΔΨ(m) and matrix volume, and (2) to decrease the rates of state 3 electron transfer and ADP phosphorylation by inhibiting complex I. These direct effects of isoflurane to increase [Ca(2+)](m), while depressing NCE activity and oxidative phosphorylation, could underlie the mechanisms by which isoflurane provides cardioprotection against IR injury at the mitochondrial level.     

Genome editing in fruit,ornamental, and industrial crops

Transgenic Research - The advent of genome editing has opened new avenues for targeted trait enhancement in fruit, ornamental, industrial, and all specialty crops. In particular, CRISPR-based...     

Reduced mitochondrial Ca2+ loading and improved functional recovery after ischemia-reperfusion injury in old vs. young guinea pig hearts

Oxidative damage and impaired cytosolic Ca(2+) concentration ([Ca(2+)](cyto)) handling are associated with mitochondrial [Ca(2+)] ([Ca(2+)](mito)) overload and depressed functional recovery after cardiac ischemia-reperfusion (I/R) injury. We hypothesized that hearts from old guinea pigs would demonstrate impaired [Ca(2+)](mito) handling, poor functional recovery, and a more oxidized state after I/R injury compared with hearts from young guinea pigs. Hearts from young (～4 wk) and old (>52 wk) guinea pigs were isolated and perfused with Krebs-Ringer solution (2.1 mM Ca(2+) concentration at 37°C). Left ventricular pressure (LVP, mmHg) was measured with a balloon, and NADH, [Ca(2+)](mito) (nM), and [Ca(2+)](cyto) (nM) were measured by fluorescence with a fiber optic probe placed against the left ventricular free wall. After baseline (BL) measurements, hearts were subjected to 30 min global ischemia and 120 min reperfusion (REP). In old vs. young hearts we found: 1) percent infarct size was lower (27 ± 9 vs. 57 ± 2); 2) developed LVP (systolic-diastolic) was higher at 10 min (57 ± 11 vs. 29 ± 2) and 60 min (55 ± 10 vs. 32 ± 2) REP; 3) diastolic LVP was lower at 10 and 60 min REP (6 ± 3 vs. 29 ± 4 and 3 ± 3 vs. 21 ± 4 mmHg); 4) mean [Ca(2+)](cyto) was higher during ischemia (837 ± 39 vs. 541 ± 39), but [Ca(2+)](mito) was lower (545 ± 62 vs. 975 ± 38); 5) [Ca(2+)](mito) was lower at 10 and 60 min REP (129 ± 2 vs. 293 ± 23 and 122 ± 2 vs. 234 ± 15); 6) reduced inotropic responses to dopamine and digoxin; and 7) NADH was elevated during ischemia in both groups and lower than BL during REP. Contrary to our stated hypotheses, old hearts showed reduced [Ca(2+)](mito), decreased infarction, and improved basal mechanical function after I/R injury compared with young hearts; no differences were noted in redox state due to age. In this model, aging-associated protection may be linked to limited [Ca(2+)](mito) loading after I/R injury despite higher [Ca(2+)](cyto) load during ischemia in old vs. young hearts.