cgMT1, a metallothionein-like gene from the actinorhizal tree Casuarina glauca, is induced by wounding, oxidative stress and pathogen.

OBERTELLO, M; WALL, LG; LAPLAZE, L; GHERBI, H; AUGUY, F; BOGUSZ, D; FRANCHE, C

Åarhus, Dinamarca

Conferencia; 7th European Nitrogen Fixation Conference.; 2006

Our laboratory isolated and characterized from a cDNA library of young actinorhizal nodules of Casuarina glauca, a metallothionein-like cDNA named cgMT1. Metallothioneins (MT) are a group of low-molecular weight, cystein rich molecules that bind heavy metals. In plants, MT-like genes have been found in a wide variety of species, but their functions remain poorly understood. CgMT1 is a class I type 1 MT which encodes a 71-aminoacid polypeptide and the corresponding gene belongs to a small family. CgMT1 was found highly transcribed in roots and nodules, and in situ hybridization experiments demonstrated that the transcripts were located in the pericycle and in the infected nitrogen-fixing cells of the nodules. To further characterize cgMT1, a 1.2 kb fragment corresponding to the promoter was fused to the ß-glucuronidase reporter gene. When introduced into Arabidopsis thaliana, PcgMT1-gus was found to be highly expressed in roots. In the aerial part of the plants, reporter gene activity was low and restricted to the leaf and stem vascular systems. Wounding, hydrogen peroxyde, methyl viologen and the pathogen Xanthomonas campestris induced the reporter gene expression whereas heavy metals treatments had no notable effect. Transgenic Arabidopsis plants overexpressing the cgMT1 coding sequence under the control of the 35S promoter were found more susceptible to Xanthomonas than the untransformed plants. These data suggest that cgMT1 could participate in defense against intracellular oxidants.