Stomatal density and aperture length in four plant species grown across a subambient CO2 gradient

Stomatal density, stomatal aperture length, area/leaf, and number of stomata/leaf were measured after the annual C₃ agronomic grasses oats (Avena sativa) and wheat (Triticum aestivum), the C, woody legume honey mesquite (Prosopis glandulosa), and the perennial C₄ grass little bluestem (Schizachyrium scoparium) were grown across a subambient carbon dioxide concentration ([CO₂]) gradient from near 200 to 350 μmol/mol in a growth chamber. The purpose was to determine if the size and density of stomata vary in response to atmospheric [CO₂] during growth, across a subambient [CO₂] range representative of the doubling that has occurred since the last ice age. Changes in stomatal density and aperture length with increasing [CO₂] were small when detected. Stomatal density decreased on adaxial flag leaf surfaces of wheat, and aperture length increased slightly with [CO₂], Leaf area and number of stomata/flag leaf increased by similar proportions with [CO₂] in two wheat cultivars. No consistent relationship between [CO₂] and stomatal density or size was detected in mesquite, oats, or little bluestem. We conclude that individual plants of these species lack the plasticity to significantly alter stomatal density and aperture length in response to increasing atmospheric [CO₂] in a single generation (annuals) or growing season (perennials).     

Genetic variation in DNMT3B and increased global DNA methylation is associated with suicide attempts in psychiatric patients

Recently, a significant epigenetic component in the pathology of suicide has been realized. Here we investigate candidate functional SNPs in epigenetic‐regulatory genes, DNMT1 and DNMT3B, for association with suicide attempt (SA) among patients with co‐existing psychiatric illness. In addition, global DNA methylation levels [5‐methyl cytosine (5‐mC%)] between SA and psychiatric controls were quantified using the Methylflash Methylated DNA Quantification Kit. DNA was obtained from blood of 79 suicide attempters and 80 non‐attempters, assessed for DSM‐IV Axis I disorders. Functional SNPs were selected for each gene (DNMT1; n = 7, DNMT3B; n = 10), and genotyped. A SNP (rs2424932) residing in the 3′ UTR of the DNMT3B gene was associated with SA compared with a non‐attempter control group (P = 0.001; Chi‐squared test, Bonferroni adjusted P value = 0.02). Moreover, haplotype analysis identified a DNMT3B haplotype which differed between cases and controls, however this association did not hold after Bonferroni correction (P = 0.01, Bonferroni adjusted P value = 0.56). Global methylation analysis showed that psychiatric patients with a history of SA had significantly higher levels of global DNA methylation compared with controls (P = 0.018, Student's t‐test). In conclusion, this is the first report investigating polymorphisms in DNMT genes and global DNA methylation quantification in SA risk. Preliminary findings suggest that allelic variability in DNMT3B may be relevant to the underlying diathesis for suicidal acts and our findings support the hypothesis that aberrant DNA methylation profiles may contribute to the biology of suicidal acts. Thus, analysis of global DNA hypermethylation in blood may represent a biomarker for increased SA risk in psychiatric patients.     

A flagellate protozoan from Mythimna separata (Lepidoptera: Noctuidae)

Abstract

A trypanosomatid flagellate, Herpetomonas sp., is recorded from an adult Mythimna separata (Walker) (Lepidoptera: Noctuidae). Promastigote, paramastigote, and opisthomastigote stages measured 3.4–12 × 1.3–4.3 μm, Giemsastained, with flagella measuring 13.8–18.7 μm. A few amastigotes (3.9–8.3 × 3.7–6.7 μm) were also observed. Fourteen larvae fed with a suspension of flagellates were found later to be infected with the protozoan. No flagellate infections were found in the hymenopteran parasitoid, Apanteles ruficus (Haliday), or the hyperparasitoid, Trichomalopsis sp.     

Contrasting Role of Temperature in Structuring Regional Patterns of Invasive and Native Pestilential Stink Bugs

Objectives

Assessment and identification of spatial structures in the distribution and abundance of invasive species is important for unraveling the underlying ecological processes. The invasive agricultural insect pest Halyomorpha halys that causes severe economic losses in the United States is currently expanding both within United States and across Europe. We examined the drivers of H. halys invasion by characterizing the distribution and abundance patterns of H. halys and native stink bugs (Chinavia hilaris and Euschistus servus) across eight different spatial scales. We then quantified the interactive and individual influences of temperature, and measures of resource availability and distance from source populations, and their relevant spatial scales. We used Moran’s Eigenvector Maps based on Gabriel graph framework to quantify spatial relationships among the soybean fields in mid-Atlantic Unites States surveyed for stink bugs.

Findings

Results from the multi-spatial scale, multivariate analyses showed that temperature and its interaction with resource availability and distance from source populations structures the patterns in H. halys at very broad spatial scale. H. halys abundance decreased with increasing average June temperature and distance from source population. H. halys were not recorded at fields with average June temperature higher than 23.5°C. In parts with suitable climate, high H. halys abundance was positively associated with percentage developed open area and percentage deciduous forests at 250m scale. Broad scale patterns in native stink bugs were positively associated with increasing forest cover and, in contrast to the invasive H. halys, increasing mean July temperature. Our results identify the contrasting role of temperature in structuring regional patterns in H. halys and native stink bugs, while demonstrating its interaction with resource availability and distance from source populations for structuring H. halys patterns.

Conclusion

These results help predicting the pest potential of H. halys and vulnerability of agricultural systems at various regions, given the climatic conditions, and its interaction with resource availability and distance from source populations. Monitoring and control efforts within parts of the United States and Europe with more suitable climate could focus in areas of peri-urban developments with deciduous forests and other host plants, along with efforts to reduce propagule pressure.     

High levels of cyclic‐di‐GMP in plant‐associated Pseudomonas correlate with evasion of plant immunity

The plant innate immune system employs plasma membrane‐localized receptors that specifically perceive pathogen/microbe‐associated molecular patterns (PAMPs/MAMPs). This induces a defence response called pattern‐triggered immunity (PTI) to fend off pathogen attack. Commensal bacteria are also exposed to potential immune recognition and must employ strategies to evade and/or suppress PTI to successfully colonize the plant. During plant infection, the flagellum has an ambiguous role, acting as both a virulence factor and also as a potent immunogen as a result of the recognition of its main building block, flagellin, by the plant pattern recognition receptors (PRRs), including FLAGELLIN SENSING2 (FLS2). Therefore, strict control of flagella synthesis is especially important for plant‐associated bacteria. Here, we show that cyclic‐di‐GMP [bis‐(3′‐5′)‐cyclic di‐guanosine monophosphate], a central regulator of bacterial lifestyle, is involved in the evasion of PTI. Elevated cyclic‐di‐GMP levels in the pathogen Pseudomonas syringae pv. tomato (Pto) DC3000, the opportunist P. aeruginosa PAO1 and the commensal P. protegens Pf‐5 inhibit flagellin synthesis and help the bacteria to evade FLS2‐mediated signalling in Nicotiana benthamiana and Arabidopsis thaliana. Despite this, high cellular cyclic‐di‐GMP concentrations were shown to drastically reduce the virulence of Pto DC3000 during plant infection. We propose that this is a result of reduced flagellar motility and/or additional pleiotropic effects of cyclic‐di‐GMP signalling on bacterial behaviour.     

Imprecise Spacer Acquisition Generates CRISPR-Cas Immune Diversity through Primed Adaptation

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