Transcriptome profiling of two maize inbreds with distinct responses to Gibberella ear rot disease to identify candidate resistance genes

Abstract Background Gibberella ear rot (GER) is one of the most economically important fungal diseases of maize in the temperate zone due to moldy grain contaminated with health threatening mycotoxins. To develop resistant genotypes and control the disease, understanding the host-pathogen interaction is essential. Results RNA-Seq-derived transcriptome profiles of fungal- and mock-inoculated developing kernel tissues of two maize inbred lines were used to identify differentially expressed transcripts and propose candidate genes mapping within GER resistance quantitative trait loci (QTL). A total of 1255 transcripts were significantly (P ≤ 0.05) up regulated due to fungal infection in both susceptible and resistant inbreds. A greater number of transcripts were up regulated in the former (1174) than the latter (497) and increased as the infection progressed from 1 to 2 days after inoculation. Focusing on differentially expressed genes located within QTL regions for GER resistance, we identified 81 genes involved in membrane transport, hormone regulation, cell wall modification, cell detoxification, and biosynthesis of pathogenesis related proteins and phytoalexins as candidate genes contributing to resistance. Applying droplet digital PCR, we validated the expression profiles of a subset of these candidate genes from QTL regions contributed by the resistant inbred on chromosomes 1, 2 and 9. Conclusion By screening global gene expression profiles for differentially expressed genes mapping within resistance QTL regions, we have identified candidate genes for gibberella ear rot resistance on several maize chromosomes which could potentially lead to a better understanding of Fusarium resistance mechanisms

Additional file 2: Figure S1. of Transcriptome profiling of two maize inbreds with distinct responses to Gibberella ear rot disease to identify candidate resistance genes

Comparison between ddPCR and RNA-Seq expression profiles of selected genes. The Y-axis scale corresponds to transcripts per million (TPM) for RNA-Seq data and copies/Îźl for ddPCR. Tissue samples from the 2004 and 2006 field season were used for both gene expression quantitation methods. (PDF 288 kb

Additional file 1: Table S1. of Transcriptome profiling of two maize inbreds with distinct responses to Gibberella ear rot disease to identify candidate resistance genes

Primers used for selected candidate and reference genes in droplet digital PCR validation experiment. Table S2. Hourly temperature readings during inoculation and tissue collection time periods in 2004, 2006, and 2013. Table S3. Mapping of RNA-Seq reads to the reference genome B73 V2. Table S4. List of significant differentially expressed transcripts. Table S5. Upregulated transcripts mapping within GER resistance QTL regions. (XLSX 1156 kb

Hydroxylation of longiborneol by a Clm2-encoded CYP450 monooxygenase to produce culmorin in Fusarium graminearum

A second structural gene required for culmorin biosynthesis in the plant pathogen Fusarium graminearum is described. Clm2 encodes a regio- and stereoselective cytochrome P450 monooxygenase for C-11 of longiborneol. Clm2 gene disruptants were grown in liquid culture and assessed for culmorin production via HPLC-evaporative light scattering detection. The analysis indicated a complete loss of culmorin from the liquid culture of the \u394Clm2 mutants. Culmorin production resumed in a \u394Clm2 complementation experiment. A detailed analysis of the secondary metabolites extracted from the large-scale liquid culture of disruptant \u394Clm2D20 revealed five new natural products: 3-hydroxylongiborneol, 5-hydroxylongiborneol, 12-hydroxylongiborneol, 15-hydroxylongiborneol, and 11-epi-acetylculmorin. The structures of the new compounds were elucidated by a combination of HRMS, 1D and 2D NMR, and X-ray crystallography.Peer reviewed: YesNRC publication: Ye

Diverse developmental mutants revealed in an activation-tagged population of poplar

We have produced the largest population of activation-tagged poplar trees to date, approximately 1800 independent lines, and report on phenotypes of interest that have been identified in tissue culture and greenhouse conditions. Activation tagging is an insertional mutagenesis technique that results in the dominant upregulation of an endogenous gene. A large-scale Agrobacterium-mediated transformation protocol was used to transform the pSKI074 activation-tagging vector into Populus tremula × Populus alba hybrid poplar. We have screened the first 1000 lines for developmental abnormalities and have a visible mutant frequency of 2.4%, with alterations in leaf and stem structure as well as overall stature. Most of the phenotypes represent new phenotypes that have not previously been identified in poplar and, in some cases, not in any other plant either. Molecular analysis of the T-DNA inserts of a subpopulation of mutant lines reveal both single and double T-DNA inserts with double inserts more common in lines with visible phenotypes. The broad range of developmental mutants identified in this pilot screen of the population reveals that it will be a valuable resource for gene discovery in poplar. The full value of this population will only be realized as we screen these lines for a wide range of phenotypes

CO476 corn inbred line

CO476 is an early-medium maturity (76 d to flowering), mostly stiff stalk (BSSS), yellow flint inbred which combines well with a stiff stalk B14-type and Iodent-type testers in many different locations. CO476 possesses moderate resistance to gibberella ear rot both in the inbred and in hybrid combinations. It has intermediate response to common smut, Fusarium stalk rot, northern corn leaf blight, common rust, and Goss’s wilt.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Hydroxylation of Longiborneol by a <i>Clm2</i>-Encoded CYP450 Monooxygenase to Produce Culmorin in <i>Fusarium graminearum</i>

A second structural gene required for culmorin biosynthesis in the plant pathogen <i>Fusarium graminearum</i> is described. <i>Clm2</i> encodes a regio- and stereoselective cytochrome P450 monooxygenase for C-11 of longiborneol (<b>1</b>). <i>Clm2</i> gene disruptants were grown in liquid culture and assessed for culmorin production via HPLC-evaporative light scattering detection. The analysis indicated a complete loss of culmorin (<b>2</b>) from the liquid culture of the Δ<i>Clm2</i> mutants. Culmorin production resumed in a Δ<i>Clm2</i> complementation experiment. A detailed analysis of the secondary metabolites extracted from the large-scale liquid culture of disruptant Δ<i>Clm2</i>D20 revealed five new natural products: 3-hydroxylongiborneol (<b>3</b>), 5-hydroxylongiborneol (<b>4</b>), 12-hydroxylongiborneol (<b>5</b>), 15-hydroxylongiborneol (<b>6</b>), and 11-<i>epi</i>-acetylculmorin (<b>7</b>). The structures of the new compounds were elucidated by a combination of HRMS, 1D and 2D NMR, and X-ray crystallography

A cyclic lipopeptide from Fusarium graminearum targets plant membranes to promote virulence

Summary: Microbial plant pathogens deploy amphipathic cyclic lipopeptides to reduce surface tension in their environment. While plants can detect these molecules to activate cellular stress responses, the role of these lipopeptides or associated host responses in pathogenesis are not fully clear. The gramillin cyclic lipopeptide is produced by the Fusarium graminearum fungus and is a virulence factor and toxin in maize. Here, we show that gramillin promotes virulence and necrosis in both monocots and dicots by disrupting ion balance across membranes. Gramillin is a cation-conducting ionophore and causes plasma membrane depolarization. This disruption triggers cellular signaling, including a burst of reactive oxygen species (ROS), transcriptional reprogramming, and callose production. Gramillin-induced ROS depends on expression of host ILK1 and RBOHD genes, which promote fungal induction of virulence genes during infection and host susceptibility. We conclude that gramillin’s ionophore activity targets plant membranes to coordinate attack by the F. graminearum fungus