Vitis vinifera VvNPR1.1 is the functional ortholog of AtNPR1 and its overexpression in grapevine triggers constitutive activation of PR genes and enhanced resistance to powdery mildew

Abstract

Studying grapevine (Vitis vinifera) innate defense mechanisms is a prerequisite to the development of new protection strategies, based on the stimulation of plant signaling pathways to trigger pathogen resistance. Two transcriptional coactivators (VvNPR1.1 and VvNPR1.2) with similarity to Arabidopsis thaliana NPR1 (Non-Expressor of PR genes 1), a well-characterized and key signaling element of the salicylic acid (SA) pathway, were recently isolated in Vitis vinifera. In this study, functional characterization of VvNPR1.1 and VvNPR1.2, including complementation of the Arabidopsis npr1 mutant, revealed that VvNPR1.1 is a functional ortholog of AtNPR1, whereas VvNPR1.2 likely has a different function. Ectopic overexpression of VvNPR1.1 in the Arabidopsis npr1-2 mutant restored plant growth at a high SA concentration, Pathogenesis Related 1 (PR1) gene expression after treatment with SA or bacterial inoculation, and resistance to virulent Pseudomonas syringae pv. maculicola bacteria. Moreover, stable overexpression of VvNPR1.1-GFP in V. vinifera resulted in constitutive nuclear localization of the fusion protein and enhanced PR gene expression in uninfected plants. Furthermore, grapevine plants overexpressing VvNPR1.1-GFP exhibited an enhanced resistance to powdery mildew infection. This work highlights the importance of the conserved SA/NPR1 signaling pathway for resistance to biotrophic pathogens in V. vinifera.

Neofusicoccum parvum Colonization of the Grapevine Woody Stem Triggers Asynchronous Host Responses at the Site of Infection and in the Leaves

“…In Arabidopsis , the onset of SAR is dependent on the transcription cofactor NPR1 (Nonexpressor of PR genes) and its associated TFs, such as TGAs (Fu and Dong, 2013). In our study, VvNPR1.1 ( VIT_11s0016g01990 ; Le Henanff et al, 2011) was up-regulated at 24 hpi in stems and at both 24 hpi and 2 wpi in leaves, suggesting that the distal response could be associated with activation of SAR, which started at 24 hpi and was fully established by 2 wpi. Further experiments are necessary to establish if broad-spectrum defenses are activated in distal tissues in response to N. parvum infection.…”

“…For example, the MYC2 gene ( VIT_02s0012g01320 ), a regulator of jasmonic acid signaling was found up-regulated exclusively in stems. We also observed the specific up-regulation of the putative negative regulator of systemic acquired resistance (SAR) VvNPR1.2 ( VIT_10s0042g01250 ) in leaves starting at 24 hpi until 6 wpi (Bergeault et al, 2010; Le Henanff et al, 2011). …”

The NPR1 ortholog PhaNPR1 is required for the induction of PhaPR1 in Phalaenopsis aphrodite

“…(B) Alignment of PhaNPR1 (underlined) with NPR1 homologs whose localizations have been determined. AtNPR3, AtNPR4 from Arabidopsis (Liu et al, 2005; Zhang et al, 2006), MhNPR1 from Malus hupehensis (Zhang et al, 2011), GmNPR1-1 from Glycine max (Sandhu et al, 2009), VvNPR1.1 from grapevine (Le Henanff et al, 2011), and NtNPR1 from tobacco (Maier et al, 2010), were localized to the nucleus, while AtNPR1 from Arabidopsis , TcNPR1 from Theobroma cacao (Shi et al, 2010), and OsNPR1/NH1 from rice were localized to the cytoplasm without reductants. The BTB/POZ and ANK domains, and the C-terminal nuclear localization signal (NLS) are indicated with a solid-lined box, underline, and dashed-lined box, respectively.…”

“…However, a negative role in regulation of PR genes was later proposed (Zhang et al, 2006). Moreover, VvNPR1.2, which was classified in the NPR3 subgroup (Figure 2) in grape, could not compliment the function of Arabidopsis NPR1 (Le Henanff et al, 2011), suggesting a different function for proteins in the NPR3 subgroup. However, two closely related proteins of VvNPR1.2, GmNPR1-1 and GmNPR1-2 (Figure 2) from soybean, complimented the Arabidopsis npr1-1 mutant and were considered as functional orthologs of Arabidopsis NPR1 (Sandhu et al, 2009).…”

“…In contrast, overexpression of NPR1 protein enhances broad-spectrum disease resistance in Arabidopsis, rice and wheat, suggesting that the NPR1-mediated defense mechanism is evolutionary conserved across a wide range of species (Cao et al, 1998; Chern et al, 2001; Makandar et al, 2006). In addition, NPR1 homologs from rice ( OsNPR1 / NH1 ), Theobroma cacao ( TcNPR1 ), or Vitis vinifera ( VvNPR1.1 ) were able to complement an npr1 mutation in Arabidopsis (Le Henanff et al, 2011; Shi et al, 2010). However, in contrast to NPR1 overexpression in Arabidopsis , the overexpression of OsNPR1/NH1 in rice spontaneously activated resistant genes and resulted in a lesion-mimic phenotype (Chern et al, 2005).…”