Identification of an ice recrystallisation inhibition gene family in winter‐hardy wheat and its evolutionary relationship to other members of the Triticeae

Ice recrystallisation inhibition (IRI) proteins are important for plants that exist in cold environments. Six novel genes encoding IRI proteins were isolated from winter‐hardy wheat (Tricticum aestivum) cultivar (Mironovskaya808). Conserved domain analysis confirmed that all the predicted proteins contained the basic characteristics of IRI proteins, including leucine‐rich repeats (LRR) and IRI‐domains (NxVx1‐2G). In addition, these proteins possessed an N‐terminal signal peptide and some conserved cysteines. Despite the high conservation of the amino acid sequences, the characteristic regions still exist among these IRI‐domains of IRI sequences. All IRI sequences in this study are highly homologous with phytosulfokine receptors (PSR). Quantitative real‐time PCR (qPCR) analysis indicated that each member of the IRI gene family was induced after exposure to low temperature. Heterologous expression of IRI proteins enhanced freezing tolerance in host cells. A total of 28 IRI genes were isolated from Triticeae, and the evolutionary relationship of the IRI gene family in Triticeae and related species showed high interspecific specificity. The IRI genes from Aegilops, which is one of the progenitors of allohexaploid wheat, shared the closest relationship with those from Triticum. With high interspecific specificity in Triticeae, however, there was no specificity among different species of Triticum. Our results suggest that IRI genes have potential value to improve cold resistance of crops.