The F-box protein MAX2 contributes to resistance to bacterial phytopathogens in Arabidopsis thaliana

Abstract

The F-box protein MORE AXILLARY GROWTH2 (MAX2) has previously been characterized for its role in plant development. MAX2 appears essential for the perception of the newly characterized phytohormone strigolactone, a negative regulator of polar auxin transport in Arabidopsis. Results: A reverse genetic screen for F-box protein mutants altered in their stress responses identified MAX2 as a component of plant defense. Here we show that MAX2 contributes to plant resistance against pathogenic bacteria. Interestingly, mutant plants showed increased susceptibility to the bacterial necrotroph as well as to the hemi-biotroph but not to the fungal necrotroph mutant phenotype was associated with constitutively increased stomatal conductance and decreased tolerance to apoplastic ROS but also with alterations in hormonal balance. Conclusions: Our results suggest that MAX2 previously characterized for its role in regulation of polar auxin transport in Arabidopsis, and thus plant development also significantly influences plant disease resistance. We conclude that the increased susceptibility to and is due to increased stomatal conductance in mutants promoting pathogen entry into the plant apoplast. Additional factors contributing to pathogen susceptibility in plants include decreased tolerance to pathogen-triggered apoplastic ROS and alterations in hormonal signaling.