Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan, ROC.
Plant Cell Physiol. 2010 Dec;51(12):2132-44. doi: 10.1093/pcp/pcq172. Epub 2010 Nov 21.
Proteins abundant in seeds during the late stages of development, late embryogenesis abundant (LEA) proteins, are associated with desiccation tolerance. More than 100 of the group I LEA genes, also termed Em genes, have been identified from plants, bacteria and animals. The wide distribution indicates the functional importance of these genes. In the present study, we characterized a novel Em-like gene, OsLEA1a of rice (Oryza sativa). The encoded OsLEA1a protein has an N-terminal sequence similar to that of other plant Em proteins but lacks a 20-mer motif that is the most significant feature of typical Em proteins. The location of the sole intron indicates that the second exon of OsLEA1a is the mutated product of a typical Em gene. Transcriptome analysis revealed OsLEA1a mainly expressed in embryos, with no or only a few transcripts in osmotic stress-treated vegetative tissues. Structural analysis revealed that the OsLEA1a protein adopts high amounts of disordered conformations in solution and undergoes desiccation-induced conformational changes. Macromolecular interaction studies revealed that OsLEA1a protein interacts with non-reducing sugars and phospholipids but not poly-l-lysine. Thus, although the OsLEA1a protein lost its 20-mer motif, it is still involved in the formation of bioglasses with non-reducing sugars or plasma membrane. However, the protein does not function as a chaperone as do other groups of hydrophilic LEA proteins. The orthologs of the OsLEA1a gene had been identified from various grasses but not in dicot plants. Genetic analysis indicated that rice OsLEA1a locates at a 193 kb segment in chromosome 1 and is conserved in several published cereal genomes. Thus, the ancestor of Em-like genes might have evolved after the divergence of monocot plants.
在发育后期种子中丰富的蛋白质，即晚期胚胎丰富（LEA）蛋白，与干燥耐受性有关。已经从植物、细菌和动物中鉴定出超过 100 种 I 组 LEA 基因，也称为 Em 基因。这些基因的广泛分布表明了它们的功能重要性。在本研究中，我们对水稻（Oryza sativa）的一个新的 Em 样基因 OsLEA1a 进行了表征。编码的 OsLEA1a 蛋白具有与其他植物 Em 蛋白相似的 N 端序列，但缺乏典型 Em 蛋白的最显著特征——20 个氨基酸的基序。唯一内含子的位置表明，OsLEA1a 的第二外显子是典型 Em 基因的突变产物。转录组分析显示，OsLEA1a 主要在胚胎中表达，在渗透胁迫处理的营养组织中几乎没有或只有少量转录本。结构分析表明，OsLEA1a 蛋白在溶液中采用大量无序构象，并经历干燥诱导的构象变化。大分子相互作用研究表明，OsLEA1a 蛋白与非还原糖和磷脂相互作用，但不与聚赖氨酸相互作用。因此，尽管 OsLEA1a 蛋白失去了 20 个氨基酸的基序，但它仍然参与非还原糖或质膜的生物玻璃的形成。然而，该蛋白不像其他亲水 LEA 蛋白组那样作为分子伴侣发挥作用。OsLEA1a 基因的同源基因已经从各种禾本科植物中鉴定出来，但在双子叶植物中没有。遗传分析表明，水稻 OsLEA1a 位于 1 号染色体上的 193 kb 片段，在几个已发表的谷类基因组中保守。因此，Em 样基因的祖先可能是在单子叶植物分化后进化而来的。
