Summary
Abietane diterpenoids are major constituents of conifer resins that have important industrial and medicinal applications. However, their function in plants is poorly understood. Here we show ...that dehydroabietinal (DA), an abietane diterpenoid, is an activator of systemic acquired resistance (SAR), which is an inducible defense mechanism that is activated in the distal, non‐colonized, organs of a plant that has experienced a local foliar infection. DA was purified as a SAR‐activating factor from vascular sap of Arabidopsis thaliana leaves treated with a SAR‐inducing microbe. Locally applied DA is translocated through the plant and systemically induces the accumulation of salicylic acid (SA), an important activator of defense, thus leading to enhanced resistance against subsequent infections. The NPR1 (NON‐EXPRESSOR OF PR GENES1), FMO1 (FLAVIN‐DEPENDENT MONOOXYGENASE1) and DIR1 (DEFECTIVE IN INDUCED RESISTANCE1) genes, which are critical for biologically induced SAR, are also required for the DA‐induced SAR, which is further enhanced by azelaic acid, a defense priming molecule. In response to the biological induction of SAR, DA in vascular sap is redistributed into a SAR‐inducing ‘signaling DA’ pool that is associated with a trypsin‐sensitive high molecular weight fraction, a finding that suggests that DA‐orchestrated SAR involves a vascular sap protein(s).
A reduction in the lignin content in transgenic plants induces the ectopic expression of defense genes, but the importance of altered lignin composition in such phenomena remains unclear.
Two ...Arabidopsis lines with similar lignin contents, but strikingly different lignin compositions, exhibited different quantitative and qualitative transcriptional responses. Plants with lignin composed primarily of guaiacyl units overexpressed genes responsive to oomycete and bacterial pathogen attack, whereas plants with lignin composed primarily of syringyl units expressed a far greater number of defense genes, including some associated with cis-jasmone-mediated responses to aphids; these plants exhibited altered responsiveness to bacterial and aphid inoculation.
Several of the defense genes were differentially induced by water-soluble extracts from cell walls of plants of the two lines. Glycome profiling, fractionation and enzymatic digestion studies indicated that the different lignin compositions led to differential extractability of a range of heterogeneous oligosaccharide epitopes, with elicitor activity originating from different cell wall polymers.
Alteration of lignin composition affects interactions with plant cell wall matrix polysaccharides to alter the sequestration of multiple latent defense signal molecules with an impact on biotic stress responses.
Fusarium head blight (FHB) is a destructive disease of cereal crops such as wheat and barley. Previously, expression in wheat of the Arabidopsis NPR1 gene (AtNPR1), which encodes a key regulator of ...salicylic acid (SA) signaling, was shown to reduce severity of FHB caused by Fusarium graminearum. It was hypothesized that SA signaling contributes to wheat defense against F. graminearum. Here, we show that increased accumulation of SA in fungus-infected spikes correlated with elevated expression of the SA-inducible pathogenesis-related 1 (PR1) gene and FHB resistance. In addition, FHB severity and mycotoxin accumulation were curtailed in wheat plants treated with SA and in AtNPR1 wheat, which is hyper-responsive to SA. In support of a critical role for SA in basal resistance to FHB, disease severity was higher in wheat expressing the NahG-encoded salicylate hydroxylase, which metabolizes SA. The FHB-promoting effect of NahG was overcome by application of benzo (1,2,3), thiadiazole-7 carbothioic acid S-methyl ester, a synthetic functional analog of SA, thus confirming an important role for SA signaling in basal resistance to FHB. We further demonstrate that jasmonate signaling has a dichotomous role in wheat interaction with F. graminearum, constraining activation of SA signaling during early stages of infection and promoting resistance during the later stages of infection.
Efficient communication between the pest-colonised and non-colonised organs is vital for the timely manifestation of defences that restrict systemic spread of pests. The vasculature provides an ...important conduit for translocation of signals that contribute to long-distance communication within a plant. Airborne signals also contribute to this process. In recent years, major advances have been made in identifying metabolites that are candidate systemic signals in plant defence against pathogens. Methyl salicylate, jasmonates, azelaic acid and a diterpenoid have been implicated as mobile signals associated with the activation of systemic acquired resistance (SAR), which confers enhanced resistance against a broad spectrum of pathogens. By contrast, auxins probably contribute to negative regulation of systemic defences.
A direct‐infusion electrospray ionization triple–quadrupole mass spectrometry method with multiple reaction monitoring (MRM) was employed to measure 264 lipid analytes extracted from leaves of ...Arabidopsis thaliana subjected to mechanical wounding. The method provided precise measurements with an average coefficient of variation of 6.1%. Lipid classes analyzed comprised galactolipids and phospholipids (including monoacyl molecular species, molecular species with oxidized acyl chains, phosphatidic acids (PAs)), tri‐ and tetra‐galactosyldiacylglycerols (TrGDGs and TeGDGs), head‐group‐acylated galactolipids, and head‐group‐acylated phosphatidylglycerol (acPG), sulfoquinovosyldiacylglycerols (SQDGs), sphingolipids, di‐ and tri‐acylglycerols (DAGs and TAGs), and sterol derivatives. Of the 264 lipid analytes, 254 changed significantly in response to wounding. In general, levels of structural lipids decreased, whereas monoacyl molecular species, galactolipids and phosphatidylglycerols (PGs) with oxidized fatty acyl chains, PAs, TrGDGs, TeGDGs, TAGs, head‐group‐acylated galactolipids, acPG, and some sterol derivatives increased, many transiently. The observed changes are consistent with activation of lipid oxidizing, hydrolyzing, glycosylating, and acylating activities in the wounding response. Correlation analysis of the levels of lipid analytes across individual control and treated plants was used to construct a lipid dendrogram and to define clusters and sub‐clusters of lipid analytes, each composed of a group of lipids which occurred in a coordinated manner. Current knowledge of metabolism supports the notion that observed sub‐clusters comprise lipids generated by a common enzyme and/or metabolically downstream of a common enzyme. This work demonstrates that co‐occurrence analysis, based on correlation of lipid levels among plants, is a powerful approach to defining lipids generated in vivo by a common enzymatic pathway.
We developed a procedure for the preparation of whole transcriptome cDNA libraries depleted of ribosomal RNA from only 1 μg of total RNA. The method relies on a collection of short, computationally ...selected oligonucleotides, called 'not-so-random' (NSR) primers, to obtain full-length, strand-specific representation of nonribosomal RNA transcripts. In this study we validated the technique by profiling human whole brain and universal human reference RNA using ultra-high-throughput sequencing.
► Single phase Ni0.5Cu0.25Zn0.25Fe2−xInxO4 ferrites were synthesized by citrate–nitrate precursor auto combustion. ► Magnetic properties decreased due to the substitution of In3+ ions. ► Dielectric ...properties decreased with increase in frequency. ► This composition can be used for multilayer chip inductor (MLCI) applications.
In submitted research; nanocrystalline powders having elements Ni0.5Cu0.25Zn0.25Fe2−xInxO4 with varied amounts of indium (x=0.0, 0.1, 0.2, 0.3 and 0.4) were grown-up by modified citrate to nitrate alchemy. The realism of single phase cubic spinel creation of the synthesized ferrite samples was studied by the DTA-TGA, XRD, SEM, EDX, FT-IR, VSM and dielectric measurements. SEM was applied to inspect the morphological variations and EDX was used to determine the compositional mass ratios. The studies on the dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ), ac conductivity (σac), resistive and reactive parts of the impedance analysis (Z’ and Z”) at room temperature were also carried out. The saturation magnetizations (Ms) were determined using the vibrating sample magnetometer (VSM). Ms. decreased with the increase In3+ doping content, as Fe3+ of 5μB ions are replaced by In3+ of 0μB ions.
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