东南景天捕光叶绿素a/b结合蛋白基因SaLhcb2的分离及功能

LHCB基因对植物适应各种环境胁迫的过程中起着重要作用。序列分析显示:东南景天Sedum alfredii的SaLhcb2基因全长929 bp, 其中开放阅读框(ORF)为798 bp, 含有1个74 bp的内含子。通过蛋白序列比对, SaLhcb2基因编码的蛋白与多种植物的蛋白序列同源性都很高(92%以上)。分析400 μmol·L-1镉离子(Cd2+), 铜离子(Cu2+)和铅离子(Pb2+)胁迫处理后的东南景天, 结果显示:镉处理后SaLhcb2基因在茎、叶中表达量快速上升(12.0 h内), 根中表达量到48.0 h后才上调。铜处理后0.5 h根中表达显著上调, 胁迫6.0 h后茎中表达量显著上调, 随后一直降低, 叶片中该基因表达量一直较低。铅处理后, 根中表达量降低, 96.0 h左右比对照略微上调, 而茎中96.0 h内表达量相比对照都上调, 叶片中96.0 h内都降低。研究结果表明:SaLhcb2与东南景天的镉、铜、铅胁迫抗性有密切的相关性。

Characterization of a light-harvesting chlorophyll a/b binding protein (LHCB) gene, SaLhcb2, in Sedum alfredii

The light-harvesting chlorophyll a/b binding protein (LHCB) gene plays an important role in plants adapting to various environments. Sedum alfredii is a new Zn/Cd hyper-accumulator and whether LHCB in this interesting species was related to the heavy-metal tolerance interested us a lot. In the present study, we isolated a cDNA using homologous cloning and designated it as SaLhcb2 which encoded a light-harvesting chlorophyll a/b binding protein in Sedum alfredii. A prelimary sequence analysis was conducted and homologous comparison was also performed using MegAlign. In order to identify the gene expression profiles of SaLhcb2 response to heavy-metal stress, seedlings of Sedum alfredii were treated by 400 μmol·L-1 Cd2+, Cu2+, and Pb2+ stresses with those cultured in water as a control. Roots, stems and leaves were dissected and promptly frozen in liquid nitrogen for RNA extraction and the followed real-time PCR. Sequence analysis showed that the coding sequence of SaLhcb2 was 929 bp and the open reading frame was 798 bp. The deduced protein, SaLHCB2, consisted of 266 amino acids and had a high homology (above 92%) with LHCB2 of other plants via homologous comparison. For the Cd2+, Cu2+, and Pb2+ stress treatments, the level of SaLhcb2 was elevated dramatically in stems and leaves within 12.0 h. However, with the Cd2+ treatment, the expression of SaLhcb2 in roots did not display a tendency of up-regulation until 48.0 h. For the Cu2+ treatment, in roots, the expression of SaLhcb2 showed a prompt response of up-regulation at 0.5 h and then decreased weirdly. With the Pb2+ treatment, the expression of SaLhcb2 in roots displayed a profile of down-regulation except the point of 96.0 h. Based on the above findings, it could be concluded that the expression of SaLhcb2 in Sedum alfredi was influenced by heavy-metal treatment and may function in the process of plants combating heavy-metal stress.