Disease cycle of potato late blight - MSpace at the University of ...

Once the host recognizes a pathogen via pathogen-associated molecular patterns
(PAMPs), also called MAMPs, microbe-associated molecular patterns, it activates
defense responses (Göhre and Robatzek 2008). PAMPs are essential for microbial
survival or processes and cannot be lost without significant consequences (Gomez-
Gomez and Boller 2002; Nurnberger and Brunner 2002). Numerous PAMPs have been
isolated from bacteria, oomycetes, and fungi. In fungi, β-1,3-glucan, chitin, and ergosterol
have been identified (Nurnberger et al. 2004; Altenbach and Robatzek 2007). The
Phytophthora PAMP Pep-13 (Brunner et al. 2002), induces oxidative burst, the
accumulation of salicylic acid (SA), jasmonic acid (JA), hydrogen peroxide, defense gene
expression and hypersensitive response (HR) in potato (Halim et al. 2004). It has been
shown that SA (Ellis and Amrhein 1971; Coquoz et al. 1998), JA, jasmonic methyl ester
(Cohen et al. 1991), and nitric oxide (NO) radicals (Noritake et al. 1996) can induce local
and systemic protection against P. infestans.
During infection, pattern recognition receptors (PRRs) in the plasma membrane
recognize PAMPs and trigger defense responses. They are highly sensitive and specific
recognition receptors for pathogen patterns. PRRs stimulate signaling cascades involving
Ca 2+ fluxes and mitogen activated protein kinases (MAPKs), leading to defense reactions.
Therefore, PAMP-Triggered Immunity (PTI), basal resistance or innate immunity is
activated, stimulating a transient immune response, which is not associated with visible
symptoms (Göhre and Robatzek 2008; Métraux et al. 2009). Typical defense responses
in PTI include, stomata closure (Melotto et al. 2006), thickening of the wall by formation
of papilla, lignin or callose (Keshavarzi et al. 2004), oxidative burst, activation of
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