Significance: Studies of the 1940s Victoria blight of oats epidemic discovered that some fungal pathogens secrete HSTs responsible for symptom development and specificity of the associated disease. The causal necrotrophic pathogen of Victoria blight, C. victoriae , secretes the peptide HST victorin, which was, subsequently, shown to constitute a novel class of effectors that exploit host immunity pathways aimed at repelling biotrophic pathogens. Although these discoveries have broadened our mechanistic understanding of plant-pathogen interactions, the genetic and biochemical origins of victorin have remained elusive. Here, we solve this decades-old mystery by demonstrating that victorin is produced ribosomally, not, as assumed, by nonribosomal peptide synthetase. Furthermore, we identify a CAO enzyme responsible for converting victorin to its active form.

Southern corn leaf blight (SCLB) caused by Cochliobolus heterostrophus is a destructive disease that threatens global maize ( Zea mays ) production. Despite many studies being conducted, very little is known about molecular processes employed by the pathogen during infection. There is a need to understand the fungal arms strategy and identify novel functional genes as targets for fungicide development. Transcriptome analysis based on RNA sequencing was carried out across conidia germination and host infection by C. heterostrophus . The present study revealed major changes in C. heterostrophus gene expression during host infection. Several differentially expressed genes (DEGs) induced during C. heterostrophus infection could be involved in the biosynthesis of secondary metabolites, peroxisome, energy metabolism, amino acid degradation and oxidative phosphorylation. In addition, histone acetyltransferase, secreted proteins, peroxisomal proteins, NADPH oxidase and transcription factors were selected for further functional validation. Here, we demonstrated that histone acetyltransferases (Hat2 and Rtt109), secreted proteins (Cel61A and Mep1), peroxisomal proteins (Pex11A and Pex14), NADPH oxidases (NoxA, NoxD and NoxR) and transcription factors (Crz1 and MtfA) play essential roles in C. heterostrophus conidiation, stress adaption and virulence. Taken together, our study revealed major changes in gene expression associated with C. heterostrophus infection and identified a diverse repertoire of genes critical for successful infection.

Klebsiella pneumoniae 2N3 is a strain of gram-negative bacteria that can degrade chlorimuron-ethyl and grow with chlorimuron-ethyl as the sole nitrogen source. The complete genome of Klebsiella pneumoniae 2N3 was sequenced using third generation high-throughput DNA sequencing technology. The genomic size of strain 2N3 was 5.32 Mb with a GC content of 57.33% and a total of 5156 coding genes and 112 non-coding RNAs predicted. Two hydrolases expressed by open reading frames (ORFs) 0934 and 0492 were predicted and experimentally confirmed by gene knockout to be involved in the degradation of chlorimuron-ethyl. Strains of ΔORF 0934, ΔORF 0492, and wild type (WT) reached their highest growth rates after 8–10 hours in incubation. The degradation rates of chlorimuron-ethyl by both ΔORF 0934 and ΔORF 0492 decreased in comparison to the WT during the first 8 hours in culture by 25.60% and 24.74%, respectively, while strains ΔORF 0934, ΔORF 0492, and the WT reached the highest degradation rates of chlorimuron-ethyl in 36 hours of 74.56%, 90.53%, and 95.06%, respectively. This study provides scientific evidence to support the application of Klebsiella pneumoniae 2N3 in bioremediation to control environmental pollution.