Auxin and coronatine signaling converge in guard cells.

RÍOS C; PIECKENSTAIN FL; GUDESBLAT GE

Rosario

Congreso; XXXIV Reunión Argentina de Fisiología Vegetal.; 2023

Certain hormones and bacterial compounds are known to inhibit ABA-induced stomatal closure, including auxins and coronatine, a bacterial toxin which is a structural analog of the jasmonate-isoleucine conjugate. Both are known to affect the activity of inward rectifying potassium channels as well as ROS synthesis in guard cells.In this work we seeked to understand the mechanism through which auxins and coronatine inhibit ABA-induced stomatal closure. Through the analysis of various Arabidopsis mutants affected in the signaling or transport of auxins and coronatine, we found that mutants insensitive to inhibition by coronatine of ABA-induced stomatal closure coi1-16, lecrkVI-2.1, mpk3, mpk6, npr1 and rbohd were also insensitive to the auxin IAA. On the other hand, tir1-1 and aux1 mutants, affected respectively in the perception and transport of auxins, display markedly reduced stomata reopening after three hours of incubation with the coronatine-producing bacterium Pseudomonas syringae pv. tomato DC3000 (which initially induces stomatal closure through PAMPs). In addition, natural variability was found for stomatal sensitivity to both coronatine and auxins. As far as it is known, the perception of both types of compounds occurs independently, so it is complex to explain the simultaneous insensitivity of auxin and coronatine in the aforementioned mutants.On the other hand, we have found that mutants affected in the silencing mechanism ago4, dcl2/3/4 and rdd also presented stomatal insensitivity to auxins, which may suggest that the regulation of sensitivity to this hormone could be partly mediated by transcriptional mechanisms.