Plant and Cell Physiology Advance Access originally published online on March 25, 2005
Plant and Cell Physiology 2005 46(6):884-891; doi:10.1093/pcp/pci093
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Molecular Characterization and Origin of Novel Bipartite Cold-regulated Ice Recrystallization Inhibition Proteins from Cereals
Université du Québec à Montréal, Département des Sciences biologiques, CP 8888, Succursale Centre-ville, Montréal, Québec H3C 3P8, Canada
2 Corresponding author: E-mail, sarhan.fathey{at}uqam.ca; Fax, +1-514-987-4647.
To understand the molecular basis of freezing tolerance in plants, several low temperature-responsive genes have been identified from wheat. Among these are two genes named TaIRI-1 and TaIRI-2 (Triticum aestivum ice recrystallization inhibition) that are up-regulated during cold acclimation in freezing-tolerant species. Phytohormones involved in pathogen defense pathways (jasmonic acid and ethylene) induce the expression of one of the two genes. The encoded proteins are novel in that they have a bipartite structure that has never been reported for antifreeze proteins. Their N-terminal part shows similarity with the leucine-rich repeat-containing regions present in the receptor domain of receptor-like protein kinases, and their C-terminus is homologous to the ice-binding domain of some antifreeze proteins. The recombinant TaIRI-1 protein inhibits the growth of ice crystals, confirming its function as an ice recrystallization inhibition protein. The TaIRI genes were found only in the species belonging to the Pooideae subfamily of cereals. Comparative genomic analysis suggested that molecular evolutionary events took place in the genome of freezing-tolerant cereals to give rise to these genes with putative novel functions. These apparent adaptive DNA rearrangement events could be part of the molecular mechanisms that ensure the survival of hardy cereals in the harsh freezing environments.
1 These authors contributed equally to this work.
The nucleotide sequences reported in this paper have been submitted to GenBank under accession numbers AY968588
(Received October 13, 2004; Accepted March 21, 2005)
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