Mutation of a Gene in the Fungus Leptosphaeria maculans Allows Increased Frequency of Penetration of Stomatal Apertures of Arabidopsis thaliana

Abstract

Leptosphaeria maculans, a pathogen of Brassica napus, is unable to invade most wild-type accessions of Arabidopsis thaliana, although several mutants are susceptible. The infection pathway of L. maculans via a non-invasive inoculation method on A. thaliana lms1 (undefined), pmr4-1 (defective in callose deposition), and pen1-1 and pen2-1 (defective in non-host responses to several pathogens) mutants is described. On wild types Col-0 and Ler-0, hyphae are generally arrested at stomatal apertures. A T-DNA insertional mutant of L. maculans (A22) that penetrates stomatal apertures of Col-0 and Ler-0 five to seven times more often than the wild-type isolate is described. The higher penetration frequency of isolate A22 is associated with an increased hypersensitive response, which includes callose deposition. Complementation analysis showed that the phenotype of this isolate is due to T-DNA insertion in an intronless gene denoted as ipa (increased penetration on Arabidopsis). This gene is predicted to encode a protein of 702 amino acids with best matches to hypothetical proteins in other filamentous ascomycetes. The ipa gene is expressed in the wild-type isolate at low levels in culture and during infection of A. thaliana and B. napus.

Immobilized Subpopulations of Leaf Epidermal Mitochondria Mediate PENETRATION2-Dependent Pathogen Entry Control in Arabidopsis

“…This begs the question why PEN2 associates with peroxisome membranes at all. In this context, it is important to note that PEN2 mutations affect a remarkably broad spectrum of interactions with various microbes, including other fungal pathogens such as Plectosphaerella cucumerina (Sanchez-Vallet et al, 2010), Magnaporthe oryzae (Maeda et al, 2009), Leptosphaeria maculans (Elliott et al, 2008), and Colletotrichum species (Hiruma et al, 2010), oomycetes (e.g., Phytophthora brassicae; Schlaeppi et al, 2010), and a growth-promoting endophytic fungus (Piriformospora indica; Jacobs et al, 2011). An important question for the future will be whether or not the peroxisomal PEN2 protein subpool is critical for resistance against these pathogens and what the subcellular behavior of peroxisomes, mitochondria, and the PEN2 protein is like in these interactions.…”

The cross-pathway control system regulates production of the secondary metabolite toxin, sirodesmin PL, in the ascomycete, Leptosphaeria maculans

“…To generate sirodesmin-deficient mutants of L. maculans , wild type isolate IBCN 18 was transformed with plasmid pGTII, which contains T-DNA with a selectable marker (hygromycin-resistance) thus generating random insertional mutants [15]. Two hundred such mutants were then screened using a bioassay that exploits the antibacterial properties of sirodesmin PL [2].…”

“…Two hundred T-DNA insertional mutants generated by transforming wild type Leptosphaeria maculans isolate IBCN 18 with plasmid pGTII [15] were screened for ones with low levels of sirodesmin PL [2]. Six-day-old cultures grown on 10% Campbell's V8 juice agar grown at 22°C with a 12 h/12 h light/dark cycle were overlaid with a suspension of Bacillus subtilis (NCTC 8236) in Luria Broth agar.…”

Fight to the death: Arabidopsis thaliana defense response to fungal necrotrophic pathogens

“…1a). It is aimed at separating the fungus from healthy tissues to prevent further fungal expansion (Elliott et al 2008;Meyer et al 2009). An enzyme that seems to be responsible for Brassica napus tolerance to A. brassicae is cinnamyl alcohol dehydrogenase (CAD).…”