title: Ice recrystallization inhibition proteins (IRIPs) and freeze tolerance in the cryophilic Antarctic hair grass Deschampsia antarctica E. Desv.
abstract: Antarctic hair grass (Deschampsia antarctica E. Desv.), the only grass indigenous to Antarctica, has well-developed freezing tolerance, strongly induced by cold acclimation. Here, we show that in response to low temperatures, D. antarctica expresses potent recrystallization inhibition (RI) activity that, inhibits the growth of small ice crystals into potentially damaging large ones, is proteinaceous and localized to the apoplasm. A gene family from D. antarctica encoding putative homologs of an ice recrystallization inhibition protein (IRIP) has been isolated and characterized. IRIPs are apoplastically targeted proteins with two potential ice-binding motifs: 1-9 leucine-rich repeats (LRRs) and c. 16 'IRIP' repeats. IRIP genes appear to be confined to the grass subfamily Pooideae and their products, exhibit sequence similarity to phytosulphokine receptors and are predicted to adopt conformations with two ice-binding surfaces. D. antarctica IRIP (DaIRIP) transcript levels are greatly enhanced in leaf tissue following cold acclimation. Transgenic Arabidopsis thaliana expressing a DaIRIP has novel RI activity, and purified DaIRIP, when added back to extracts of leaves from non-acclimated D. antarctica, can reconstitute the activity found in acclimated plants. We propose that IRIP-mediated RI activity may contribute to the cryotolerance of D. antarctica, and thus to its unique ability to have colonized Antarctica.
authors.affiliation: Department of Primary Industries, Biosciences Research Division, Victorian AgriBiosciences Centre, 1 Park Drive, Bundoora, Vic. 3086, Australia. ulrik.john@dpi.vic.gov.au
authors.forename: Ulrik P
authors.initials: UP
authors.lastname: John
authors.forename: Renatam M
authors.initials: RM
authors.lastname: Polotnianka
authors.forename: Kailayapillai A
authors.initials: KA
authors.lastname: Sivakumaran
authors.forename: Orinda
authors.initials: O
authors.lastname: Chew
authors.forename: Leanne
authors.initials: L
authors.lastname: Mackin
authors.forename: Micheal J
authors.initials: MJ
authors.lastname: Kuiper
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Talbot
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Nugent
authors.forename: Julie
authors.initials: J
authors.lastname: Mautord
authors.forename: Gustavo E
authors.initials: GE
authors.lastname: Schrauf
authors.forename: German C
authors.initials: GC
authors.lastname: Spangenberg
mesh_terms: D000064:Acclimatization / Q000235:genetics; D000595:Amino Acid Sequence; D000864:Antarctic Regions; D021301:Antifreeze Proteins / Q000235:genetics* / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics; D003001:Cloning, Molecular; D003080:Cold Temperature; D018744:DNA, Plant / Q000235:genetics; D005615:Freezing; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007053:Ice; D008969:Molecular Sequence Data; D005810:Multigene Family; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics* / Q000502:physiology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology; D006109:Poaceae / Q000235:genetics* / Q000502:physiology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D021301:Antifreeze Proteins; D018744:DNA, Plant; D007053:Ice; D010940:Plant Proteins