Several downy mildew resistance genes in Arabidopsis require signaling via a homologue of yeast SGT1

Abstract

A fast neutron mutant in Arabidopsis (Columbia) was identified that exhibits enhanced downy mildew (edm1) susceptibility to several Peronospora parasitica isolates, including the RPP7-diagnostic isolate Hiks1. The mutation was mapped to chr.4 and physically characterised as a 35kb deletion spanning seven genes. One of these genes restored wild-type resistance to all of the P. parasitica isolates. This gene (AtSGT1b) encodes a predicted protein that is orthologous to yeast SGT1, originally described as a key regulatory protein in centromere function and ubiquitin-mediated proteolysis. AtSGT1b contains three tatratrico-peptide repeats at the N terminus followed by a bipartite "CS" (CHORD containing Sgt) domain and an SGT specific (SGTS) domain at the carboxyl terminus. Altered expression of this gene is being investigated in Arabidopsis and Brassica olarecea to determine its potential use for crop improvement.

Keywords

• brassica
• downy mildew resistance
• defence signalling
• sgt1