Full establishment of arbuscular mycorrhizal symbiosis in rice occurs independently of enzymatic jasmonate biosynthesis.

Development of the mutualistic arbuscular mycorrhiza (AM) symbiosis between most land plants and fungi of the Glomeromycota is regulated by phytohormones. The role of jasmonate (JA) in AM colonization has been investigated in the dicotyledons Medicago truncatula, tomato and Nicotiana attenuata and contradicting results have been obtained with respect to a neutral, promotive or inhibitory effect of JA on AM colonization. Furthermore, it is currently unknown whether JA plays a role in AM colonization of monocotyledonous roots. Therefore we examined whether JA biosynthesis is required for AM colonization of the monocot rice. To this end we employed the rice mutant constitutive photomorphogenesis 2 (cpm2), which is deficient in JA biosynthesis. Through a time course experiment the amount and morphology of fungal colonization did not differ between wild-type and cpm2 roots. Furthermore, no significant difference in the expression of AM marker genes was detected between wild type and cpm2. However, treatment of wild-type roots with 50 μM JA lead to a decrease of AM colonization and this was correlated with induction of the defense gene PR4. These results indicate that JA is not required for AM colonization of rice but high levels of JA in the roots suppress AM development likely through the induction of defense.CG was supported by a PhD fellowship of the German National Merit Foundation (Studienstiftung des Deutschen Volkes); http://www.studienstiftung.de/ and the Roche Foundation (Switzerland). Research in the UP laboratory was supported by the SNF 'professeur boursier' grants PP00A-110874 and PP00P3-130704; http://www.snf.ch/en/Pages/default.aspx. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.This is the final version of the article. It first appeared from PLOS via http://dx.doi.org/ 10.1371/journal.pone.012342

Exoplanet Biosignatures: Observational Prospects

Exoplanet hunting efforts have revealed the prevalence of exotic worlds with diverse properties, including Earth-sized bodies, which has fueled our endeavor to search for life beyond the Solar System. Accumulating experiences in astrophysical, chemical, and climatological characterization of uninhabitable planets are paving the way to characterization of potentially habitable planets. In this paper, we review our possibilities and limitations in characterizing temperate terrestrial planets with future observational capabilities through 2030s and beyond, as a basis of a broad range of discussions on how to advance "astrobiology" with exoplanets. We discuss the observability of not only the proposed biosignature candidates themselves, but also of more general planetary properties that provide circumstantial evidence, since the evaluation of any biosignature candidate relies on their context. Characterization of temperate Earth-size planets in the coming years will focus on those around nearby late-type stars. JWST and later 30 meter-class ground-based telescopes will empower their chemical investigations. Spectroscopic studies of potentially habitable planets around solar-type stars will likely require a designated spacecraft mission for direct imaging, leveraging technologies that are already being developed and tested as part of the WFIRST mission. Successful initial characterization of a few nearby targets will be an important touchstone toward a more detailed scrutiny and a larger survey that are envisioned beyond 2030. The broad outlook this paper presents may help develop new observational techniques to detect relevant features as well as frameworks to diagnose planets based on the observables.Comment: part of a series of 5 review manuscripts of the NExSS Exoplanet Biosgnatures Worksho

Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its Environment

Here we review how environmental context can be used to interpret whether O2 is a biosignature in extrasolar planetary observations. This paper builds on the overview of current biosignature research discussed in Schwieterman et al. (2017), and provides an in-depth, interdisciplinary example of biosignature identification and observation that serves as a basis for the development of the general framework for biosignature assessment described in Catling et al., (2017). O2 is a potentially strong biosignature that was originally thought to be an unambiguous indicator for life at high-abundance. We describe the coevolution of life with the early Earth's environment, and how the interplay of sources and sinks in the planetary environment may have resulted in suppression of O2 release into the atmosphere for several billion years, a false negative for biologically generated O2. False positives may also be possible, with recent research showing potential mechanisms in exoplanet environments that may generate relatively high abundances of atmospheric O2 without a biosphere being present. These studies suggest that planetary characteristics that may enhance false negatives should be considered when selecting targets for biosignature searches. Similarly our ability to interpret O2 observed in an exoplanetary atmosphere is also crucially dependent on environmental context to rule out false positive mechanisms. We describe future photometric, spectroscopic and time-dependent observations of O2 and the planetary environment that could increase our confidence that any observed O2 is a biosignature, and help discriminate it from potential false positives. By observing and understanding O2 in its planetary context we can increase our confidence in the remote detection of life, and provide a model for biosignature development for other proposed biosignatures.Comment: 55 pages. The paper is the second in a series of 5 review manuscripts of the NExSS Exoplanet Biosignatures Workshop. Community commenting is solicited at https://nexss.info/groups/ebww

Life Beyond the Solar System: Remotely Detectable Biosignatures

For the first time in human history, we will soon be able to apply to the scientific method to the question "Are We Alone?" The rapid advance of exoplanet discovery, planetary systems science, and telescope technology will soon allow scientists to search for life beyond our Solar System through direct observation of extrasolar planets. This endeavor will occur alongside searches for habitable environments and signs of life within our Solar System. While these searches are thematically related and will inform each other, they will require separate observational techniques. The search for life on exoplanets holds potential through the great diversity of worlds to be explored beyond our Solar System. However, there are also unique challenges related to the relatively limited data this search will obtain on any individual world

Colonization kinetics of wild-type vs. <i>cpm2</i> mutant roots.

<p><b>A</b>) Colonization of wild type and <i>cpm2</i> roots with <i>Rhizophagus irregularis</i> at six weeks post inoculation (wpi). Fungal structures were stained by trypan blue. A non-colonized wild type root is shown on the left for comparison. A, arbuscule; EH, extraradical hypha; V, vesicle; size bars, 100 μm. <b>B</b>) Plants were inoculated with <i>Rhizophagus irregularis</i> and percent root length colonization was scored with a modified gridline intersect method after trypan blue staining. Means and standard errors from three biological replicates each consisting of a pool of two root systems are shown. Each replicate was represented by 20 root pieces of 2 cm length. As shown by letters no significant differences were found between <i>cpm2</i> and wild-type (ANOVA, posthoc Tukey; p≤0.05, n = 24). F_{7, 16}(total) = 1.257; F_{7, 16}(int. hyphae) = 1.153, F_{7, 16}(arbuscules) = 1.067, F_{7, 16}(vesicles) = 1.938.</p

Phosphate-dependent colonization of <i>cmp2</i> and WT.

<p><b>(A)</b> Percent root length colonization of <i>cpm2</i> and wild type roots with <i>Rhizophagus irregularis</i> at four (left) and six (right) weeks post inoculation (wpi) after fertilization with 25μM or 250μM phosphate. Root length colonization was determined by a modified gridline intersect method. Note the difference in scale between four and six wpi. Int hyphae, intraradical hyphae. Means and standard errors of six biological replicates are shown. Each replicate was represented by 20 root pieces of 2 cm length. Significant differences (ANOVA, posthoc Tukey; p≤0.05, n = 48) are indicated by different letter for comparisons within the same category (<i>i</i>. <i>e</i>. fungal structure). F(total)_7,36 = 44.188, F(hyphopodia)_7,36 = 21.993, F(int. hyphae)_7,36 = 24.046, F(arbuscules)_7,40 = 30.634, F(vesicles)_7,40 = 28.588. <b>B</b>) Expression of arbuscule marker genes <i>AM14</i> and <i>PT11</i> at four and six wpi in <i>cmp2</i> (light grey) and wild-type (dark grey) roots colonized by <i>Rhizophagus irregularis</i> and fertilized with either 25 μM (filled bars) or 250 μM (hashed bars) phosphate. Different letters indicate values that were significantly different (p≤0.05, n = 24) as determined by an ANOVA with posthoc test Tukey (F(<i>AM14</i>)_7,16 = 1.676; F(<i>PT11</i>)_7,16 = 21.499).</p

Influence of JA application on AM colonization.

<p>Plants were inoculated with <i>Rhizophagus irregularis</i> and watered twice weekly with 10 ml of jasmonic acid (JA) solution of the indicated concentrations. AM colonization and gene expression were recorded at six wpi. <b>A</b>) Influence of 5 and 50 μM JA application to the roots on colonization of wild-type plants. Means and standard errors for three replicate plants are shown. Different letters indicate significantly different values (p≤0.05, n = 9) for comparisons within the same category (<i>i</i>. <i>e</i>. fungal structure) as determined by an ANOVA with posthoc test Tukey. F(total)_2,6 = 15.87; F(hyphopodia)_2,6 = 1.0; F(int. hyphae)_2,6 = 14.878; F(arbuscules)_2,6 = 13.682; F(vesicles)_2,6 = 2.857. Int. hyphae, intraradical hyphae. <b>B</b>) Real time RT-PCR based expression in mycorrhizal roots of the AM marker gene <i>PT11</i>, the JA response gene <i>Allene Oxide Synthase 1</i> (<i>AOS1</i>) and the defense marker gene <i>Pathogenesis Related Protein 4</i> (<i>PR4</i>) in response to application of 50 μM JA. Gene expression values were normalized to the expression of the constitutive gene <i>CYCLOPHILIN2</i> and represent means of three biological replicates with standard errors. Different letters indicate significant differences for the same gene between treatments as determined by an ANOVA, posthoc Tukey (F(<i>AOS1</i>)_1,4 = 28.764; F(<i>PT11</i>)_1,4 = 18.088; F(<i>PR4</i>)_1,4 = 8.282).</p

El Diario de Pontevedra : periódico liberal: Ano XXIV Número 7067 - 1907 novembro 8

Quantification of total fatty acids in complemented A. thaliana lines. GC measurements of seeds and seedlings for Fig. 8c are shown. (XLSX 127 kb

NKG2D ligand expression in AML increases in response to HDAC inhibitor valproic acid and contributes to allorecognition by NK-cell lines with single KIR-HLA class I specificities

This study exploited alloreactivity of natural killer (NK) cells for augmenting the recognition of human acute myeloid leukemia (AML). To circumvent the inhibitory effect of killer immunoglobulin receptor (KIR) signaling, we generated NK-cell lines with single KIR specificities for major human leukocyte antigen (HLA) class I allotypes. We demonstrated efficient cytolysis of KIR-HLA class I-mismatched primary AML blasts even at low effector-to-target ratios. To define the impact of tumor-associated activating NKG2D-ligands (NKG2D-L), 66 AML patients at diagnosis were analyzed. NKG2D-L were selectively expressed on monoblastic cells in AML M4 and M5 yet absent or weakly expressed on myeloblastic cells in all AML subtypes. Paucity of cell-surface NKG2D-L was not the result of shedding because levels of soluble ULBP1 ligand measured in AML plasma were in the normal range. Notably, purified NKG2D-L(+) monoblastic cells were more susceptible to NK-mediated killing than NKG2D-L(-) myeloblastic cells. Accordingly, induction of cell-surface NKG2D-L by treatment with the histone deacetylase inhibitor, valproic acid, rendered cells more sensitive to NK cytolysis. These data suggest that adoptive transfer of selected populations of alloreactive HLA class I-mismatched NK cells in combination with pharmacologic induction of NKG2D-L merits clinical evaluation as novel approaches to immunotherapy of human AML