Defense response of a pepper cultivar cv. Sy-2 is induced at temperatures below 24°C

Temperature is one of the most important environmental factors that influence plant growth and development. Recent studies imply that plants show various responses to non-extreme ambient temperatures. Previously, we have found that a pepper cultivar cv. Sy-2 (Capsicum chinense) shows developmental defects at temperatures below 24°C. In this study, to gain new insights into the temperature sensitivity of cv. Sy-2, temperature-sensitive genes were screened using microarray techniques. At restrictive temperature of 20°C, almost one-fourth of the 411 up-regulated genes were defense related or predicted to be defense related. Further expression analyses of several defense-related genes showed that defense-related genes in cv. Sy-2 were constitutively expressed at temperatures below 24°C. Moreover, accumulation of high level of salicylic acid (SA) in cv. Sy-2 grown at 20°C suggests that the defense response is activated in the absence of pathogens. To confirm that the defense response is induced in cv. Sy-2 below 24°C, we evaluated the resistance to biotrophic bacterial pathogen Xanthomonas campestris pv. vesicatoria and necrotrophic fungal pathogen Cercospora capsici. Cv. Sy-2 showed enhanced resistance to X. campestris pv. vesicatoria, but not to C. capsici.     

Differential encoding of factors influencing predicted reward value in monkey rostral anterior cingulate cortex

Background

The value of a predicted reward can be estimated based on the conjunction of both the intrinsic reward value and the length of time to obtain it. The question we addressed is how the two aspects, reward size and proximity to reward, influence the responses of neurons in rostral anterior cingulate cortex (rACC), a brain region thought to play an important role in reward processing.

Methods and Findings

We recorded from single neurons while two monkeys performed a multi-trial reward schedule task. The monkeys performed 1–4 sequential color discrimination trials to obtain a reward of 1–3 liquid drops. There were two task conditions, a valid cue condition, where the number of trials and reward amount were associated with visual cues, and a random cue condition, where the cue was picked from the cue set at random. In the valid cue condition, the neuronal firing is strongly modulated by the predicted reward proximity during the trials. Information about the predicted reward amount is almost absent at those times. In substantial subpopulations, the neuronal responses decreased or increased gradually through schedule progress to the predicted outcome. These two gradually modulating signals could be used to calculate the effect of time on the perception of reward value. In the random cue condition, little information about the reward proximity or reward amount is encoded during the course of the trial before reward delivery, but when the reward is actually delivered the responses reflect both the reward proximity and reward amount.

Conclusions

Our results suggest that the rACC neurons encode information about reward proximity and amount in a manner that is dependent on utility of reward information. The manner in which the information is represented could be used in the moment-to-moment calculation of the effect of time and amount on predicted outcome value.     

Thermal luminescence spectra of polyamides and their Maillard reaction with reducing sugars

Thermal luminescence (TL) spectra of polyamides were measured with a Fourier‐transform chemiluminescence spectrometer to elucidate the emission mechanism. A TL band of ε‐polylysine with a peak at 542 nm observed at 403 K was assigned to the emission due to the interaction of the –CO–NH– group with oxygen molecules by comparison with nylon‐6, polyglycine, and polyalanine. When the sample was kept at 453 K, the intensity of the TL band decreased and the wavelength of the peak shifted to 602 nm, which was assigned to the emission due to the interaction of the NH₂ group on the side chain with oxygen molecules by comparison with monomeric lysine. A weak emission with a peak at 668 nm was assigned to the advanced glycosylation end products (AGEs) yielded by the Maillard reaction with a catalytic amount of water. To understand this reaction and to examine the TL emission of AGEs, we measured TL spectra of mixtures of polylysine and reducing sugars such as glucose, maltose, lactose, and dextrin. The minimum temperature for TL emission, wavelength of the peak and the relative intensities of the TL emission were found to depend on the size of the sugars. Copyright © 2011 John Wiley & Sons, Ltd.     

Fungal endophytes of grasses

Epichloae endophytes form mutualistic symbiotic associations with temperate grasses and confer on the host a number of bioprotective benefits through production of fungal secondary metabolites and changed host metabolism. Maintenance of this mutualistic interaction requires that growth of the endophyte within the host is restricted. Recent work has shown that epichloae endophytes grow in the leaves by intercalary division and extension rather than tip growth. This novel pattern of growth enables the fungus to synchronise its growth with that of the host. Reactive oxygen species signalling is required to maintain this pattern of growth. Disruption of components of the NADPH oxidase complex or a MAP kinase, result in a switch from restricted to proliferative growth and a breakdown in the symbiosis. RNAseq analysis of mutant and wild-type associations identifies key fungal and plant genes that define the symbiotic state. Endophyte genes for secondary metabolite biosynthesis are only expressed in the plant and under conditions of restricted growth.     

Colorimetric cell proliferation assay for microorganisms in microtiter plate using water-soluble tetrazolium salts

A colorimetric method to assay cell proliferation of microorganisms in 96-well microtiter plates using water-soluble tetrazolium salts and electron mediators was developed. Combinations of 6 kinds of water-soluble tetrazolium salts and 27 kinds of electron mediators that considered the metabolic efficiency of microorganisms and the influence with medium components were investigated. 2-Methyl-1,4-naphthoquinone (NQ) was reduced most effectively by various species of microorganisms, and a combination of WST-8 as a water-soluble tetrazolium salt with 2-methyl-1,4-NQ repressed the increase in background due to medium components. In the presence of 2-methyl-1,4-NQ, WST-8 was reduced by microbial cells to formazan, which exhibited maximum absorbance at 460 nm. The proposed tetrazolium method could be applied to measure proliferations of various microbial cells including 3 kinds of yeast, 9 kinds of Gram-positive bacteria, and 10 kinds of Gram-negative bacteria. Linear relationships between the absorbance and viable microbial cell density were obtained in all microorganisms, suggesting that the absorbance change reflected the microbial cell proliferation.     

Specific cation effect on quenching reactions of excited tris(α,α-diimine)ruthenium(II) and tris(2,2-bipyridine)chromium(III) by tris(oxalato)- and tris(malnato)chromates(III) in aqueous solutions

Specific salt effects were studied on the quenching reaction of excited [Ru(N-N)₃]²⁺ (N-N=2,2^′-bipyridine (bpy), 1,10-phenanthrorine (phen)) and [Cr(bpy)₃]³⁺ by [Cr(ox)₃]³⁻ (ox=oxalate ion) and [Cr(mal)₃]³⁻ (mal=malonate ion) in aqueous solutions as a function of alkali metal ions which were added for adjustment of ionic strength. The value of k_q, quenching rate constants, and k₁, energy transfer rate constant in encounter complex, is changed by the cations as the order of Li⁺ > Na⁺ > K⁺ ≈ Rb⁺ ? Cs⁺, although diffusion rate constants are not changed by the co-existing cations. Among the quenching reactions investigated in this work, a ratio of k₁ values in the aqueous solutions whose ionic strength was adjusted with LiCl and KCl, k₁^LiCl/k₁^KCl, is larger for quenching systems of closely approached donor-acceptor pair than loosely bounded pair. These results indicate that co-existing alkali cation tunes the distance between donor and acceptor in encounter complex where energy transfer occurs.     

Diverse effects of ethanol on the pathway of inducible prostaglandin E2 production in macrophages.

The effects of ethanol on inducible prostaglandin production in RAW macrophages were investigated. Indomethacin (1 microM) or cycloheximide (1 microM) abolished prostaglandin E2 (PGE2) production induced by lipopolysaccharide (LPS, 1 microg/ml). Ethanol at concentrations from 100 mM to 600 mM concentration-dependently inhibited inducible PGE2 production, while ethanol only at higher concentrations (400 mM or more) showed cytotoxity to the cells. Cyclooxygenase-2 (COX-2) activity, estimated by transformation of exogenous arachidonic acid into PGE2, was not affected by ethanol (100-400 mM). LPS-induced expression of COX-2 mRNA was inhibited by ethanol (50-400 mM). On the other hand, protein expression of COX-2 by LPS was significantly increased by ethanol (100-400 mM). Ethanol alone at concentrations up to 600 mM did not induce expression of COX-2 protein. In a medium containing arachidonic acid (1 microM), ethanol at a low concentration (100 mM) did not significantly affect LPS-induced PGE2 production. These results suggest that ethanol shows diverse effects on the pathway of inducible PGE2 production in macrophages. Finally, ethanol may suppress utilization of arachidonic acid, resulting in reduction of inducible PGE2 production. Further study is needed to elucidate the mechanism of dissociation of ethanol effects on protein and mRNA expression.     

Xylan Synthase Activity in Isolated Mesophyll Cells of Zinnia elegans during Differentiation to Tracheary Elements

A paniculate fraction obtained from mesophyll cells of Zinniaelegans that were differentiating into tracheary elements exhibitedxylan synthase activity, catalyzing the transfer of ^MC-xylosefrom UDP-D-[U-¹⁴C]-xylose into 1,4-linked xylan. The activityincreased transiently at the same time as thickening of secondarycell walls occurred, a process that is accompanied by the depositionof cellulose, xylan and lignin. (Received August 3, 1990; Accepted December 6, 1990)