Project description:Native host plant insect resistance in the maize inbred line Mp708 was developed by traditional plant breeding. Resistant Mp708 thwarts feeding by fall armyworm (Spodoptera frugiperda [J.E. Smith]; Lepidoptera: Noctuidae), numerous other lepidopteran pests, and the coleopteran western corn rootworm. This broad resistance makes it an excellent model for studying native host plant resistance mechanisms. In response to caterpillar feeding, Mp708 rapidly mobilizes Mir1-CP, a unique cysteine protease that appears to translocate from roots to the maize midwhorl where it accumulates. This accumulation correlates with a significant reduction in caterpillar growth resulting from diminished food utilization. In addition, the peritrophic membrane (PM) that surrounds the food bolus in the mudgut (MG) is severely damaged in caterpillars fed on sweet corn callus transformed to express the gene encoding Mir1-CP or on midwhorl tissue from resistant Mp708 maize. Functions of the PM include assisting digestion and protecting the epithelium of the caterpillar MG from physical and chemical damage. Consequently, the reduced growth of caterpillars that feed on Mp708 is probably due to the action of Mir1-CP on PM physiology. In fact, previous in vitro studies indicated that Mir1-CP was capable of permeabilizing the PM. The present study used both targeted (qRT-PCR) and global (mRNA-seq) transcriptome analyses to explore the effect of eating Mir1-CP expressing Mp708 maize on abundance of transcripts in the MG of fall armyworm larvae in comparison to MGs from larvae fed on susceptible Tx601 maize that does not express Mir1-CP. Expression of genes encoding proteins involved in PM production is upregulated in MGs from fall armyworm fed on Mp708. Also, several digestive enzymes (endopeptidases, aminopeptidases, lipases, amylase) were more highly expressed in MGs from larvae fed on Mp708 than MGs from larvae fed on Tx601. Impaired growth of larvae fed on Mp708 probably results from metabolic costs associated with higher production of PM constituents and digestive enzymes in a compensatory attempt to maintain MG function.
Project description:The extreme generalist two-spotted spider mite, Tetranychus urticae, which is documented to feed on more than 1100 plant hosts, is becoming an increasingly important agricultural pest. Historically, as studies of plant-herbivore interactions have focused largely on insects, considerably less research has investigated plant responses to spider mite herbivores, especially in grasses. To identify intraspecific differences in maize response to T. urticae, we collected RNA-seq data from three maize (Zea mays) inbred lines (B73, B75 and B49) as well as two F1 lines arising from crosses between B73 x B75 and B73 x B96. For each maize line, RNA-seq data was collected from uninfested leaves (control) and leaves infested with T. urticae for 24 hours.
Project description:Native host plant insect resistance in the maize inbred line Mp708 was developed by traditional plant breeding. Resistant Mp708 thwarts feeding by fall armyworm (Spodoptera frugiperda [J.E. Smith]; Lepidoptera: Noctuidae), numerous other lepidopteran pests, and the coleopteran western corn rootworm. This broad resistance makes it an excellent model for studying native host plant resistance mechanisms. In response to caterpillar feeding, Mp708 rapidly mobilizes Mir1-CP, a unique cysteine protease that appears to translocate from roots to the maize midwhorl where it accumulates. This accumulation correlates with a significant reduction in caterpillar growth resulting from diminished food utilization. In addition, the peritrophic membrane (PM) that surrounds the food bolus in the mudgut (MG) is severely damaged in caterpillars fed on sweet corn callus transformed to express the gene encoding Mir1-CP or on midwhorl tissue from resistant Mp708 maize. Functions of the PM include assisting digestion and protecting the epithelium of the caterpillar MG from physical and chemical damage. Consequently, the reduced growth of caterpillars that feed on Mp708 is probably due to the action of Mir1-CP on PM physiology. In fact, previous in vitro studies indicated that Mir1-CP was capable of permeabilizing the PM. The present study used both targeted (qRT-PCR) and global (mRNA-seq) transcriptome analyses to explore the effect of eating Mir1-CP expressing Mp708 maize on abundance of transcripts in the MG of fall armyworm larvae in comparison to MGs from larvae fed on susceptible Tx601 maize that does not express Mir1-CP. Expression of genes encoding proteins involved in PM production is upregulated in MGs from fall armyworm fed on Mp708. Also, several digestive enzymes (endopeptidases, aminopeptidases, lipases, amylase) were more highly expressed in MGs from larvae fed on Mp708 than MGs from larvae fed on Tx601. Impaired growth of larvae fed on Mp708 probably results from metabolic costs associated with higher production of PM constituents and digestive enzymes in a compensatory attempt to maintain MG function. Beginning as neonates, fall armyworm larvae used in the mRNA-seq experiment were reared on yellow-green midwhorl foliage from resistant Mp708 maize or susceptible Tx601 maize. Old foliage and frass were removed every other day and replaced with fresh foliage. Larvae were reared in an environmental chamber at 27M-BM-0C, 14:10 (light:dark) photoperiod, and 70% relative humidity. Midguts were dissected from larvae 2 d after molting to the last instar with masses between 300 and 400 mg. Dissections were done with cold anesthetized larvae submerged in Bombyx saline. After removing Malpighian tubules, foregut anterior to the stomodial valve, hindgut and food bolus, the MG was transferred from the body cavity, rinsed well with cold saline, and preserved in RNAlaterM-BM-.. Equal amounts (3 M-BM-5g) of total RNA from an individual MG were randomly pooled into three replicates per treatment (i.e., Mp708 or Tx601) such that each treatment replicate derived from 12-13 MGs. Each pool of total RNA was separately enriched for poly(A+) RNA and submitted to the Penn State Genomics Core Facility (University Park, PA) where barcoded cDNA libraries were prepared and equimolar quantities of each library sequenced on the SOLiD 3 Plus System. Sequence reads were filtered to accept reads whose median score threshold was M-bM-^IM-%12, contained M-bM-^IM-%25 bases and contained one or more bases with a quality score M-bM-^IM-%14. The 138911 Sanger ESTs in SPODOBASE (http://bioweb.ensam.inra.fr/spodobase) were assembled into a reference transcriptome using SeqMan Pro version 8.0.2. Filtered reads from each library representing a replicate within a maize inbred treatment were mapped separately to the reference transcriptome using the Bowtie-like algorithm in NextGENeM-BM-. with the requirement that 85% of 12 or more nucleotides comprising a read must match the reference. A read was allowed to map only once (i.e., no ambiguous mapping). The number of mapped reads per contig (i.e., gene model) in each treatment replicate-library were summed by NextGENeM-BM-. as read counts per gene and subsequently used in differential expression analyses.
Project description:Soil waterlogging is one of the major abiotic stresses affecting maize growth and yields. To understand the molecular mechanisms underlying waterlogging tolerance in maize, the iTRAQ LC-MS/MS technique was employed to map the proteome of seedling root cells of the A3237 (tolerant inbred) and A3239 (sensitive inbred) lines under control and waterlogged conditions. Among the 3373 identified proteins, 293 were differentially abundant proteins (DAPs), of which 207 originated in A3237 and 158 in A3239. These DAPs were categorized into 11 groups that are closely related to plant defence responses, including metabolism, energy, disease/defense and transport. In the tolerant line A3237, NADP-malic enzyme, glutamate decarboxylase, coproporphyrinogen III oxidase, glutathione S-transferase TAU 25, glutathione dehydrogenase and xyloglucan endotransglycosylase 6 were specifically accumulated to manage energy, maintain pH levels and minimize oxidative damage in waterlogged root cells.
Project description:We demonstrated the manifestation of heterosis in hybrid maize embryo and endosperm tissue six days after fertilization in crosses of several inbred lines. Here we analyzed heterosis-associated gene expression pattern in these tissues of reciprocal crosses of two european maize inbred line combinations. Differences in gene expression were analyzed with custom microarrays by a combined approach of suppression subtractive hybridization and microarray hybridizations
Project description:Spider mites, including the two-spotted spider mite (Tetranychus urticae, TSSM) and the Banks grass mite (Oligonychus pratensis, BGM), are becoming increasingly important agricultural pests. The TSSM is an extreme generalist documented to feed on more than 1100 plant hosts. In contrast, the BGM is a grass specialist, with hosts including important cereal crops like maize, wheat, and sorghum. Historically, studies of plant-herbivore interactions have focused largely on insects. As such, far less is known about plant responses to spider mite herbivores, especially in grasses, and whether responses differ between generalist and specialist mites. To identify plant defense pathways responding to spider mites, we collected time course RNA-seq data from maize (Zea mays) infested with TSSMs and BGMs. Additionally, and as a comparison to the physical damage caused by spider mite feeding, a wounding treatment was also included. In total, four biological samples were generated per treatment.
Project description:Deploying toxins in complex mixtures is thought to be advantageous and is observed during antagonistic interactions in nature. Toxin mixtures are widely utilized in medicine and pest control, as they are thought to slow the evolution of detoxification counterresponses in the targeted organisms. Here we show that caterpillars rearrange key constituents of two distinct plant defense pathways to postingestively disable the defensive properties of both pathways. Specifically, phenolic esters of quinic acid, chlorogenic acids (CAs), potent herbivore and ultraviolet (UV) defenses, are reesterified to decorate particular sugars of 17-hydroxygeranyllinalool diterpene glycosides (HGL-DTGs) and prevent their respective anti–herbivore defense functions. This was discovered through the employment of comparative metabolomics of the leaves of Nicotiana attenuata and the frass of this native tobacco’s specialist herbivore, Manduca sexta larvae. Feeding caterpillars on leaves of transgenic plants abrogated in each of the two pathways, separately and together, revealed that one of the fully characterized frass conjugates, caffeoylated HGL-DTG, originated from ingested CA and HGL-DTGs and that both had negative effects on the defensive function of the other compound class, as revealed by rates of larval mass gain. This negative defensive synergy was further explored in 183 N. attenuata natural accessions, which revealed a strong negative covariance between the two defense pathways. Further mapping analyses in a biparental recombinant inbred line (RIL) population imputed quantitative trait loci (QTLs) for the two pathways at distinct genomic locations. The postingestive repurposing of defense metabolism constituents reveals a downside of deploying toxins in mixtures, a downside which plants in nature have evolved to counter.
Project description:Diversification of effector function, driven by a co-evolutionary arms race, enables pathogens to establish compatible interactions with hosts. Structurally conserved plant pathogenesis-related PR-1 and PR-1-like (PR-1L) proteins are involved in plant defense and fungal virulence, respectively. It is unclear how fungal PR-1L counters plant defense. Here, we show that Ustilago maydis UmPR-1La and yeast ScPRY1, with conserved phenolic resistance functions, are Ser/Thr-rich region-mediated cell-surface localization proteins. However, UmPR-1La has gained specialized activity in sensing phenolics and eliciting hyphal-like formation to guide fungal growth in plants. Additionally, U. maydis hijacks maize cathepsin B-like 3 (CatB3) to release functional CAPE-like peptides by cleaving UmPR-1La’s conserved CNYD motif, subverting plant CAPE-primed immunity and promoting fungal virulence. Surprisingly, CatB3 avoids cleavage of plant PR-1s, despite the presence of the same conserved CNYD motif. Our work highlights that UmPR-1La has acquired additional dual roles to suppress plant defense and sustain the infection process of fungal pathogens.