M. Carneiro et F. Vilaine, DIFFERENTIAL EXPRESSION OF THE ROLA PLANT ONCOGENE AND ITS EFFECT ON TOBACCO DEVELOPMENT, Plant journal, 3(6), 1993, pp. 785-792
The rolA gene not only provokes the abnormal traits of wrinkled leaves
, shortened internodes, and deficient root growth in tobacco, but also
induction of roots in leaf disks in hormone-free medium. The rolA mRN
A is most abundant in the stem of transgenic tobacco, accumulating at
fivefold and 50-fold lower levels in the leaf and the root, respective
ly. Promoter deletion mutants were constructed and the rolA-induced ab
normal traits were exploited to identify promoter regulatory regions.
The removal of specific promoter domains provokes the appearance of ne
w patterns of rolA transcripts in leaves, stems and roots. These new p
atterns are correlated with the disappearance of specific abnormal tra
it, thereby identifying three functional domains. Domain A includes a
mosaic motif composed of a putative GT-2 binding site and DUENDE eleme
nts. This domain positively regulates rolA gene expression in the leaf
and negatively regulates it in the stem and root. Domains B and C, wh
ich contain sequences homologous to the OCS enhancer and to ASF-1 bind
ing sites, respectively, generally activate the rolA gene expression i
n all tissues. The possible function of these elements on the regulati
on of the rolA gene is discussed.