Department of Biology, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
Department of Biomedical and Molecular Sciences, and School of Environmental Studies, Queen's University, Kingston, Ontario, K7L 3N6, Canada.
Plant Cell Environ. 2018 May;41(5):983-992. doi: 10.1111/pce.12889. Epub 2017 Feb 18.
Plants exposed to sub-zero temperatures face unique challenges that threaten their survival. The growth of ice crystals in the extracellular space can cause cellular dehydration, plasma membrane rupture and eventual cell death. Additionally, some pathogenic bacteria cause tissue damage by initiating ice crystal growth at high sub-zero temperatures through the use of ice-nucleating proteins (INPs), presumably to access nutrients from lysed cells. An annual species of brome grass, Brachypodium distachyon (Bd), produces an ice-binding protein (IBP) that shapes ice with a modest depression of the freezing point (~0.1 °C at 1 mg/mL), but high ice-recrystallization inhibition (IRI) activity, allowing ice crystals to remain small at near melting temperatures. This IBP, known as BdIRI, is unlike other characterized IBPs with a single ice-binding face, as mutational analysis indicates that BdIRI adsorbs to ice on two faces. BdIRI also dramatically attenuates the nucleation of ice by bacterial INPs (up to -2.26 °C). This 'anti-nucleating' activity is significantly higher than previously documented for any IBP.
植物在遭遇零度以下的温度时会面临独特的挑战，这些挑战威胁着它们的生存。细胞外空间中冰晶的生长会导致细胞脱水、质膜破裂，最终导致细胞死亡。此外，一些病原菌通过在高亚零度温度下利用冰核蛋白（INP）引发冰晶生长来造成组织损伤，推测是为了从裂解细胞中获取营养物质。一种一年生的雀麦属植物，Brachypodium distachyon（Bd），会产生一种与冰晶结合的蛋白（IBP），这种蛋白可以将冰晶塑造成适度的凹陷，从而降低冰点（在 1mg/mL 时约为 0.1°C），同时具有很高的冰晶再结晶抑制（IRI）活性，使得冰晶在接近融化温度时仍然保持较小的体积。这种 IBP 被称为 BdIRI，与其他具有单一冰晶结合面的已知 IBP 不同，因为突变分析表明 BdIRI 可以在两个面上吸附冰晶。BdIRI 还可以显著抑制细菌 INP 的成核作用（高达-2.26°C）。这种“抗成核”活性明显高于以前记录的任何 IBP。
