Disease resistance to fungal diseases

Background on Resistance (R) genes and avirulence (Avr) genes (Hammond-Kosack & Jones 1997)

R genes are found in the plant, while corresponding Avr gene is in the pathogen

Presumed roles of R genes:

1. help plants detect pathogenic Avr gene products
2. initiate signal transduction pathways that will help defend against the pathogen
3. "have the capacity to evolve new R gene specificities rapidly"

If the R gene or corresponding pathogenic Avr gene are not present or altered, then plant is infected with the disease

The R protein recognizes the Avr gene product (ligand), activating a signal transduction cascade that initiates the defense against the pathogen. Thus, the R gene is turned on in healthy plants. R proteins must be able to evolve quickly in order to target new pathogens specifically. The evolution of the Avr genes directly impacts the evolution of the related R gene (coevolution).

Explanation of Chitin Signaling and Fungal Invasion Response -plants can recognize “surface-derived molecules” that elicit a general immune response (this is in addition to R gene-mediated pathways) – pathogen-associated or microbe-associated molecular patterns (PAMPs/MAMPs) -PAMPs are important for microbial invasion of a host cell -glucans, chitins, and proteins derived from fungal cell walls serve as elictors, or “pathogen derived molecules” Montesano et al 2003 -during fungal infection, chitinases in the infected cell degrade the chitin on the cell wall of the invading fungus -the remaining chitin fragments then also serve as elicitors that provoke necessary “defense response genes” -LysM RLKs (LsyM domain-containing receptor-like kinases): relatively large plant-specific protein family that researchers may suggest play a significant role in detecting fungal chitin

3 Common Blueberry Fruit Rots: ([ohioline.osu.edu/hyg-fact/3000/pdf/3213.pdf OSU])

1. Alternaria - postharvest rot; most common

Caused by Alternaria tenuissima

1. Anthracnose - serious pre- and postharvest disease

Caused by Colletotrichum acutatum (Yoshida et al. 2007)

1. Botrytis - normally minor, but can be severe

Caused by Botrytis cinerea

Things to Look Up:

abscisic acid?

KEGG Pathway - environmental information processing - signal transduction - plant hormone transduction

(look at dormancy)