Plant Defense Response

Plants are light-driven factories that supply organic carbon to our ecosystem. Therefore, they are exploited by a plethora of parasites, including microorganisms like fungi, bacteria and oomycetes. To cope with these enemies, plants possess an efficient defense system that recognizes non-self molecules or signals from their own injured cells. These recognition events lead to the synthesis of defense hormones, which act as central players in triggering and coordinating the plant defense responses (Pieterse et al., 2012).

The two major defense hormones are salicylic acid (SA) and jasmonoyl-isoleucine (JA-Ile). Their effects are modulated by other plant hormones like e.g. ethylene and abscisic acid. Though being a simplified concept, it is generally recognized that defense responses mediated by the phytohormone SA are effective against biotrophic pathogens (pathogens that exploit resources from living cells), whereas JA-Ile and ethylene act as crucial signalling molecules that induce responses against necrotrophs (pathogens that kill cells). In Arabidopsis thaliana, SA represses the JA/ET pathway (SA-JA/ET cross-talk), resulting in increased susceptibility of plants which are infected by biotrophs against subsequent attack by necrotrophs (Thyler et al., 2012).

TGA transcription factors play important roles in both, the SA and the JA/ET defense responses. We have obtained evidence that the TGA-interacting glutaredoxin ROXY19 is important for the SA-JA/ET cross-talk. One of our aims is to identify which protein is regulated by ROXY19 in this important process.