The present invention relates to a nucleic acid molecule which encodes a
protein with the function of a plant Mg chelatase subunit CHLD or an
active fragment thereof; a protein which has the function of a plant Mg
chelatase subunit CHLD or an active fragment thereof, preferably a
recombinant protein; a method of determining the interaction of plant Mg
chelatase subunits, in which a host cell is transformed with a DNA
sequence as claimed in one or more of claims 1 to 3 and at least with one
DNA sequence encoding a further subunit of Mg chelatase in such a manner
that the interaction of the Mg chelatase gene products leads to a directly
or indirectly, qualitatively or quantitatively measurable signal,
preferably by activating a marker gene, and transgenic plants, transgenic
plant cells, transgenic plant organs, transgenic plant seeds, transgenic
propagation material comprising an abovementioned nucleic acid molecule.
