Project description:Gray leaf spot (GLS) disease of maize can be caused by either of two sibling fungal species Cercospora zeina or Cercospora zeae-maydis. These species differ in geographical distribution, for example to date only C. zeina is associated with GLS in Africa. C. zeae-maydis isolates produce the phytotoxin cercosporin in vitro, whereas C. zeina does not. C.zeina was grown in different in vitro conditions to determine if the cercosporin biosynthesis genes were expressed. Furthermore, the choice of a range of different in vitro conditions was aimed at capturing transcript sequences from a broad range of genes to aid in identification of gene models for annotation of the C.zeina genome sequence.
Project description:Purpose: The aim was to compare the transcriptome (using RNASeq) of a Cercospora zeina-resistant line (RIL387) and a Cercospora zeina susceptible line (RIL165), following inoculation by Cercospora zeina, in order to identify the defense responses associated with each line. Methods: Plants were grown in rows in three randomised blocks. Natural infection with Cercospora zeina was allowed to take place. Infected leves were harvested at the R5-early dent stage. Three leaves (one per plant) were harvested per block and pooled to make up one biological rep. One biological rep was harvested per block for each line. RNA was extracted and sequenced using Illumina. Sequencing reads were mapped to the B73 reference genome and were analysed using the Tuxedo suite of tools (Top hat, Cufflinks, Cuffmerge and Cuffdiff). Results: 5349 genes were differentially expressed between RIL165 and RIL387. In order to dissect responses specific to RIL165 and RIL387, 2394 genes with Log2FC ≤-1 were defined as having higher expression in RIL165 compared to RIL387 and 1393 genes with a Log2FC ≥1 as having increased expression in RIL387 compared to RIL165. Nine genes were validated using RT-qPCR. Four reference genes were included in the RT-qPCR analysis. Differentially expressed genes were further analysed for GO enrichment and pathway representation. Conclusions: Our RNA-Seq results show that a resistant and susceptible line repond differently to infection with Cercospora zeina, as differentially expressed genes were identified between the two lines.
Project description:Plants often generate secondary metabolites with antifungal properties as defense mechanisms against parasites. Although some fungi may potentially overcome the barrier of antimicrobial compounds, only a limited number of examples and molecular mechanisms of resistance have been reported. Here, we found an Aglaia plant-parasitizing fungus that overcomes the toxicity of rocalgates, which are translation inhibitors synthesized by the plant, through an amino acid substitution in a translation initiation factor (eIF). De novo transcriptome assembly of the fungus revealed that eIF4A, a molecular target of rocaglates, replaces a critical amino acid in the rocaglate binding site. Moreover, genome-wide ribosome profiling harnessing a cucumber-infecting fungus, Colletotrichum orbiculare, demonstrated that the translational inhibitory effects of rocaglates were largely attenuated by the mutation found in the Aglaia parasite. The engineered Colletotrichum orbiculare showed a survival advantage on cucumber plants with rocaglates. Our study exemplifies a plant-fungus tug-of-war centered on secondary metabolites produced by host plants.