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

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

CLONING OF A WRKY TRANSCRIPTION ACTIVATOR INVOLVED IN THE COLD ACCLIMATION RESPONSE IN BARLEY

MARÈ C.*, MASTRANGELO A.M.*, RIZZA R.**, CATTIVELLI L.**

* Istituto Sperimentale per la Cerealicoltura, Sezione di Foggia, Foggia

** Istituto Sperimentale per la Cerealicoltura, Sezione di Fiorenzuola, Via S. Protaso 302, I-29017 Fiorenzuola d’Arda (PC)

l.cattivelli@iol.it

barley, cold acclimation, transcription factor

In the past years a number of cold-responsive (cor) genes expressed during acclimation to low temperature have been isolated and characterised in many crop species. Nevertheless only the CBF/DREB1 gene family of Arabidopsis thaliana codes for transcription activators which have been shown to control many cold and drought induced genes. CBF/DREB1 genes are themselves cold-regulated and their transcripts begin to accumulate within 15 min of transfer to low temperature, suggesting that differential screening techniques could be suitable for the isolation of new transcription factors.

By differential display RT-PCR technique we have isolated, from barley leaves, a cDNA induced after 3h of low temperature exposure. This transcript was characterised by an early and rapid expression in comparison with other known barley cor genes usually detectable only after 24 h of cold treatment. By using the differentially expressed cDNA the corresponding full length clone was recovered from a cDNA library. Sequence analysis of isolated cDNA revealed that this gene encodes for a 38kDa protein homologous to Avena fatua ABF2 a member of the large WRKY (pronounced “worky”) family of plant transcription factors. The barley gene, named corWRKY38, is characterised by the WRKY domain together with a novel zinc-finger-like motif (C-X_4-5-C-X_22-23-H-X₁-H) and a leucine zipper sequence. The accumulation of corWRKY38 transcripts was investigated by northern blot analysis. During hardening at +2°C the corWRKY38 expression is rapid and transient and achieves its highest level after 12 hours in the leaves and 5 hours in the roots. Since the corWRKY38 mRNAs disappear after 24h at +2°C, we have examined if a further temperature decrease promotes a new induction of corWRKY38. Barley plants were hardened at +2°C for one week, then submitted to –3°C or –8°C for 48 hours. The temperature steps down induced a rapid and stable accumulation of corWRKY38 mRNA providing that frozen temperatures still promote a molecular response. corWRKY38 mRNA accumulation is not affected by ABA or drought treatment.

The WRKY proteins, defined by the conserved amino acid sequence WRKYGOK, are involved in the regulation of varied physiological processes: pathogen defence, senescence and trichome development. This work provides the first evidence of involvement of WRKY transcription factors in cold-stress response.