Abstract

Background and Aims We have recently shown that an Arabidopsis thaliana double mutant of type III phosphatidylinositol-4-kinases (PI4Ks), pi4k beta 1 beta 2. constitutively accumulated a high level of salicylic acid (SA). By crossing this pi4k beta 1 beta 2 double mutant with mutants impaired in SA synthesis (such as sid2 impaired in isochorismate synthase) or transduction, we demonstrated that the high SA level was responsible for the dwarfism phenotype of the double mutant. I lere we aimed to distinguish between the SA-dependent and SA-independent effects triggered by the deficiency in PI4K beta 1 and PI4K beta 2.Methods To achieve this we used the sid2pi4k beta 1 beta 2 triple mutant. High-throughput analyses of phytohormones were performed on this mutant together with pi4k beta 1 beta 2 and sid2 mutants and wild-type plants. Responses to patho-gens. namely Hyaloperonospora arabidopsidis, Pseudomonas syringae and Botrytis cinerea, and also to the non-host fungus Blumeria graminis, were also determined. Callose accumulation was monitored in response to flagellin.Key Results We show here the prominent role of high SA levels in influencing the concentration of many other tested phytobormones. including abscisic acid and its derivatives, the aspartate-conjugated form of indole-3-acetic acid and some cytokinins such as cis-zeatin. We show that the increased resistance of pi4k beta 1 beta 2 plants to the host pathogens H. arabidopsidis. P. syringae pv. tomato DC3000 and Bothrytis cinerea is dependent on accumulation of high SA levels. In contrast, accumulation of callose in pi4k beta 1 beta 2 after flagellin treatment was independent of SA. Concerning the response to Blumeria graminis, both callose accumulation and fungal penetration were enhanced in the pi4k beta 1 beta 2 double mutant compared to wild-type plants. Both of these processes occurred in an SA-independent manner.Conclusions Our data extensively illustrate the influence of SA on other phytohormone levels. The sid2pi4k beta 1 beta 2 triple mutant revealed the role of PI4K beta 1/beta 2 per se, thus showing the importance of these enzymes in plant defence responses.

Keywords

pi4k beta 1 beta 2/PI4Ks; callose; salicylic acid; phytohormones; isochorismate synthase 1; biotic stress; pathogens; Arabidopsis thaliana

Published in

Annals of Botany
2020, Volume: 125, number: 5, pages: 775-784
Publisher: OXFORD UNIV PRESS

Associated SLU-program

SLU Plant Protection Network


UKÄ Subject classification

Botany


Publication identifier

DOI: https://doi.org/10.1093/aob/mcz112

Permanent link to this page (URI)

https://res.slu.se/id/publ/107223