Plant Defense Mechanisms Are Activated during Biotrophic and Necrotrophic Development of Colletotricum graminicola in Maize    

Abstract

Hemibiotrophic plant pathogens first establish a biotrophic interaction with the host plant and later switch to a destructive necrotrophic lifestyle. Studies of biotrophic pathogens have shown that they actively suppress plant defenses after an initial microbe-associated molecular pattern-triggered activation. In contrast, studies of the hemibiotrophs suggest that they do not suppress plant defenses during the biotrophic phase, indicating that while there are similarities between the biotrophic phase of hemibiotrophs and biotrophic pathogens, the two lifestyles are not analogous. We performed transcriptomic, histological, and biochemical studies of the early events during the infection of maize (Zea mays) with Colletotrichum graminicola, a model pathosystem for the study of hemibiotrophy. Time-course experiments revealed that mRNAs of several defense-related genes, reactive oxygen species, and antimicrobial compounds all begin to accumulate early in the infection process and continue to accumulate during the biotrophic stage. We also discovered the production of maize-derived vesicular bodies containing hydrogen peroxide targeting the fungal hyphae. We describe the fungal respiratory burst during host infection, paralleled by superoxide ion production in specific fungal cells during the transition from biotrophy to a necrotrophic lifestyle. We also identified several novel putative fungal effectors and studied their expression during anthracnose development in maize. Our results demonstrate a strong induction of defense mechanisms occurring in maize cells during C. graminicola infection, even during the biotrophic development of the pathogen. We hypothesize that the switch to necrotrophic growth enables the fungus to evade the effects of the plant immune system and allows for full fungal pathogenicity.

Identification of positive selection in disease response genes within members of the Poaceae

“…In a previous study, we performed suppression subtractive hybridization experiments in the maize-Colletotrichum graminicola pathosystem during early stages of anthracnose leaf blight development. 6 We found more than 200 differentially expressed genes from maize, including 36 DRGs and 34 genes encoding hypothetical or unknown proteins (HUPGs) identified as upregulated during infection. Moreover, the recent release Millions of years of coevolution between plants and pathogens can leave footprints on their genomes and genes involved on this interaction are expected to show patterns of positive selection in which novel, beneficial alleles are rapidly fixed within the population.…”

“…6,9,10 These genes induced during infection with both fungal species may represent evolutionary innovations in the maize genome directly related with defense mechanisms and are very interesting candidates for future functional characterization.…”

“…6 Finally, cluster 31477240-se showed three sites with ω > 1 using M8+BEB, one of them with (Pr ω > 1) > 0.95 and 10 sites with evidences of episodic selection. While annotated as hypothetical proteins, all sequences in this cluster contain two copies of a domain associated with drug/metabolite transport.…”

Phytochemical, Antimicrobial and Sensory Qualities of Herbal Tea Made from Sarcandra glabra and Drymis piperita

“…Proteins are the huge group of macromolecules and act as antibiotic and antimicrobial agents. Reference [18] explained that protein recycling could lead to production of smaller proteins important in plant defense activation and other regulatory functions. Glycosides and terpenes were not detected in the leaves of S. glabra and D. piperita.…”

Identification of the pXO1 plasmid in attenuatedBacillus anthracisvaccine strains

“…There was no point mutation, insertion, or deletion in the replication loci of the plasmid (InDel). Moreover, the ORFs of plasmid pXO1 in Pasteur II were annotated by using the Glimmer software [23][24] and compared with those in pXO1 of the Ames Ancestor strain (Fig. 3).…”