Role of NPR1 and KYP in long-lasting induced resistance by β-aminobutyric acid

Abstract

Priming of defense increases the responsiveness of the plant immune system and can provide broad-spectrum protection against disease. Recent evidence suggests that priming of defense can be inherited epigenetically to following generations. However, the mechanisms of long-lasting defense priming within one generation remains poorly understood. Here, we have investigated the mechanistic basis of long-lasting induced resistance after treatment with β -aminobutyric acid (BABA), an agent that mimics biologically induced resistance phenomena. BABA-induced resistance (BABA-IR) is based on priming of salicylic acid (SA)-dependent and SA-independent defenses. BABA-IR could be detected up to 28 days after treatment of wild-type Arabidopsis. This long-lasting component of the induced resistance response requires the regulatory protein NPR1 and is associated with priming of SA-inducible genes. In contrast, NPR1-independent resistance by BABA was transient and had disappeared by 14 days after treatment. Chromatin immunoprecipitation (ChIP) assays revealed no increased acetylation of histone H3K9 at promoters regions of priming-responsive genes, indicating that this post-translational histone modification is not critical for long-term transcriptional priming. Interestingly, the kyp-6 mutant, which is affected in methyltransferase activity of H3K9, was blocked in long-lasting BABA-IR, indicating a critical requirement of this post-translational histone modification in long-lasting BABA-IR. Considering that KYP suppresses gene transcription through methylation of H3K9 and CpHpG DNA methylation, we propose that KYP enables long-term defense gene priming by silencing suppressor genes of SA/NPR1-dependent genes.

Long‐lasting β‐aminobutyric acid‐induced resistance protects tomato fruit against Botrytis cinerea

“…First, BABA induces resistance in numerous plant species against a range of biotic (Ton & Mauch‐Mani, ; Ton et al ., ; Luna et al ., ) and abiotic stresses (Jakab et al ., ). Secondly, BABA‐IR is long lasting, as described here and in other publications (Slaughter et al ., ; Worrall et al ., ; Luna et al ., , ). Thirdly, BABA is a priming‐inducing agent that provides a robust and consistent resistance response.…”

The role of DNA (de)methylation in immune responsiveness of Arabidopsis

“…Some priming responses are triggered by plant–microbe interactions, such as pathogen‐induced systemic acquired resistance (SAR; Durrant and Dong, ) or root microbe‐induced systemic resistance (Van Wees et al ., ), whereas others can be induced by application of specific chemicals, such as beta‐amino butyric acid (BABA; Luna et al ., 2014a). On a temporal scale, there are types of defence priming that are relatively short‐lived and disappear over days (Luna et al ., 2014b), whereas priming of SA‐ and JA‐dependent defences are long‐lasting (Worrall et al ., ; Luna et al ., 2014b), and can even be transmitted to the next generation, resulting in transgenerational acquired resistance (TAR; Luna et al ., ; Rasmann et al ., ; Slaughter et al ., ). The durable and heritable character of priming of SA‐dependent immunity have suggested involvement of epigenetic regulatory mechanisms, such as chromatin remodelling and DNA (de)methylation, which can account for long‐lasting changes in defence gene responsiveness (Jaskiewicz et al ., ; Pastor et al ., ; Conrath et al ., ).…”

Chitosan primes plant defence mechanisms againstBotrytis cinerea, including expression of Avr9/Cf-9 rapidly-elicited genes

“…Arabidopsis overexpression plants were transformed using A. tumefaciens GV3101 carrying plasmids with expression constructs using the flower dipping method (Clough and Bent, 1998). Selection of Arabidopsis transformants and homozygous lines selection were performed as described (Luna et al, 2014). Resistance was tested against B. cinerea as described before.…”