"Since humans first began burning fossil fuels on a large scale, the ocean has increased its acidity by 30 percent. To put that into perspective, imagine biting into an apple and discovering it’s as acidic as vinegar. Worse, says Feely, the trend has been accelerating as more and more CO2 is emitted. “If we continue on the same trajectory,” he cautions, “by the end of this century we will see a 100-to-150 percent increase in the acidity of the ocean.”"
Microorganisms use siderophores to obtain iron from the environment. In pathogenic interactions, siderophores are involved in iron acquisition from the host and are sometimes necessary for the expression of full virulence. This review summarizes the main data describing the role of these iron scavengers in animal and plant defence systems. To protect themselves against iron theft, mammalian hosts have developed a hypoferremia strategy that includes siderophore-binding molecules called siderocalins. In addition to microbial ferri-siderophore sequestration, siderocalins are involved in triggering immunity. In plants, no similar mechanisms have been described and many fewer data are available, although recent advances have shed light on the role of siderophores in plant–pathogen interactions. Siderophores can trigger immunity in plants in several contexts. The most frequently described situation involving siderophores is induced systemic resistance (ISR) triggered by plant-growth-promoting rhizobacteria. Although ISR responses have been observed after treating roots with certain siderophores, the underlying mechanisms are poorly understood. Immunity can also be triggered by siderophores in leaves. Siderophore perception in plants appears to be different from the well-known perception mechanisms of other microbial compounds, known as microbe-associated molecular patterns. Scavenging iron per se appears to be a novel mechanism of immunity activation, involving complex disturbance of metal homeostasis. Receptor-specific recognition of siderophores has been described in animals, but not in plants. The review closes with an overview of the possible mechanisms of defence activation, via iron scavenging by siderophores or specific siderophore recognition by the plant host.
You all know I love cross-kingdom "infochemicals" (aka semiochemicals - "sema" in Greek means sign and is used in the semaphore language of flags). Check out this new paper "Interaction and signalling between a cosmopolitan phytoplankton and associated bacteria". Take home message:
"A Sulfitobacter species promotes diatom cell division via secretion of the hormone indole-3-acetic acid, synthesized by the bacterium using both diatom-secreted and endogenous tryptophan. Indole-3-acetic acid and tryptophan serve as signalling molecules that are part of a complex exchange of nutrients, including diatom-excreted organosulfur molecules and bacterial-excreted ammonia."
Volatile Glycosylation in Tea Plants: Sequential Glycosylations for the Biosynthesis of Aroma β-Primeverosides Are Catalyzed by Two Camellia sinensis Glycosyltransferases "Tea, manufactured from Camellia sinensis, is the most popular beverage in the world and is classified as black, green, or oolong tea based on the manufacturing process, which affects the composition and quantity of aroma compounds. Tea plants store volatile organic compounds (VOCs; monoterpene, aromatic, and aliphatic alcohols) in the leaves in the form of water-soluble diglycosides, primarily as β-primeverosides. Here, we identified two UDP-glycosyltransferases (UGTs) from C. sinensis, UGT85K11 (CsGT1) and UGT94P1 (CsGT2), converting VOCs into β-primeverosides by sequential glucosylation and xylosylation, respectively. Our findings reveal the mechanism of aroma β-primeveroside biosynthesis in C. sinensis. This information can be used to preserve tea aroma better during the manufacturing process and to investigate the mechanism of plant chemical defenses." http://www.plantphysiol.org/content/168/2/464.abstract
Scientists receive (and offer) much advice on how to write an effective paper that their colleagues will read, cite, and celebrate [2–15]. Fundamentally, the advice is similar to that given to journalists: keep the text short, simple, bold, and easy to understand. Many resources recommend the parsimonious use of adjectives and adverbs, the use of present tense, and a consistent style. Here we put this advice to the test, and measure the impact of certain features of academic writing on success, as proxied by citations.
The abstract epitomizes the scientific writing style, and many journals force their authors to follow a formula—including a very strict word-limit, a specific organization into paragraphs, and even the articulation of particular sentences and claims (e.g., “Here we show that…”).
Data generated from next generation sequencing (NGS) will soon comprise the majority of information about arbuscular mycorrhizal fungal (AMF) communities. Although these approaches give deeper insight, analysing NGS data involves decisions that can significantly affect results and conclusions. This is particularly true for AMF community studies, because much remains to be known about their basic biology and genetics. During a workshop in 2013, representatives from seven research groups using NGS for AMF community ecology gathered to discuss common challenges and directions for future research. Our goal was to improve the quality and accessibility of NGS data for the AMF research community. Discussions spanned sampling design, sample preservation, sequencing, bioinformatics and data archiving. With concrete examples we demonstrated how different approaches can significantly alter analysis outcomes. Failure to consider the consequences of these decisions may compound bias introduced at each step along the workflow. The products of these discussions have been summarized in this paper in order to serve as a guide for any researcher undertaking NGS sequencing of AMF communities.
A limiting factor in synthetic gene circuit design is the number of independent control elements that can be combined together in a single system. Here, we present RiboTALEs, a new class of inducible repressors that combine the specificity of TALEs with the ability of riboswitches to recognize exogenous signals and differentially control protein abundance. We demonstrate the capacity of RiboTALEs, constructed through different combinations of TALE proteins and riboswitches, to rapidly and reproducibly control the expression of downstream targets with a dynamic range of 243.7 ± 17.6-fold, which is adequate for many biotechnological applications.
Plants and animals perceive diverse microbe-associated molecular patterns (MAMPs) via pattern recognition receptors and activate innate immune signalling. The actin cytoskeleton has been suggested as a target for innate immune signalling and a key transducer of cellular responses. However, the molecular mechanisms underlying actin remodelling and the precise functions of these rearrangements during innate immunity remain largely unknown. Here we demonstrate rapid actin remodelling in response to several distinct MAMP signalling pathways in plant epidermal cells. The regulation of actin dynamics is a convergence point for basal defence machinery, such as cell wall fortification and transcriptional reprogramming. Our quantitative analyses of actin dynamics and genetic studies reveal that MAMP-stimulated actin remodelling is due to the inhibition of capping protein (CP) by the signalling lipid, phosphatidic acid. In addition, CP promotes resistance against bacterial and fungal phytopathogens. These findings demonstrate that CP is a central target for the plant innate immune response.
Many plant genes belong to families that arise from extensive proliferation and diversification allowing the evolution of functionally new proteins. Here we report the characterization of a group of proteins evolved from WRKY and exocyst complex subunit Exo70 proteins through fusion with a novel transmembrane (TM) domain in soybean (Glycine max). From the soybean genome, we identified a novel WRKY-related protein (GmWRP1) that contains a WRKY domain with no binding activity for W-box sequences. GFP fusion revealed that GmWRP1 was targeted to the Golgi apparatus through its N-terminal TM domain. Similar Golgi-targeting TM domains were also identified in members of a new subfamily of Exo70J proteins involved in vesicle trafficking. The novel TM domains are structurally most similar to the endosomal cytochrome b561 from birds and close homologues of GmWRP1 and GmEx070J proteins with the novel TM domain have only been identified in legumes. Transient expression of some GmExo70J proteins or the Golgi-targeting TM domain in tobacco altered the subcellular structures labelled by a fluorescent Golgi marker. GmWRP1 transcripts were detected at high levels in roots, flowers, pods, and seeds, and the expression levels of GmWRP1 and GmExo70J genes were elevated with increased age in leaves. The legume-specific, Golgi apparatus-localized GmWRP1 and GmExo70J proteins are probably involved in Golgi-mediated vesicle trafficking of biological molecules that are uniquely important to legumes.
With the rising number of sequenced pathogen genomes, computational prediction of effector proteins holds promise as a fast and economical technique to define candidates for subsequent laboratory work. Bacterial effectors delivered to the host via dedicated pathogen-derived delivery mechanisms, such as the type III secretion system, can be predicted using machine learning approaches based on protein sequence information. In oomycetes, consensus sequence motifs implicated in host translocation, such as RXLR, can be exploited for effector prediction. However, computational effector prediction in fungi is challenging due to a lack of known protein features that are common to fungal effectors and the low number of characterized effectors for individual species, which limits the use of machine learning approaches.
OsDCL1 RNAi lines showed enhanced resistance to rice blast. •
A negative feedback loop between miR162a and OsDCL1 was identified. •
Differentially expressed miRNAs responsive to rice blast infection were identified. •
PR and PTI responsive genes were constitutively activated in OsDCL1 RNAi lines.
The RNaseIII enzyme Dicer-like 1 (DCL1) processes the microRNA biogenesis and plays a determinant role in plant development. In this study, we reported the function of OsDCL1 in the immunity to rice blast, the devastating disease caused by the fungal pathogen, Magnaporthe oryzae. Expression profiling demonstrated that different OsDCLs responded dynamically and OsDCL1 reduced its expression upon the challenge of rice blast pathogen. In contrast, miR162a predicted to target OsDCL1 increased its expression, implying a negative feedback loop between OsDCL1 and miR162a in rice. In addition to developmental defects, the OsDCL1-silencing mutants showed enhanced resistance to virulent rice blast strains in a non-race specific manner. Accumulation of hydrogen peroxide and cell death were observed in the contact cells with infectious hyphae, revealing that silencing of OsDCL1 activated cellular defense responses. In OsDCL1 RNAi lines, 12 differentially expressed miRNAs were identified, of which 5 and 7 were down- and up-regulated, respectively, indicating that miRNAs responded dynamically in the interaction between rice and rice blast. Moreover, silencing of OsDCL1 activated the constitutive expression of defense related genes. Taken together, our results indicate that rice is capable of activating basal resistance against rice blast by perturbing OsDCL1-dependent miRNA biogenesis pathway.
High temperature (HT), high humidity (HH), and pathogen infection often co-occur and negatively affect plant growth. However, these stress factors and plant responses are generally studied in isolation. The mechanisms of synergistic responses to combined stresses are poorly understood. We isolated the subgroup IIb WRKY family member CaWRKY6 from Capsicum annuum and performed quantitative real-time PCR analysis. CaWRKY6 expression was upregulated by individual or simultaneous treatment with HT, HH, combined HT and HH (HTHH), and Ralstonia solanacearum inoculation, and responded to exogenous application of jasmonic acid (JA), ethephon, and abscisic acid (ABA). Virus-induced gene silencing of CaWRKY6 enhanced pepper plant susceptibility to R. solanacearum and HTHH, and downregulated the hypersensitive response (HR), JA-, ethylene (ET)-, and ABA-induced marker gene expression, and thermotolerance-associated expression of CaHSP24, ER-small CaSHP, and Chl-small CaHSP. CaWRKY6 overexpression in pepper attenuated the HTHH-induced suppression of resistance to R. solanacearum infection. CaWRKY6 bound to and activated the CaWRKY40 promoter in planta, which is a pepper WRKY that regulates heat-stress tolerance and R. solanacearum resistance. CaWRKY40 silencing significantly blocked HR-induced cell death and reduced transcriptional expression of CaWRKY40. These data suggest that CaWRKY6 is a positive regulator of R. solanacearum resistance and heat-stress tolerance, which occurs in part by activating CaWRKY40.
A rise in resistance to current antifungals necessitates strategies to identify alternative sources of effective fungicides. We report the discovery of poacic acid, a potent antifungal compound found in lignocellulosic hydrolysates of grasses. Chemical genomics using Saccharomyces cerevisiae showed that loss of cell wall synthesis and maintenance genes conferred increased sensitivity to poacic acid. Morphological analysis revealed that cells treated with poacic acid behaved similarly to cells treated with other cell wall-targeting drugs and mutants with deletions in genes involved in processes related to cell wall biogenesis. Poacic acid causes rapid cell lysis and is synergistic with caspofungin and fluconazole. The cellular target was identified; poacic acid localized to the cell wall and inhibited β-1,3-glucan synthesis in vivo and in vitro, apparently by directly binding β-1,3-glucan. Through its activity on the glucan layer, poacic acid inhibits growth of the fungi Sclerotinia sclerotiorum and Alternaria solani as well as the oomycete Phytophthora sojae. A single application of poacic acid to leaves infected with the broad-range fungal pathogen S. sclerotiorumsubstantially reduced lesion development. The discovery of poacic acid as a natural antifungal agent targeting β-1,3-glucan highlights the potential side use of products generated in the processing of renewable biomass toward biofuels as a source of valuable bioactive compounds and further clarifies the nature and mechanism of fermentation inhibitors found in lignocellulosic hydrolysates.
Ubiquitination regulates many processes in plants, including immunity. The E3 ubiquitin ligase PUB17 is a positive regulator of programmed cell death (PCD) triggered by resistance proteins CF4/9 in tomato. Its role in immunity to the potato late blight pathogen, Phytophthora infestans, was investigated here. Silencing StPUB17 in potato by RNAi and NbPUB17 in Nicotiana benthamiana by virus-induced gene silencing (VIGS) each enhanced P. infestans leaf colonization. PAMP-triggered immunity (PTI) transcriptional responses activated by flg22, and CF4/Avr4-mediated PCD were attenuated by silencing PUB17. However, silencing PUB17 did not compromise PCD triggered by P. infestans PAMP INF1, or co-expression of R3a/AVR3a, demonstrating that not all PTI- and PCD-associated responses require PUB17. PUB17 localizes to the plant nucleus and especially in the nucleolus. Transient over-expression of a dominant-negative StPUB17V314I,V316I mutant, which retained nucleolar localization, suppressed CF4-mediated cell death and enhanced P. infestans colonization. Exclusion of the StPUB17V314I,V316I mutant from the nucleus abolished its dominant-negative activity, demonstrating that StPUB17 functions in the nucleus. PUB17 is a positive regulator of immunity to late blight that acts in the nucleus to promote specific PTI and PCD pathways.
I really like this approach to writing review summary. The question is, how does material move between the ER and Golgi - through vesicles or through tubes? The answer isn't simple, as there are data to support both answers, and other possibilities as well. So, "in this article, four leading plant cell biologists attempted to resolve this issue. Unfortunately, their opinions are so divergent and often opposing that it was not possible to reach a consensus. Thus, we decided to let each tell his or her version individually."
Hyphal fusion is a ubiquitous phenomenon in filamentous fungi. Although morphological aspects of hyphal fusion during vegetative growth are well described, molecular mechanisms associated with self-signaling and the cellular machinery required for hyphal fusion are just beginning to be revealed. Genetic analyses suggest that signal transduction pathways are conserved between mating cell fusion in Saccharomyces cerevisiaeand vegetative hyphal fusion in filamentous fungi. However, the mechanism of self-signaling and the role of vegetative hyphal fusion in the biology of filamentous fungi require further study. Understanding hyphal fusion in model genetic systems, such as Neurospora crassa, provides a paradigm for self-signaling mechanisms in eukaryotic microbes and might also provide a model for somatic cell fusion events in other eukaryotic species.
Hyphal fusion (anastomosis) occurs at crucial stages during the life cycle of filamentous fungi and serves many important functions. During the vegetative phase, fusion initially occurs between spore germlings, and later on in the interior of the mature vegetative colony. Figure 1 shows the interconnected mycelial network of a fungal colony that results from multiple fusion events. It is widely assumed that vegetative hyphal fusion is important for intra-hyphal communication, translocation of water and nutrients, and general homeostasis within a colony 1 and 2. However, these predicted roles still need to be analyzed experimentally.
Terrific - Gina Kolata, science writer for the New York Times, looks at the new paper by Michael Palmgren's group out in Trends in Plant Science. They propose a new term, Rewilding, for introducing ancestral genes into today's crop to increase their resiliance to stress. Several other esteemed plant scientists are quoted in this very good story too.
I love the "top trumps" format for teaching. Here's a set of trumps cards designed by Dr Sarah McLusky about medicine from plants, which you can find on the SAPS site. http://www.saps.org.uk/…/871-medicines-and-drugs-from-plant…. Generic instructions for Top Trumps are here http://www.toptrumps.com/how-to-play-top-trumps/ You can also have students design their own top trumps card games - the topic can be plant species, proteins, amino acids, pigments, pathogens, nutrients, etc.
How do plant pathogens colonize their hosts is a key question in the field of plant pathology. Secreted effectors, hydrolytic enzymes, toxins and even small RNAs can be deployed as the virulence or pathogenicity factors to interfere with the host immune responses. But still there are more complicated systems to command and coordinate in their arsenal. The plant pathogen Fusarium graminearum can have devastating effects causing yield loss of various cereal crops and contaminating grain with mycotoxins that are harmful to the health of humans and livestock (Rocha et al., 2005). Given the economic importance of this pathogen, F. graminearum is currently under intense investigation and is becoming a model organism to study filamentous fungal cell biology, fungal–plant interactions and secondary metabolism. In this issue of New Phytologist, Yun et al. (pp. 119–134) contribute to our knowledge of the function of the F. graminearum phosphatome in hyphal growth, development, virulence and secondary metabolism by the omics level gene deletion and phenomic description (in line with the definition of kinome, phosphatome is the complete set of phosphatases of an organism, and the reversible protein phosphorylation is involved in the regulation of various life processes). Three phosphatases were identified as negative regulators of mitogen-activated protein kinase (MAPK) pathways.
Plants face several challenges by bacterial, fungal, oomycete, and viral pathogens during their life cycle. In order to defend against these biotic stresses, plants possess a dynamic, innate, natural immune system that efficiently detects potential pathogens and initiates a resistance response in the form of basal resistance and/or resistance (R)-gene-mediated defense, which is often associated with a hypersensitive response. Depending upon the nature of plant–pathogen interactions, plants generally have two main defense mechanisms, host resistance and nonhost resistance. Host resistance is generally controlled by single R genes and less durable compared with nonhost resistance. In contrast, nonhost resistance is believed to be a multi-gene trait and more durable. In this review, we describe the mechanisms of host and nonhost resistance against fungal and bacterial plant pathogens. In addition, we also attempt to compare host and nonhost resistance responses to identify similarities and differences, and their practical applications in crop improvement.
The nitrogen-fixing rhizobia in the symbiotic infected cells of root nodules are kept in membrane compartments derived from the host cell plasma membrane, forming what are known as symbiosomes. These are maintained as individual units, with mature symbiosomes having a specific radial position in the host cell cytoplasm. The mechanisms that adapt the host cell architecture to accommodate intracellular bacteria are not clear. The intracellular organization of any cell depends heavily on the actin cytoskeleton. Dynamic rearrangement of the actin cytoskeleton is crucial for cytoplasm organization and intracellular trafficking of vesicles and organelles. A key component of the actin cytoskeleton rearrangement is the ARP2/3 complex, which nucleates new actin filaments and forms branched actin networks. To clarify the role of the ARP2/3 complex in the development of infected cells and symbiosomes, we analyzed the pattern of actin microfilaments and the functional role of ARP3 in Medicago truncatula root nodules. In infected cells, ARP3 protein and actin were spatially associated with maturing symbiosomes. Partial ARP3 silencing causes defects in symbiosome development; in particular, ARP3 silencing disrupts the final differentiation steps in functional maturation into nitrogen-fixing units.
Secondary phloem and xylem tissues are produced through the activity of vascular cambium, the cylindrical secondary meristem which arises among the primary plant tissues.Despite its small size and herbaceous nature, Arabidopsis displays prominent secondary growth in several organs, including the root, hypocotyl and shoot. Together with the vast genetic resources and molecular research methods available for it, this has made Arabidopsis a versatile and accessible model organism for studying cambial development and wood formation.
L-type lectin receptor kinases (LecRKs) are potential immune receptors. Here we characterized two closely-related Arabidopsis LecRKs, LecRK-IX.1 and LecRK-IX.2, of which T-DNA insertion mutants showed compromised resistance to Phytophthora brassicae and Phytophthora capsici, with double mutants showing additive susceptibility. Overexpression of LecRK-IX.1 or LecRK-IX.2 in Arabidopsis and transient expression in N. benthamianaincreased Phytophthora resistance but also induced cell death. Phytophthora resistance required both the lectin domain and kinase activity, but for cell death the lectin domain was not needed. Silencing of the two closely related MAP kinase genes NbSIPK and NbNTF4 in N. benthamiana completely abolished LecRK-IX.1-induced cell death but not Phytophthoraresistance. LC-MS analysis of protein complexes co-immunoprecipitated in planta with LecRK-IX.1 or LecRK-IX.2 as bait, resulted in the identification of the N. benthamiana ABC transporter NbPDR1 as potential interactor of both LecRKs. The closest homolog of NbPDR1 in Arabidopsis is ABCG40 and co-immunoprecipitation experiments showed that ABCG40 associates with LecRK-IX.1 and LecRK-IX.2 in planta. Similar to the LecRK mutants, ABCG40 mutants showed compromised Phytophthora resistance. This study shows that LecRK-IX.1 and LecRK-IX.2 are Phytophthora resistance components that function independent of each other, and independent of the cell death phenotype. They both interact with the same ABC transporter suggesting that they exploit similar signal transduction pathways.
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