Legumes Protease Inhibitors as Biopesticides and Their Defense Mechanisms against Biotic Factors.

Legumes are affected by biotic factors such as insects, molds, bacteria, and viruses. These plants can produce many different molecules in response to the attack of phytopathogens. Protease inhibitors (PIs) are proteins produced by legumes that inhibit the protease activity of phytopathogens. PIs are known to reduce nutrient availability, which diminishes pathogen growth and can lead to the death of the pathogen. PIs are classified according to the specificity of the mechanistic activity of the proteolytic enzymes, with serine and cysteine protease inhibitors being studied the most. Previous investigations have reported the efficacy of these highly stable proteins against diverse biotic factors and the concomitant protective effects in crops, representing a possible replacement of toxic agrochemicals that harm the environment.

Ethylene Perception Is Associated with Methyl-Jasmonate-Mediated Immune Response against Botrytis cinerea in Tomato Fruit.

Jasmonic acid (JA)- and ethylene-mediated signaling pathways are reported to have synergistic effects on inhibiting gray mold. The present study aimed to explain the role of ethylene perception in methyl jasmonate (MeJA)-mediated immune responses. Results showed that exogenous MeJA enhanced disease resistance, accompanied by the induction of endogenous JA biosynthesis and ethylene production, which led to the activation of the phenolic metabolism pathway. Blocking ethylene perception using 1-methylcyclopropene (1-MCP) either before or after MeJA treatment could differently weaken the disease responses induced by MeJA, including suppressing the induction of ethylene production and JA contents and reducing activities of lipoxygenase and allene oxide synthase compared to MeJA treatment alone. Consequently, MeJA-induced elevations in the total phenolic content and the activities of phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, 4-coumarate:coenzyme A ligase, and peroxidase were impaired by 1-MCP. These results suggested that ethylene perception participated in MeJA-mediated immune responses in tomato fruit.

Hydrophobin HFBII-4 from Trichoderma asperellum induces antifungal resistance in poplar.

Herein, the class II hydrophobin gene HFBII-4 was cloned from the biocontrol agent Trichoderma asperellum ACCC30536 and recombinant rHFBII-4 was expressed in Pichia pastoris GS115. Treatment of Populus davidiana × P. alba var. pyramidalis (PdPap poplar) with rHFBII-4 altered the expression levels of genes in the auxin, salicylic acid (SA), and jasmonic acid (JA) signal transduction pathways. Polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) enzyme activities were induced with rHFBII-4. Evans Blue and nitro blue tetrazolium (NBT) staining indicated that cell membrane permeability and reactive oxygen species were lower in the leaves of plants treated with rHFBII-4. The chlorophyll content was higher than that of control at 2-5 days after treatment. Furthermore, poplar seedlings were inoculated with Alternaria alternata, disease symptoms were observed. The diseased area was smaller in leaves induced with rHFBII-4 compared with control. In summary, rHFBII-4 enhances resistance to A. alternata.

Crosstalk among Jasmonate, Salicylate and Ethylene Signaling Pathways in Plant Disease and Immune Responses.

Phytohormone crosstalk is crucial for plant defenses against pathogens and insects in which salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) play key roles. These low molecular mass signals critically trigger and modulate plant resistance against biotrophic as well as necrotrophic pathogens through a complex signaling network that even involves participation of other hormones. Crosstalk among SA, JA and ET is mediated by different molecular players, considered as integral part of these crosscommunicating signal transduction pathways. Recent progress has revealed that the positive versus negative interactions among those pathways ultimately enable a plant to fine-tune its defense against specific aggressors. On the other hand, pathogens have evolved strategies to manipulate the signaling network to their favour in order to intensify virulence on host plant. Here we review recent advances and current knowledge on the role of classical primary defense hormones SA, JA and ET as well as their synergistic and antagonistic interaction in plant disease and immune responses. Crosstalk with other hormones such as abscisic acid, auxin, brassinosteroids, cytokinins and melatonin is also discussed mainly in plant disease resistance. In addition to our keen focus on hormonal crosstalk, this review also highlights potential implication of positive and negative regulatory interactions for developing an efficient disease management strategy through manipulation of hormone signaling in plant.

N6-isopentenyladenosine, an endogenous isoprenoid end product, directly affects cytotoxic and regulatory functions of human NK cells through FDPS modulation.

iPA is a naturally occurring nucleoside with an isopentenyl moiety derived from the mevalonate pathway and a well-established anti-tumor activity. In analogy to the unique specificity for phosphoantigens, such as IPP, shown by human Vγ9Vδ2 T cells, here, we report for the first time the ability of iPA to selectively expand and directly target human NK cells. Interestingly, submicromolar doses of iPA stimulate resting human NK cells and synergize with IL-2 to induce a robust activation ex vivo with significant secretion of CCL5 and CCL3 and a large increase in TNF-α and IFN-γ production when compared with IL-2 single cytokine treatment. Moreover, iPA promotes NK cell proliferation and up-regulates the expression of specific NK cell-activating receptors, as well as CD69 and CD107a expression. Accordingly, this phenotype correlates with significantly greater cytotoxicity against tumor targets. At the molecular level, iPA leads to a selective, potent activation of MAPK signaling intermediaries downstream of the IL-2R. The effect results, at least in part, from the fine modulation of the FDPS activity, the same enzyme implicated in the stimulation of the human γδ T cells. The iPA-driven modulation of FDPS can cause an enhancement of post-translational prenylation essential for the biological activity of key proteins in NK signaling and effector functions, such as Ras. These unanticipated properties of iPA provide an additional piece of evidence of the immunoregulatory role of the intermediates of the mevalonate pathway and open novel therapeutic perspectives for this molecule as an immune-modulatory drug.

NaMYC2 transcription factor regulates a subset of plant defense responses in Nicotiana attenuata.

BACKGROUND: To survive herbivore attack, plants have evolved potent mechanisms of mechanical or chemical defense that are either constitutively present or inducible after herbivore attack. Due to the costs of defense deployment, plants often regulate their biosynthesis using various transcription factors (TFs). MYC2 regulators belong to the bHLH family of transcription factors that are involved in many aspects of plant defense and development. In this study, we identified a novel MYC2 TF from N. attenuata and characterized its regulatory function using a combination of molecular, analytic and ecological methods. RESULTS: The transcript and targeted metabolite analyses demonstrated that NaMYC2 is mainly involved in the regulation of the biosynthesis of nicotine and phenolamides in N. attenuata. In addition, using broadly-targeted metabolite analysis, we identified a number of other metabolite features that were regulated by NaMYC2, which, after full annotation, are expected to broaden our understanding of plant defense regulation. Unlike previous reports, the biosynthesis of jasmonates and some JA-/NaCOI1-dependent metabolites (e.g. HGL-DTGs) were not strongly regulated by NaMYC2, suggesting the involvement of other independent regulators. No significant differences were observed in the performance of M. sexta on MYC2-silenced plants, consistent with the well-known ability of this specialist insect to tolerate nicotine. CONCLUSION: By regulating the biosynthesis of nicotine, NaMYC2 is likely to enhance plant resistance against non-adapted herbivores and contribute to plant fitness; however, multiple JA/NaCOI1-dependent mechanisms (perhaps involving other MYCs) that regulate separate defense responses are likely to exist in N. attenuata. The considerable variation observed amongst different plant families in the responses regulated by jasmonate signaling highlights the sophistication with which plants craft highly specific and fine-tuned responses against the herbivores that attack them.

Unusual discrimination against carrier protein antibodies during partial purification of hapten-protein polyclonal antibodies to plant stress hormones.

Polyclonal antibodies (PcAb) were raised against t-zeatin riboside (t-ZR) and abscisic acid (ABA). t-ZR-BSA and ABA-BSA antibodies had high titre and specificity to haptens but also contained BSA specific antibodies as observed in double immuno diffusion and quantitative precipitation tests. Partial purification of antiserum by precipitation, desalting, and ion-exchange chromatography almost completely eliminated interference from BSA specific antibodies. Consequently, very little or no reaction was observed in dot-immunoblot assays even when high concentrations of BSA were probed with partially purified t-ZR-BSA IgG. Further studies with ABA antiserum showed that discrimination against BSA occurred during chromatography and not during salt fractionation. Because antibodies to both hapten and carrier protein were predominantly of IgG class, this unusual discrimination against carrier protein Ab was possibly influenced by two approaches followed for DEAE chromatography, viz. (i) adsorption of IgG at pH 8 followed by elution; or (ii) adsorption of contaminating proteins at neutral pH while specific IgG comes off as unbound fraction.

Purification of antibodies for the cytokinin N6-(delta 2-isopentenyl) adenosine by affinity chromatography.

Isopentenyl adenosine antibodies useful in the investigations of the "cytokinin" functions of isopentenyl adenosine were purified by affinity chromatography. Using different affinity columns, the antibodies were purified to near complete purity. Analyses of the purified proteins revealed the presence of isopentenyl adenosine binding proteins in normal rabbit serum, which presence supports a suggested role for isopentenyl adenosine and its related compounds in animal cell division in vivo.