Dr. Norberto D. Iusem
Dr. Magdalena Rossi
Lic. Gustavo Gudesblat
Lic. Andrés Sambade
Cloning and molecular characterization of ABA-inducible genes in higher plants.
Molecular Physiology and Biology Laboratory
Department of Biology
School of Exact and Natural Sciences
University of Buenos Aires
1428 Ciudad Universitaria
Buenos Aires, Argentina
Summary of research projects
In order to study the mechanisms of induction of ABA-target genes involved in water stress responses and fruit ripening, we isolated a tomato (Lycopersicon esculentum) cDNA cloned named Asr1 (for abscisic, stress and ripenung). From a tomato genomic library and by using Asr1 as a probe, a genomic clone showing a 73% homology to Asr1 was obtained and named Asr2. Recently, data from the mapping of the Asr family on the RFLP map of the tomato genome allowed us to map these genes on chromosome 4. The whole nucleotide sequence of Asr2 showed consensus upstream regulatory elements. To assess that these regulatory sequences are functional in vivo as far as gene expression is concerned, we fused them upstream of the ß-glucuronidase (GUS) reporter gene. The resulting construct was used to transiently tansform papaya tissues, revealing promoter capabilities of such sequences (work done in collaboraton with Dr. Luis Herrera-Estrella, CINVESTAV, Mexico). In recent studies, by using the same construct to achieve stable transformation of papaya, potato and tobacco plants, we demonstrated that Asr2 promoter is responsive to ABA in transgenic tobacco and papaya but not in transgenic potato.
In addition, we are attempting to elucidate the biological function of the proteins encoded by the Asr genes by examining the phenotype displayed by transgenic tomato plants carrying the Asr1 gene in either the sense or the antisense orientation (work done in collaboration with Dr. Andrew Thompson, Horticulture Research Intl., UK and Dr. Don Grierson, University of Notthingham, UK).
We are currently considering the feasibility of manipulating the expression of genes relevant to agriculture under novel inducible promoters like that from Asr2. This would be particularly interesting in situations where a generalized expression driven by classical constitutive promoters is not desirable.