Department of Plant Biotechnology, Agricultural Plant Stress Research Center and Biotechnology Research Institute, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Republic of Korea.
Plant Physiol Biochem. 2010 Oct-Nov;48(10-11):866-72. doi: 10.1016/j.plaphy.2010.08.013. Epub 2010 Sep 8.
Among the three zinc finger-containing glycine-rich RNA-binding proteins, named AtRZ-1a, AtRZ-1b, and AtRZ-1c, in the Arabidopsis thaliana genome, AtRZ-1a has previously been shown to enhance cold and freezing tolerance in Arabidopsis. Here, we determined and compared the functional roles of AtRZ-1b and AtRZ-1c in Arabidopsis and Escherichia coli under cold stress conditions. AtRZ-1b, but not AtRZ-1c, successfully complemented the cold sensitivity of E. coli BX04 mutant cells lacking four cold shock proteins. Domain deletion and site-directed mutagenesis showed that the zinc finger motif of AtRZ-1b is important for its complementation ability, and that the truncated N- and C-terminal domains of AtRZ-1b and AtRZ-1c harbor the complementation ability. Despite an increase in transcript levels of AtRZ-1b and AtRZ-1c under cold stress, overexpression or loss-of-function mutations did not affect seed germination or seedling growth of Arabidopsis under cold stress conditions. AtRZ-1b and AtRZ-1c proteins, being localized to the nucleus, have been shown to bind non-specifically to RNA sequences in vitro, in comparison to AtRZ-1a that is localized to both the nucleus and the cytoplasm and binds preferentially to G- or U-rich RNA sequences. Taken together, these results demonstrate that the three AtRZ-1 family members showing different cellular localization and characteristic nucleic acid-binding property have a potential to contribute differently to the enhancement of cold tolerance in Arabidopsis and E. coli.
在拟南芥基因组中的三个含锌指的甘氨酸丰富 RNA 结合蛋白（命名为 AtRZ-1a、AtRZ-1b 和 AtRZ-1c）中，先前已表明 AtRZ-1a 可增强拟南芥的抗冷性和抗冻性。在这里，我们确定并比较了 AtRZ-1b 和 AtRZ-1c 在拟南芥和大肠杆菌中在冷应激条件下的功能作用。AtRZ-1b 但不是 AtRZ-1c 成功地补充了缺乏四种冷休克蛋白的大肠杆菌 BX04 突变细胞的冷敏感性。结构域缺失和定点突变表明，AtRZ-1b 的锌指基序对其互补能力很重要，并且 AtRZ-1b 和 AtRZ-1c 的截短的 N-和 C-末端结构域具有互补能力。尽管 AtRZ-1b 和 AtRZ-1c 的转录水平在冷胁迫下增加，但过表达或功能丧失突变不会影响冷胁迫条件下拟南芥的种子萌发或幼苗生长。AtRZ-1b 和 AtRZ-1c 蛋白定位于细胞核内，与定位于细胞核和细胞质的 AtRZ-1a 相比，能够在体外非特异性地结合 RNA 序列，并且 AtRZ-1a 优先结合富含 G 或 U 的 RNA 序列。总的来说，这些结果表明，这三个 AtRZ-1 家族成员表现出不同的细胞定位和特征性核酸结合特性，有可能以不同的方式对增强拟南芥和大肠杆菌的抗冷性做出贡献。
