Abstract
The gaseous plant hormone ethylene is a key signaling molecule regulating plant growth, development, and defense against pathogens. Octadecanoid-responsive arabidopsis 59 (ORA59) is an ethylene response factor (ERF) transcription factor and has been suggested to integrate ethylene and jasmonic acid signaling and regulate resistance to necrotrophic pathogens. Here we screened for ORA59 interactors using the yeast two-hybrid system to elucidate the molecular function of ORA59. This led to the identification of RELATED TO AP2.3 (RAP2.3), another ERF transcription factor belonging to the group VII ERF family. In binding assays, ORA59 and RAP2.3 interacted in the nucleus and showed ethylene-dependent nuclear localization. ORA59 played a positive role in ethylene-regulated responses, including the triple response, featured by short, thick hypocotyl and root, and exaggerated apical hook in dark-grown seedlings, and resistance to the necrotrophic pathogen Pectobacterium carotovorum, as shown by the increased and decreased ethylene sensitivity and disease resistance in ORA59-overexpressing (ORA59OE) and null mutant (ora59) plants, respectively. In genetic crosses, ORA59OE rap2.3 crossed lines lost ORA59-mediated positive effects and behaved like rap2.3 mutant. These results suggest that ORA59 physically interacts with RAP2.3 and that this interaction is important for the regulatory roles of ORA59 in ethylene responses.
Highlights
During evolution, plants have become equipped with defense mechanisms that enable them to survive against environmental stresses
To identify proteins that interact with Octadecanoid-responsive arabidopsis 59 (ORA59), we performed Y2H screening using a cDNA library prepared from ethephontreated Arabidopsis plants
Y2H screening led to the isolation of 12 proteins as potential ORA59 interactors (Table 1); among these, another ethylene response factor (ERF) member RAP2.3 was chosen for further analysis
Summary
Plants have become equipped with defense mechanisms that enable them to survive against environmental stresses. Salicylic acid (SA), jasmonic acid (JA), and ethylene are major hormones regulating the defense against pathogens (Glazebrook, 2005; Kwon et al, 2009; Pieterse et al, 2012). Whereas ethylene and JA signaling often interact synergistically, there is antagonism between SA and JA/ethylene (Penninckx et al, 1998; Thomma et al, 1998; Koornneef et al, 2008; Kim et al, 2013) This may be the outcome of evolution towards reducing the fitness cost, enabling plants to prioritize either the SA or JA/ethylene pathway depending on the lifestyle of invading pathogens
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