Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 5.04

Genomic approaches to dissect cold and drought Signal transductions in cereals

Crosatti C.*, Marè C.*, mazzucotelli E.**^,******, Govoni C.*, Mastrangelo A.**^,*******, Galiba G.***, Dubkovski J.****, Pecchioni N.*, Bassi R.*****, Cattivelli L.*

*) Experimental Institute for Cereal Research, 29017, Fiorenzuola d’Arda, Italy

**) Experimental Institute for Cereal Research, 71100, Foggia, Italy

***) Agricultural Institute of the Hungarian Academy of Sciences, Martonvásár, Hungary

****) Department of Agronomy & Range Science, University of California, Davis, CA 95616, USA

*****) University of Verona, Facolty of Science, 37134, Verona, Italy

******) Department of Biology, University of Ferrara, 44100 Ferrara, Italy

*******) Department Genetics and Microbiology, University of Milano, 20133 Milano, Italy

cold, drought, mutant, transcription factor, QTL

The molecular dissection of cold and drought stress response in cereal has revealed a complex situation, where the co-ordinated expression of a series of stress-related genes is associated with increased levels of resistance. According to their expression patterns the cereal stress related genes isolated in our lab can be classified as cold-induced, cold and drought-induced or cold drought and ABA-induced, suggesting the existence of different stress-related signal transduction pathways.

In the recent years we have followed three genomic strategies to identify components involved in the regulation of the stress response.

Identification of mutants with impaired stress related gene expression

We have found that the expression of several stress related genes induced by low temperature only is impaired in plants carrying albino or xantha mutations suggesting that a chloroplast factor is involved in the cold-dependent, but not in other stress-related signal transduction pathways.

Identification of cis-elements and cloning of stress induced transcription factors

Deletion and mutation analysis were used to identify a novel cold-responsive cis-element in the promoter of the cold induced genes cor14b. To prove the activity of this motif several chimeric cor14b-uidA constructs were produced and assayed by transient expression after biolistic particle bombardment into leaves of wild type and albino barley plants.

Since other known stress related transcription factors are themselves stress-regulated and their transcripts begin to accumulate during the early events of stress response, we used differential display RT-PCR and suppression subtractive library (developed using Clonthech PCR-select subtraction kit) to identify early stress related genes. Among about 15 different early induced stress-related sequence three shared a clear homology with MYB, AP2 and WRKY (pronounced “worky”) transcription factor gene families. They expression was equally promoted both by cold and drought stress. While stress induced MYB and AP2 sequences were already described in other species the involvement of a WRKY sequence in stress response represent a novel finding.

Mapping of QTL for cold-induced gene expression and co-segregation with candidate genes

We have shown by genetic analysis that the expression of the some cold-induced genes is positively correlated with the level of frost tolerance in barley and wheat. Studies made with chromosome substitution lines in wheat as well as with segregant populations in barley and in T. monococcum, showed that the expression of cor14b is controlled by the same genomic region where the QTL’s for frost resistance have been located. Current experiments aim to map all available stress related transcription factors in order to verify their association with frost resistance.

The results obtained from the approaches described above, led to the identification of several signal transduction components homologous to those found in arabidopsis as well as of novel features not described in other species.