Molecular Cloning and Functional Analysis of the NPR1 Homolog in Kiwifruit (Actinidia eriantha)

Abstract

Kiwifruit bacterial canker, caused by the bacterial pathogen Pseudomonas syringae pv. actinidiae (Psa), is a destructive disease in the kiwifruit industry globally. Consequently, understanding the mechanism of defense against pathogens in kiwifruit could facilitate the development of effective novel protection strategies. The Non-expressor of Pathogenesis-Related genes 1 (NPR1) is a critical component of the salicylic acid (SA)-dependent signaling pathway. Here, a novel kiwifruit NPR1-like gene, designated AeNPR1a, was isolated by using PCR and rapid amplification of cDNA ends techniques. The full-length cDNA consisted of 1952 base pairs with a 1,746-bp open-reading frame encoding a 582 amino acid protein. Homology analysis showed that the AeNPR1a protein is significantly similar to the VvNPR1 of grape. A 2.0 Kb 5′-flanking region of AeNPR1a was isolated, and sequence identification revealed the presence of several putative cis-regulatory elements, including basic elements, defense and stress response elements, and binding sites for WRKY transcription factors. Real-time quantitative PCR results demonstrated that AeNPR1a had different expression patterns in various tissues, and its transcription could be induced by phytohormone treatment and Psa inoculation. The yeast twohybrid assay revealed that AeNPR1a interacts with AeTGA2. Constitutive expression of AeNPR1a induced the expression of pathogenesis-related gene in transgenic tobacco plants and enhanced tolerance to bacterial pathogens. In addition, AeNPR1a expression could restore basal resistance to Pseudomonas syringae pv. tomato DC3000 (Pst) in Arabidopsis npr1-1 mutant. Our data suggest that AeNPR1a gene is likely to play a pivotal role in defense responses in kiwifruit.

Mitigation of Emergent Bacterial Pathogens Using Pseudomonas syringae pv. actinidiae as a Case Study—From Orchard to Gene and Everything in Between

“…Treatment of Psa-infected plants with ASM also resulted in the upregulation of PR1, PR2, PR5, and PR8 [134,152,155], supporting the important role of the SA pathway in the regulation of resistance gene-mediated signaling [154]. In addition, NPR1, a key component of the SA-dependent signaling pathway, was overexpressed in tolerant and susceptible genotypes shortly following infection with Psa [89,143,156]. Constitutive expression of this gene in transgenic tobacco plants induced the expression of PR genes and promoted tolerance against bacterial infection, restoring basal tolerance against P. syringae pv.…”

Genomic Variation and Host Interaction among Pseudomonas syringae pv. actinidiae Strains in Actinidia chinensis ‘Hongyang’

“…This pathway was significantly suppressed in Psa -inoculated ‘Hongyang’ ( Table 2 ). Although Psa biovar 3 is normally pathogenic to Actinidia species, some genotypes, such as A. eriantha and A. latifolia , are considerably resistant to Psa [ 20 , 37 , 38 ]. Similar resistance was observed in A. eriantha cv.…”

Defence‐related pathways, phytohormones and primary metabolism are key players in kiwifruit plant tolerance to Pseudomonas syringae pv. actinidiae

“…Several studies aiming at understanding the crosstalk between Psa and Actinidia spp. have demonstrated that the expression of numerous plant genes encoding different defence‐related pathways is induced in the first hours after infection, including (i) pathogen recognition, for example, FLS2, PBL9, pto3 ; (ii) PTI and ETI, for example, Pti1, Pti4, CERK1 ; (iii) disease resistance, for example, EDM2, RPS2, RIN4 ; (iv) general plant defences, for example, PR‐proteins, EIN2, MLP28, TLP1 ; (v) ROS scavenging, for example, APX, CAT, CXXS1, RBOHA and SOD and (vi) regulation, for example, WRKY25, MPK6, PDR1 (Beatrice et al, 2016; Cellini et al, 2014; Li et al, 2020; Nunes da Silva et al, 2020; Song et al, 2019; Sun et al, 2020; Tahir et al, 2019; T. Wang et al 2018; Z. Wang et al, 2017; Wurms et al, 2017a). In the present work, Psa endophytic population was significantly higher in A. chinensis var.…”