A gene family in Arabidopsis thaliana with sequence similarity to NDR1 and HIN1

Abstract

The NDR1 gene of Arabidopsis thaliana is required for resistance to certain pathogens. Tobacco NDR1 and HIN1 share sequence similarity and are inducible in response to pathogen infection. In this study, 29 open reading frames were identified in Arabidopsis based on sequence similarity to NDR1 and HIN1. These N DR1 / H IN1 - l ike ( NHL) genes are similar in length and intron-exon structure, and share specific sequence motifs. The putative genes constitute a large gene family that potentially function in plant response to pathogen infection downstream of signal recognition. The cDNAs of two genes ( NHL1, NHL2) from chromosome 3 were isolated. Over-expression of NHL2 in transgenic Arabidopsis plants resulted in elevated levels of PR-1 expression and light-dependent ‘speck disease-like’ symptoms in the leaves. The NHL2 transgenic plants responded like wild type to infection by Pseudomonas syringae pv. tomato DC3000 ( Pst DC3000). Inoculation of Arabidopsis wild-type plants with Pst DC3000 did not change the expression level of NHL2, but altered expression of NHL3, a close relative of NHL2. The differential expression patterns in response to Pst DC3000 infection, together with induction of the PR-1 gene and ‘speck disease-like’ symptoms in NHL2 plants, suggest a potential role for various NDR1/ HIN1-like genes in plant-pathogen interactions.