Overexpression of the Apple MpNPR1 Gene Confers Increased Disease Resistance in Malus × domestica

Abstract

The NPR1 gene plays a pivotal role in systemic acquired resistance in plants. Its overexpression in Arabidopsis and rice results in increased disease resistance and elevated expression of pathogenesis-related (PR) genes. An NPR1 homolog, MpNPR1-1, was cloned from apple (Malus x domestica) and overexpressed in two important apple cultivars, Galaxy and M26. Apple leaf pieces were transformed with the MpNPR1 cDNA under the control of the inducible Pin2 or constitutive Cauliflower mosaic virus (CaMV)35S promoter using Agrobacterium tumefaciens. Overexpression of MpNPR1 mRNA was shown by reverse transcriptase-polymerase chain reaction. Activation of some PR genes (PR2, PR5, and PR8) was observed. Resistance to fire blight was evaluated in a growth chamber by inoculation of the shoot tips of our own rooted 30-cm-tall plants with virulent strain Ea273 of Erwinia amylovora. Transformed Galaxy lines overexpressing MpNPR1 had 32 to 40% of shoot length infected, compared with 80% in control Galaxy plants. Transformed M26 lines overexpressing MpNPR1 under the control of the CaMV35S promoter also showed a significant reduction of disease compared with control M26 plants. Some MpNPR-overexpressing Galaxy lines also exhibited increased resistance to two important fungal pathogens of apple, Venturia inaequalis and Gymnosporangium juniperi-virginianae. Selected transformed lines have been propagated for field trials for disease resistance and fruit quality.

Arabidopsis genes, AtNPR1, AtTGA2 and AtPR-5, confer partial resistance to soybean cyst nematode (Heterodera glycines) when overexpressed in transgenic soybean roots

“…Overexpression of AtNPR1 in wheat conferred resistance to fusarium head blight, caused by Fusarium graminearum. The apple MpNPR1 gene confers resistance to two fungal pathogens of apple, Venturia inaequalis and Gymnosporangium juniper-virginianae [106,107] complemented Arabidopsis npr1-1 mutants with soybean homologs GmNPR1-1 and NPR1-2, and PR-1 was induced in the transformed plants after infection with P. syringae and after treatment with the SAR inducer, 2,6-dichloroisonicotinic acid.…”

Molecular Cloning and Characterization of an Ortholog of NPR1 Gene from Dongguan Dajiao (Musa spp. ABB)

“…Homologs of the AtNPR1 gene have now been isolated from several plant species (Liu et al 2002;Zhu et al 2003;Chern et al 2005;Meur et al 2006;Malnoy et al 2007;Endah et al 2008), but functional analysis has been carried out primarily only in the model plant Arabidopsis and rice.…”

“…A disease resistance pathway similar to that of the Arabidopsis NPR1 (AtNPR1)-mediated signaling pathway was demonstrated in rice (Chern et al 2001). Overexpression of AtNPR1 in Arabidopsis, rice, tomato, wheat, and apple have been showed to enhance fungal and bacterial resistance (Cao et al 1998;Chern et al 2001;Lin et al 2004;Makandar et al 2006;Malnoy et al 2007). Thus, NPR1 represents an ideal target for engineering broad-spectrum pathogen resistance in agriculture and encourage the search for functional NPR1-like genes in other plant species.…”

An Insight into Transgenic Development Activities in Fruit Crops

“…Some transgenic plants also showed some resistance to Venturiainaequalis and Gymnosporangiumjuniperi-virginianae (Malnoy et al, 2007).…”