Plant Physiol, September 2001, Vol. 127, pp. 78-89
Srchi24, A Chitinase Homolog Lacking an Essential Glutamic Acid
Residue for Hydrolytic Activity, Is Induced during Nodule
Development on Sesbania rostrata1
Sofie
Goormachtig,2
Willem
Van de
Velde,2
Sam
Lievens,
Christa
Verplancke,
Sylvia
Herman,
Annick
De Keyser, and
Marcelle
Holsters*
Vakgroep Moleculaire Genetica, Departement Plantengenetica, Vlaams
Interuniversitair Instituut voor Biotechnologie, Universiteit Gent,
Karel Lodewijk Ledeganckstraat 35, B-9000 Gent, Belgium
The interaction between the tropical legume Sesbania
rostrata and the bacterium Azorhizobium
caulinodans results in the formation of nodules on both stem
and roots. Stem nodulation was used as a model system to isolate early
markers by differential display. One of them, Srchi24 is
a novel early nodulin whose transcript level increased already 4 h
after inoculation. This enhancement depended on Nod factor-producing
bacteria. Srchi24 transcript levels were induced also by
exogenous cytokinins. In situ hybridization and immunolocalization
experiments showed that Srchi24 transcripts and proteins
were present in the outermost cortical cell layers of the developing
nodules. Sequence analyses revealed that Srchi24 is similar to class
III chitinases, but lacks an important catalytic glutamate residue. A
fusion between a maltose-binding protein and Srchi24 had no detectable
hydrolytic activity. A function in nodulation is proposed for the
Srchi24 protein.
1
This work was supported by the Vlaams Instituut
voor de Bevordering van het Wetenschappelijk-Technologisch Onderzoek in
de Industrie (predoctoral fellowship to W.V.d.V.). S.G. is a
Postdoctoral Fellow of the Fund for Scientific Research (Flanders).
2
These authors contributed equally to this work.
*
Corresponding author; e-mail mahol{at}gengenp.rug.ac.be; fax
32-9-2645349.
© 2001 American Society of Plant Physiologists
