Project description:PP2Cs represent the largest gene family of protein phosphatases. Current research has predominantly focused on the regulation of the PP2C.A family in the abscisic acid (ABA) signaling pathway. However, there is currently no documented research regarding the involvement of PP2Cs in plant responses to biotic stressors. In this study, we found that maize (Zea may) ZmPP2C45 is an essential but insufficient negative regulator of benzoxazinoids. Since BZXs are important defensive metabolites against insect herbivores, we hypothesized that the genetic knock-out of ZmPP2C45 could affect the performance of insect herbivores on these plants.To further investigate how ZmPP2C45 depleted BZX contents, we performed a comparative transcriptomics analysis on the Zmpp2c45 mutants and the wildtype control. As a result, 789 genes were found significantly up-regulated in the mutant plants, whereas 198 genes were down-regulated. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed that BZX biosynthesis-related genes were over-represented among the up-regulated genes in the Zmpp2c45 plants
Project description:Feeding by Spodoptera exigua (beet armyworm) larvae on Zea mays (maize) induces expression of 9-lipoxygenases to a greater extent than 13-lipoxygenases. Whereas 13-lipoxygenases have an established role in the synthesis of jasmonates that serve as defense signaling molecules in many plant species, relatively little is known about the role of 9-lipoxygenases in herbivore defense. Phylogenetic analysis of lipoxygenases from maize inbred lines B73 and W22 shows that, although most Lox genes are present in both lines, Lox12, a 9-lipoxygenase that has been implicated in fungal defense, is truncated and unlikely to encode a functional protein in W22. Two independent Mutator transposon insertions in another 9-lipoxygenase, Lox4, caused improved S. exigua growth on the mutant lines relative to wildtype W22. This observation suggests a function in herbivore defense for metabolic products downstream of maize Lox4, either through direct toxicity or a perhaps an as yet unknown signaling function.
Project description:Plant volatiles can mediate plant-plant communication in the sense that plants attacked by herbivores can signal their unattacked neighbors of danger by emitting HIPVs. We call this the priming effect. Since the plant defense response is a systematic process involving numerous pathways and genes,to characterize the priming process, a time course study using a genome-wide microarray may provide more accurate information about the priming process. Furthermore, to what extent do the priming process and direct defense share similar gene expression profiles or pathways are also not clear. We used microarray to detect the priming effect of plant volatiles to healthy Arabidopsis thaliana, and the effect of direct leafminer feeding to Arabidopsis thalianas.
Project description:Stalk borers are major pests for some of the most important crops in the world, such as maize or rice. Plant defense mechanisms against these herbivores have been poorly investigated. The maize´s stalk responds to insect feeding activating defense genes including hormone biosynthetic-related or proteinase inhibitor transcripts. The most outstanding conclusion is that cells in the maize´s stalk undergo cell wall fortification after corn borer tunneling. We performed a gene expression profiling to identify those genes differentially expressed in maize after infestation with the corn borer S. nonagrioides.
Project description:Tomato plants are commonly attacked by herbivorous mites, including by generalist Tetranychus urticae and specialists Tetranychus evansi and Aculops lycopersici. Mite feeding induces plant defense responses that reduce mite performance. However, via poorly understood mechanisms, T. evansi and A. lycopersici suppress plant defenses and, consequently, maintain a high performance on tomato. Accordingly, on a shared host, non-adapted T. urticae can be facilitated by either of the specialist mites, likely via the suppression of plant defenses. To better understand defense suppression and indirect plant-mediated interactions between herbivorous mites, we used microarrays to analyze transcriptomic changes in tomato after attack by either a single mite species (T. urticae, T. evansi, A. lycopersici) or two species simultaneously (T. urticae plus T. evansi or T. urticae plus A. lycopersici). Additionally, we assessed mite-induced changes in defense-associated phytohormones using LC-MS/MS. Compared to non-infested controls, jasmonates (JAs) and salicylate (SA) accumulated to higher amounts upon all mite-infestation treatments, but lowest increases were detected after single infestations with defense-suppressors. Strikingly, whereas 8 to 10% of tomato genes was differentially expressed upon single infestations with T. urticae or A. lycopersici, only 0.1% was altered in T. evansi-infested plants. Transcriptome analysis of dual-infested leaves revealed that T. evansi dampened T. urticae-triggered host responses on a genome-wide scale, while A. lycopersici primarily suppressed T. urticae-induced JA defenses. Our results provide valuable new insights into the mechanisms underlying host defense suppression and the plant-mediated facilitation of competing herbivores.
Project description:Plant volatiles can mediate plant-plant communication in the sense that plants attacked by herbivores can signal their unattacked neighbors of danger by emitting HIPVs. We call this the priming effect. Since the plant defense response is a systematic process involving numerous pathways and genes,to characterize the priming process, a time course study using a genome-wide microarray may provide more accurate information about the priming process. Furthermore, to what extent do the priming process and direct defense share similar gene expression profiles or pathways are also not clear. We used microarray to detect the priming effect of plant volatiles to healthy Arabidopsis thaliana, and the effect of direct leafminer feeding to Arabidopsis thalianas. A system using Lima bean plants, from which HIPVs can be effectively induced by leafminer feeding, as emitters and Arabidopsis thaliana as receivers is used to track the priming process between neighbor plants. The Arabisopsis thaliana seedlings were treated by volatiles from leafminer fed lima bean for 24h or 48h for RNA extraction and hybridization on Affymetrix microarrays. The Arabisopsis thaliana seedlings fed by leafminer directly were also collected The for RNA extraction and hybridization on Affymetrix micorarrays. We want to explore the response of Arabidopsis thaliana to priming volatiles during a 24h-48h time course. We also want to compare the effect of priming and direct leafminer feeding.
Project description:Most plant viruses are vectored by insects and the interactions of virus-plant-vector have important ecological and evolutionary implications. Insect vectors often perform better on virus-infected plants. This indirect mutualism between plant viruses and insect vectors promotes the spread of virus and has significant agronomical effects. However, few studies have investigated how plant viruses manipulate plant defenses and promote vector performance. Begomoviruses are a prominent group of plant viruses in tropical and sub-tropical agro-ecosystems and are transmitted by whiteflies. Working with the whitefly Bemisia tabaci, begomoviruses and tobacco, we revealed that C2 protein of begomoviruses lacking DNA satellites was responsible for the suppression of plant defenses against whitefly vectors. We found that infection of plants by tomato yellow leaf curl virus (TYLCV), one of the most devastating begomoviruses worldwide, promoted the survival and reproduction of whitefly vectors. TYLCV C2 protein suppressed plant defenses by interacting with plant ubiquitin. This interaction compromised the degradation of JAZ1 protein, thus inhibiting jasmonic acid defense and the expression of MYC2-regulated terpene synthase genes. We further demonstrated that function of C2 protein among begomoviruses not associated with satellites is well conserved and ubiquitination is an evolutionarily conserved target of begomoviruses for the suppression of plant resistance to whitefly vectors. Taken together, these results demonstrate that ubiquitination inhibition by begomovirus C2 protein might be a general mechanism in begomovirus, whitefly and plant interactions.
Project description:Specialized metabolites provide important layers of biochemical immunity underlaying crop resistance; however, challenges in resolving pathways limit applications. To understand maize (Zea mays) antibiotics imparting disease resistance we integrated large-scale transcriptomic patterns, association mapping, enzyme assays, proteomics, structure elucidation and targeted mutagenesis. Three zealexin (Zx) gene clusters (GC) comprised of 4 sesquiterpene synthases (GC1:Zx1-4) and 6 cytochrome P450s in the Cyp71Z (GC2:Zx5-7) and Cyp81E (GC3:Zx8-10) families drive the production diverse antibiotic cocktails. Gene duplications ensure pathway resiliency to single null mutations while promiscuous enzymes constitute a biosynthetic hourglass pathway acting on diverse endogenous substrates to drive additional antibiotic complexity. Zx pathway activation mediating pathogen resistance occurs during a dramatic reorganization of >50% of the measurable proteome. Understanding the genetic basis of specialized metabolic pathways structured to maintain disease resistance provides a conceptual foundation for transferring durable biochemical immunity between plants.
Project description:Gene duplication is a major source of plant chemical diversity that mediates plant-herbivore interactions. There is little direct evidence, however, that novel chemical traits arising from gene duplication reduce herbivory. Higher plants use threonine deaminase (TD) to catalyze the dehydration of threonine (Thr) to ?-ketobutyrate and ammonia as the committed step in the biosynthesis of isoleucine (Ile). Cultivated tomato and related Solanum species contain a duplicated TD paralog (TD2) that is coexpressed with a suite of genes involved in herbivore resistance. Analysis of TD2-deficient tomato lines showed that TD2 has a defensive function related to Thr catabolism in the gut of lepidopteran herbivores. During herbivory, the regulatory domain of TD2 is removed by proteolysis to generate a truncated protein (pTD2) that efficiently degrades Thr without being inhibited by Ile. We show that this proteolytic activation step occurs in the gut of lepidopteran but not coleopteran herbivores, and is catalyzed by a chymotrypsin-like protease of insect origin. Analysis of purified recombinant enzymes showed that TD2 is remarkably more resistant to proteolysis and high temperature than the ancestral TD1 isoform. The crystal structure of pTD2 provided evidence that electrostatic interactions constitute a stabilizing feature associated with adaptation of TD2 to the extreme environment of the lepidopteran gut. These findings demonstrate a role for gene duplication in the evolution of a plant defense that targets and co-opts herbivore digestive physiology.