TABLE CONTENTS

Identifying Members of Mi-1-mediated Signaling Pathway using Virusinduced
Gene Silencing
Kaloshian, I.
Department of Nematology, University of California, Riverside, CA 92521, USA
The tomato Mi-1 gene encodes a protein with nucleotide-binding and leucine-rich repeat
motifs and mediates resistance to three root-knot nematodes (Meloidogyne arenaria, M.
incognita, M. javanica), potato aphids (Macrosyphum euphobiae) and whiteflies (Bemisia
tabaci). Mi-1-mediated resistance is characterized, in part, by the hypersensitive response
(HR), a form of programmed cell death. Using virus-induced gene silencing (VIGS) we have
functionally assessed the role of many genes during Mi-1-mediated defense in both Nicotiana
benthamiana and tomato. In N. benthamiana, a large-scale VIGS screen was performed by
targeting homologs of tobacco genes induced following TMV infection or treatment with
plant defense chemical elicitors. The silenced plants were then assayed by transient
expression of a constitutively active form of Mi-1, known as Mi-DS4, and phenotyped for
attenuation of MiDS4-mediated cell death. In tomato, candidate genes involved in plant
defense or Mi-1-mediated defense were silenced, and resulting lines assayed for attenuation
of Mi-1-mediated aphid or nematode resistance. From these VIGS screens, several genes that
play a role in Mi-1-mediated defense have been identified. Both novel genes and those
previously associated with plant defense against other plant pathogens were isolated.
5 th International Congress of Nematology, 2008 178