Low temperature is a major abiotic stress that seriously limits mangrove productivity and distribution. Kandelia obovata is the most cold-resistance specie in mangrove plants, but little is known about the molecular mechanism underlying its resistance to cold. Osmotin is a key protein associated with abiotic and biotic stress response in plants but no information about this gene in K. obovata was reported. In this study, a cDNA sequence encoding osmotin, KoOsmotin (GenBank accession no. KP267758), was cloned from mangrove plant K. obovata. The KoOsmotin protein was composed of 221 amino acids and showed a calculated molecular mass of 24.11 kDa with pI 4.92. The KoOsmotin contained sixteen cysteine residues and an N-terminal signal peptide, which were common signatures to most osmotins and pathogenesis-related 5 proteins. The three-dimensional (3D) model of KoOsmotin, contained one α-helix and eleven β-strands, was formed by three characteristic domains. Database comparisons of the KoOsmotin showed the closest identity (55.75%) with the osmotin 34 from Theobroma cacao. The phylogenetic tree also revealed that the KoOsmotin was clustered in the branch of osmotin/OLP (osmotin-like protien). The KoOsmotin protein was proved to be localized to both the plasma membrane and cytoplasm by the subcellular localization analysis. Gene expression showed that the KoOsmotin was induced primarily and highly in the leaves of K. obovata, but less abundantly in stems and roots. The overexpressing of KoOsmotin conferred cold tolerance in Escherichia coli cells. As we known, this is the first study to explore the osmotin of K. obovata. Our study provided valuable clues for further exploring the function of KoOsmotin response to stress.

中文翻译：

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冷胁迫下红树林植物Kandelia obovata KoOsmotin的克隆与表征

低温是一种主要的非生物胁迫，严重限制了红树林的生产力和分布。Kandelia obovata 是红树林植物中最耐寒的物种，但对其抗寒的分子机制知之甚少。Osmotin 是与植物中非生物和生物胁迫响应相关的关键蛋白质，但没有报道关于 K. obovata 中该基因的信息。在这项研究中，从红树林植物 K. obovata 中克隆了编码渗透素的 cDNA 序列 KoOsmotin（GenBank 登录号 KP267758）。KoOsmotin 蛋白由 221 个氨基酸组成，计算出的分子量为 24.11 kDa，pI 为 4.92。KoOsmotin 含有 16 个半胱氨酸残基和一个 N 端信号肽，它们是大多数渗透素和发病机制相关的 5 种蛋白质的常见特征。KoOsmotin 的三维 (3D) 模型包含一个 α-螺旋和 11 个 β-链，由三个特征域形成。KoOsmotin 的数据库比较显示与来自可可可可的 osmotin 34 最接近 (55.75%)。系统发育树还表明，KoOsmotin 聚集在 osmotin/OLP（类渗透蛋白）的分支中。亚细胞定位分析证明 KoOsmotin 蛋白定位于质膜和细胞质。基因表达表明，KoOsmotin 在 K. obovata 的叶子中主要和高度被诱导，但在茎和根中较少。KoOsmotin 的过表达赋予大肠杆菌细胞耐寒性。众所周知，这是第一项探索 K. obovata 渗透素的研究。