TABLE CONTENTS

Tomato Innate Immunity to Root-knot Nematodes
Kaloshian, I., K.K. Bhattarai, S. Mantelin & U. Bishnoi
Department of Nematology, University of California, Riverside, CA 92521, USA.
Responses of resistant (Mi-1/Mi-1) and susceptible (mi-1/mi-1) tomato (Solanum
lycopersicum) to root-knot nematode (Meloidogyne spp.) infection were monitored using
cDNA microarrays and the role of salicylic acid (SA) and jasmonic acid (JA) defense
signaling was evaluated during these interactions. Array analysis was used to compare
transcript profiles in compatible and incompatible interactions of tomato roots 24h after
nematode infection. The jai1 and def1 tomato mutant, altered in JA perception and signaling,
respectively, and tomato transgenic line NahG, altered in SA signaling were evaluated in the
presence or absence of the root-knot nematode resistance gene Mi-1. The array analysis
identified 1497 and 750 genes differentially regulated in the incompatible and compatible
interactions, respectively. Of the differentially regulated genes, 37% were specific to the
incompatible interactions. NahG affected neither Mi-1 resistance nor basal defenses to rootknot
nematodes. However, jai1 reduced tomato susceptibility to root-knot nematodes, while
not affecting Mi-1 resistance. In contrast, the def1 mutant did not affect root-knot nematode
susceptibility. These results indicate that JA-dependent signaling does not play a role in Mi-1-
mediated defense but an intact JA signaling pathway is required for tomato susceptibility to
root-knot nematodes. In addition, low levels of SA might be sufficient for basal and Mi-1
resistance to root-knot-nematodes.
Early Resistance Responses of Coffee (Coffea arabica) to Root-knot
Nematode (Meloidogyne spp.) Infection
Albuquerque, E.V.S., A-C. Lecouls, A-S. Petitot, M.F. Grossi de Sa & D. Fernandez
Résistance des Plantes aux Bioagresseurs, Institut de Recherche pour le Développement, Montpelier Cedex,
France
Root-knot nematodes (Meloidogyne sp.) are major pests damaging the cash crop coffee
culture (Coffea arabica) in Latin America. C. arabica varieties resistant to M. exigua or M.
incognita were identified and resistant coffee roots exhibited a typical hypersensitive
response (HR). To understand physiological and molecular mechanisms underlying coffee
resistance responses to Meloidogyne spp., we undertook a genomic approach based on the
construction of substractive (SSH) cDNA libraries. SSH libraries were generated from pools
of total RNA obtained from excised root tips 2 and 4 days after inoculation with M. exigua.
Functional annotation of the unigene set showed that 30% of the ESTs encoded putative
homologues of known resistance- and defence-related proteins. In addition, half of the ESTs
unigene set represented novel coffee genes and 35% of the annoted ESTs did not share
significant similarity to plant protein database entries. Real-time quantitative RT-PCR
expression analyses of 115 genes from several functional categories were monitored during
M. exigua infection time-courses of resistant and susceptible coffee varieties. A higher
number of genes exhibited expression changes in the susceptible variety than in the resistant
variety (60 and 40 %, respectively) and a significant number were activated in the susceptible
variety (37%). In HR-exhibiting plants, only 17% of genes were up-regulated, displaying
transient regulation over 5-days time course experiments. A comparative study of the coffee
gene regulation during resistance to M. incognita is currently ongoing to select for common
Meloidogyne resistance reponses-candidate genes. Functional analysis of candidate genes in
Agrobacterium rhizogenes-transformed roots assays will reveal new insights into plant
resistance responses to root-knot nematodes.
5 th International Congress of Nematology, 2008 128