Plants, as sessile organisms, have evolved complex systems to respond to changes in environmental conditions. Chitin is a Pathogen-Associated-Molecular Pattern (PAMP) that exists in the fungal cell walls, and can be recognized by plants and induce plant pattern-triggered immunity (PTI). Our previous studies showed that Arabidopsis Toxicos en Levadura 12 (ATL12) is highly induced in response to fungal infection and chitin treatment. We used the model organism Arabidopsis thaliana to characterize ATL12 and explore its role in fungal defense. Histochemical staining showed that pATL12-GUS was continually expressed in roots, leaves, stems, and flowers. Subcellular co-localization of the ATL12-GFP fusion protein with the plasma membrane-mcherry marker showed that ATL12 localizes to the plasma membrane. Mutants of atl12 are more susceptible to Golovinomyces cichoracearum infection, while overexpression of ATL12 increased plant resistance to the fungus. ATL12 is highly induced by chitin after two hours of treatment and ATL12 may act downstream of MAPK cascades. Additionally, 3,3'-diaminobenzidine (DAB) staining indicated that atl12 mutants generate less reactive oxygen species compared to wild-type Col-0 plants and RT-PCR indicated that ATL12-regulated ROS production may be linked to the expression of respiratory burst oxidase homolog protein D/F (AtRBOHD/F). Furthermore, we present evidence that ATL12 expression is upregulated after treatment with both salicylic acid and jasmonic acid. Taken together, these results suggest a role for ATL12 in crosstalk between hormonal, chitin-induced, and NADPH oxidase-mediated defense responses in Arabidopsis.
Keywords: Arabidopsis thaliana; Golovinomyces cichoracearum; NADPH oxidase; chitin; fungal defense; plant hormone.