Lildballe Dorte Launholt, Pedersen Dorthe S, Kalamajka Rainer, Emmersen Jeppe, Houben Andreas, Grasser Klaus D
Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark.
J Mol Biol. 2008 Dec 5;384(1):9-21. doi: 10.1016/j.jmb.2008.09.014. Epub 2008 Sep 16.
High mobility group (HMG) proteins of the HMGB family are small and relatively abundant chromatin-associated proteins. As architectural factors, the HMGB proteins are involved in the regulation of transcription and other DNA-dependent processes. We have examined Arabidopsis mutant plants lacking the HMGB1 protein, which is a typical representative of the plant HMGB family. In addition, our analyses included transgenic plants overexpressing HMGB1 and mutant plants that were transformed with the HMGB1 genomic region (complementation plants), as well as control plants. Both the absence and overexpression of HMGB1 caused shorter primary roots and affected the sensitivity towards the genotoxic agent methyl methanesulfonate. The overexpression of HMGB1 decreased the seed germination rate in the presence of elevated concentrations of NaCl. The complementation plants that expressed HMGB1 at wild-type levels did not show phenotypic differences compared to the control plants. Transcript profiling by microarray hybridization revealed that a remarkably large number of genes were differentially expressed (up- and down-regulated) in plants lacking HMGB1 compared to control plants. Among the down-regulated genes, the gene ontology category of stress-responsive genes was overrepresented. Neither microscopic analyses nor micrococcal nuclease digestion experiments revealed notable differences in overall chromatin structure, when comparing chromatin from HMGB1-deficient and control plants. Collectively, our results show that despite the presence of several other HMGB proteins, the lack and overexpression of HMGB1 affect certain aspects of plant growth and stress tolerance and it has a marked impact on the transcriptome, suggesting that HMGB1 has (partially) specialized functions in Arabidopsis.
高迁移率族（HMG）蛋白家族中的HMGB蛋白是一类体积较小且相对丰富的与染色质相关的蛋白。作为结构因子，HMGB蛋白参与转录调控及其他依赖DNA的过程。我们研究了缺乏HMGB1蛋白的拟南芥突变体植株，HMGB1蛋白是植物HMGB家族的典型代表。此外，我们的分析还包括过表达HMGB1的转基因植株、用HMGB1基因组区域转化的突变体植株（互补植株）以及对照植株。HMGB1的缺失和过表达均导致主根变短，并影响对基因毒性试剂甲磺酸甲酯的敏感性。在高浓度NaCl存在的情况下，HMGB1的过表达降低了种子萌发率。与对照植株相比，以野生型水平表达HMGB1的互补植株未表现出表型差异。通过微阵列杂交进行的转录谱分析表明，与对照植株相比，缺乏HMGB1的植株中有大量基因差异表达（上调和下调）。在下调基因中，应激反应基因的基因本体类别占比过高。在比较HMGB1缺陷植株和对照植株的染色质时，显微镜分析和微球菌核酸酶消化实验均未发现整体染色质结构有明显差异。总体而言，我们的结果表明，尽管存在其他几种HMGB蛋白，但HMGB1的缺失和过表达会影响植物生长和胁迫耐受性的某些方面，并且对转录组有显著影响，这表明HMGB1在拟南芥中具有（部分）特殊功能。
