Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA.
Plant Cell. 2009 Oct;21(10):3350-67. doi: 10.1105/tpc.109.070607. Epub 2009 Oct 9.
The Arabidopsis thaliana histone H2A-1 is important for Agrobacterium tumefaciens-mediated plant transformation. Mutation of HTA1, the gene encoding histone H2A-1, results in decreased T-DNA integration into the genome of Arabidopsis roots, whereas overexpression of HTA1 increases transformation frequency. To understand the mechanism by which HTA1 enhances transformation, we investigated the effects of overexpression of numerous Arabidopsis histones on transformation and transgene expression. Transgenic Arabidopsis containing cDNAs encoding histone H2A (HTA), histone H4 (HFO), and histone H3-11 (HTR11) displayed increased transformation susceptibility, whereas histone H2B (HTB) and most histone H3 (HTR) cDNAs did not increase transformation. A parallel increase in transient gene expression was observed when histone HTA, HFO, or HTR11 overexpression constructs were cotransfected with double- or single-stranded forms of a gusA gene into tobacco (Nicotiana tabacum) protoplasts. However, these cDNAs did not increase expression of a previously integrated transgene. We identified the N-terminal 39 amino acids of H2A-1 as sufficient to increase transient transgene expression in plants. After transfection, transgene DNA accumulates more rapidly in the presence of HTA1 than with a control construction. Our results suggest that certain histones enhance transgene expression, protect incoming transgene DNA during the initial stages of transformation, and subsequently increase the efficiency of Agrobacterium-mediated transformation.
拟南芥组蛋白 H2A-1 对根癌农杆菌介导的植物转化至关重要。编码组蛋白 H2A-1 的 HTA1 基因突变导致 T-DNA 整合到拟南芥根基因组中的减少，而 HTA1 的过表达增加转化频率。为了了解 HTA1 增强转化的机制，我们研究了过量表达许多拟南芥组蛋白对转化和转基因表达的影响。含有编码组蛋白 H2A（HTA）、组蛋白 H4（HFO）和组蛋白 H3-11（HTR11）的 cDNA 的转基因拟南芥表现出增加的转化易感性，而组蛋白 H2B（HTB）和大多数组蛋白 H3（HTR）cDNA 不会增加转化。当 HTA、HFO 或 HTR11 过表达构建体与双链或单链形式的 gusA 基因共转染到烟草（Nicotiana tabacum）原生质体中时，观察到瞬时基因表达的平行增加。然而，这些 cDNA 并没有增加先前整合的转基因的表达。我们确定 H2A-1 的 N 端 39 个氨基酸足以增加植物中转基因的瞬时表达。转染后，与对照构建体相比，在存在 HTA1 的情况下，转基因 DNA 更快地积累。我们的结果表明，某些组蛋白增强了转基因的表达，在转化的初始阶段保护传入的转基因 DNA，随后提高了根癌农杆菌介导的转化效率。
