AUTHOR=Jordá Lucía , Sopeña-Torres Sara , Escudero Viviana , Nuñez-Corcuera Beatriz , Delgado-Cerezo Magdalena , Torii Keiko U. , Molina Antonio 

TITLE=ERECTA and BAK1 Receptor Like Kinases Interact to Regulate Immune Responses in Arabidopsis

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00897

DOI=10.3389/fpls.2016.00897

ISSN=1664-462X

ABSTRACT=<p>ERECTA (ER) receptor-like kinase (RLK) regulates <italic>Arabidopsis thaliana</italic> organ growth, and inflorescence and stomatal development by interacting with the ERECTA-family genes (ERf) paralogs, ER-like 1 (ERL1) and ERL2, and the receptor-like protein (RLP) TOO MANY MOUTHS (TMM). ER also controls immune responses and resistance to pathogens such as the bacterium <italic>Pseudomonas syringae</italic> pv. <italic>tomato DC3000</italic> (<italic>Pto</italic>) and the necrotrophic fungus <italic>Plectosphaerella cucumerina BMM</italic> (<italic>PcBMM</italic>). We found that <italic>er</italic> null-mutant plants overexpressing an ER dominant-negative version lacking the cytoplasmic kinase domain (ERΔK) showed an enhanced susceptibility to <italic>PcBMM</italic>, suggesting that ERΔK associates and forms inactive complexes with additional RLKs/RLPs required for <italic>PcBMM</italic> resistance. Genetic analyses demonstrated that <italic>ER</italic> acts in a combinatorial specific manner with <italic>ERL1, ERL2</italic>, and <italic>TMM</italic> to control <italic>PcBMM</italic> resistance. Moreover, BAK1 (<underline>B</underline>RASSINOSTEROID INSENSITIVE 1-<underline>a</underline>ssociated <underline>k</underline>inase 1) RLK, which together with ERf/TMM regulates stomatal patterning and resistance to <italic>Pto</italic>, was also found to have an unequal contribution with ER in regulating immune responses and resistance to <italic>PcBMM</italic>. Co-immunoprecipitation experiments in <italic>Nicotiana benthamiana</italic> further demonstrated BAK1-ER protein interaction. The secreted epidermal pattern factor peptides (EPF1 and EPF2), which are perceived by ERf members to specify stomatal patterning, do not seem to regulate ER-mediated immunity to <italic>PcBMM</italic>, since their inducible overexpression in <italic>A. thaliana</italic> did not impact on <italic>PcBMM</italic> resistance. Our results indicate that the multiproteic receptorsome formed by ERf, TMM and BAK1 modulates <italic>A. thaliana</italic> resistance to <italic>PcBMM</italic>, and suggest that the cues underlying ERf/TMM/BAK1-mediated immune responses are distinct from those regulating stomatal pattering.</p>