Involvement of Polyamines in PAMP-triggered Immunity and Systemic Acquired Resistance (SAR). Extragenic Suppressors of Immune Hybrid Incompatibility

Abstract

The main topic of this Thesis is to investigate the contribution of polyamines to defense in Arabidopsis thaliana and the requirement of callose deposition for full expression of effector-triggered immunity in autoimmune hybrids. Due to its accumulation during pathogen infection, I mainly focused on the polyamine putrescine. The interaction between polyamines, reactive oxygen species (ROS) production and salicylic acid pathway activation is also studied in the context of PAMP-triggered immunity (PTI) (Chapter 1) and systemic acquired resistance (SAR) (Chapter 2). The data support a role for putrescine as a priming agent contributing to resistance against pathogens, which can lead to practical applications in the development of PPP (plant protection products). In Chapter 3, I report the involvement of glucan synthase-like 2 and 10 (GSL2 and GSL10), two of the twelve callose biosynthesis genes, in the temperature-dependent immune hybrid incompatibility between natural accessions of Arabidopsis thaliana from North Europe (Ler) and Central Asia (Kas-2), which constitutes a model for the study of effector-triggered immunity (ETI). This work supports that PTI and ETI are not two separate branches of defense, but support each other through mutual potentiation. Overall, we provide evidence for the involvement of polyamines in defense signaling and callose biosynthesis in the establishment of ETI.