Eucalypt NADP-Dependent Isocitrate Dehydrogenase1
cDNA Cloning and Expression in Ectomycorrhizae
Vincent Boiffin2,
Michael Hodges,
Susana Gálvez,
Raffaella Balestrini,
Paola Bonfante,
Pierre Gadal, and
Francis Martin*
Equipe de Microbiologie Forestière, Institut National de la
Recherche Agronomique, Centre de Nancy, F-54280 Champenoux, France
(V.B., F.M.); Institut de Biotechnologie des Plantes, Centre National
de la Recherche Scientifique ERS 569, Bâtiment 630, Université Paris-Sud, F-91405 Orsay cédex, France (V.B.,
M.H., S.G., P.G.); and Dipartimento di Biologia Vegetale dell'
Università, Centro di Studio sulla Micologia del Terreno, del
Centro Nazionale de Ricerca, Viale Mattioli 25, I-10125 Torino, Italy
(R.B., P.B.)
NADP-dependent
isocitrate dehydrogenase (NADP-ICDH) activity is increased in roots of
Eucalyptus globulus subsp. bicostata ex
Maiden Kirkp. during colonization by the ectomycorrhizal fungus Pisolithus tinctorius Coker and Couch. To investigate
the regulation of the enzyme expression, a cDNA (EgIcdh)
encoding the NADP-ICDH was isolated from a cDNA library of E. globulus-P. tinctorius ectomycorrhizae. The
putative polypeptide sequence of EgIcdh showed a high
amino acid similarity with plant NADP-ICDHs. Because the deduced EgICDH
protein lacks an amino-terminal targeting sequence and shows highest
similarity to plant cytosolic ICDHs, it probably represents a
cytoplasmic isoform. RNA analysis showed that the steady-state level of
EgIcdh transcripts was enhanced nearly 2-fold in
ectomycorrhizal roots compared with nonmycorrhizal roots. Increased accumulation of NADP-ICDH transcripts occurred as early as 2 d after contact and likely led to the observed increased enzyme activity.
Indirect immunofluorescence microscopy indicated that NADP-ICDH was
preferentially accumulated in the epidermis and stele parenchyma of
nonmycorrhizal and ectomycorrhizal lateral roots. The putative role of
cytosolic NADP-ICDH in ectomycorrhizae is discussed.
1
This work was supported by research grants from
the Eureka-Eurosilva program ("Changes in Gene Expression during
Ectomycorrhiza Differentiation and Function") and the Groupement de
Recherche et d'Etude des Génomes. V.B. was supported by a
doctoral scholarship from the Ministère de l'Enseignement
Supérieur et de la Recherche.
2
Present address: Philipps Universität
Marburg, Fachbereich Biologie, Karl-von-Frisch Strasse, 35032 Marburg,
Germany.
*
Corresponding author; e-mail fmartin{at}nancy.inra.fr; fax
33-383-39-40-69.
Plant Physiol. (1998) 117: 939-948
Copyright Clearance Center: 0032-0889/98/117/0939/10
© 1998 American Society of Plant Physiologists
