Saavedra Laura, Svensson Jan, Carballo Valentina, Izmendi Darwin, Welin Björn, Vidal Sabina
Laboratorio de Biología Molecular Vegetal, Facultad de Ciencias, Universidad de la República, Iguá 4225, CP 11400, Montevideo, Uruguay.
Plant J. 2006 Jan;45(2):237-49. doi: 10.1111/j.1365-313X.2005.02603.x.
We isolated a dehydrin-like (DHN-like) gene fragment, PpDHNA, from the moss Physcomitrella patens by PCR amplification using degenerate primers directed against conserved amino acid segments of DHNs of higher plants. The full-length cDNA was found to encode a 59.2-kDa glycine-rich protein, DHNA, with typical characteristics of DHNs, including the presence of several Y repeats and one conserved K segment. DHNA had a high sequence similarity with a protein from Tortula ruralis, Tr288, which is thought to be involved in cellular dehydration tolerance/repair in this moss. Northern and Western analysis showed that PpDHNA is upregulated upon treatment of plants with abscisic acid, NaCl or mannitol, indicating a similar expression pattern to DHNs from higher plants. To analyze the contribution of DHNA to osmotic stress tolerance, we generated a knockout mutant (dhnA) by disruption of the gene using homologous recombination. Growth and stress response studies of the mutant showed that dhnA was severely impaired in its capacity to resume growth after salt and osmotic-stress treatments. We provide direct genetic evidence in any plant species for a DHN exerting a protective role during cellular dehydration allowing recovery when returned to optimal growth conditions.
我们使用针对高等植物脱水素（DHN）保守氨基酸片段的简并引物，通过PCR扩增从藓类植物小立碗藓中分离出一个类脱水素（DHN-like）基因片段PpDHNA。发现该全长cDNA编码一个59.2 kDa的富含甘氨酸的蛋白DHNA，其具有DHN的典型特征，包括存在几个Y重复序列和一个保守的K片段。DHNA与来自扭口藓的一种蛋白Tr288具有高度的序列相似性，据认为该蛋白参与了这种藓类植物的细胞脱水耐受性/修复过程。Northern和Western分析表明，用脱落酸、NaCl或甘露醇处理植物后，PpDHNA的表达上调，这表明其表达模式与高等植物的DHN相似。为了分析DHNA对渗透胁迫耐受性的贡献，我们通过同源重组破坏该基因，构建了一个敲除突变体（dhnA）。对该突变体的生长和胁迫反应研究表明，dhnA在盐胁迫和渗透胁迫处理后恢复生长的能力严重受损。我们在任何植物物种中提供了直接的遗传学证据，证明一种DHN在细胞脱水期间发挥保护作用，使植物在恢复到最佳生长条件时能够恢复生长。
