Systemic Acquired Resistance

TLDR

Systemic acquired resistance (SAR) is an enhanced, primed defense response that develops in plants after infection with necrotizing pathogens, enabling faster and stronger reactions to subsequent attacks and exemplifying plant memory, a concept studied since the early 20th century with major advances in the past sixteen years. This review synthesizes current knowledge of the molecular, biochemical, and physiological mechanisms underlying SAR. It examines the pathways that prime plants for improved defense after prior pathogen exposure.

Abstract

Upon infection with necrotizing pathogens many plants develop an enhanced resistance to further pathogen attack also in the uninoculated organs. This type of enhanced resistance is referred to as systemic acquired resistance (SAR). In the SAR state, plants are primed (sensitized) to more quickly and more effectively activate defense responses the second time they encounter pathogen attack. Since SAR depends on the ability to access past experience, acquired disease resistance is a paradigm for the existence of a form of "plant memory". Although the phenomenon has been known since the beginning of the 20th century, major progress in the understanding of SAR was made over the past sixteen years. This review covers the current knowledge of molecular, biochemical and physiological mechanisms that are associated with SAR.