Desai M K, Mishra R N, Verma D, Nair S, Sopory S K, Reddy M K
International Center for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110 067, India.
Plant Physiol Biochem. 2006 Jul-Sep;44(7-9):483-93. doi: 10.1016/j.plaphy.2006.08.008. Epub 2006 Sep 5.
We have cloned and characterized a gene encoding voltage-dependent anion channel from Pennisetum glaucum (PgVDAC). PgVDAC was identified while isolating genes that were differentially up-regulated following salt stress. The genomic organization of PgVDAC clone was well conserved compared to other plant VDAC genes in terms of number of introns, their position and phasing, however, the primary amino acid sequence of voltage dependent anion channel (VDAC) proteins did not show much conservation with other plant VDACs but their secondary and tertiary structures are well conserved as predicted by in silico structural and CD spectra analyses and results show it to be a typical membrane-spanning beta-barrel leading to the formation of pore in the membrane. The heterologous expression of PgVDAC protein in yeast strain lacking the endogenous mitochondrial VDAC gene could not functionally complement it as was also previously observed for the potato VDAC. Using real-time quantitative PCR analysis it was found that transcript expression profile of PgVDAC was quantitatively and kinetically up-regulated in response to salinity, desiccation, cold and exogenous application of salicylic acid (SA); however, there was no effect of exogenous application of abscisic acid (ABA) on its expression. Constitutive over-expression of PgVDAC appears to be deleterious in transgenic rice plant; however, low level of up-regulation imparted salinity stress adaptive response. A search for a more suitable inducible transgene system is currently under way to understand PgVDAC expression levels in plant development and its role in stress adaptation.
我们已经克隆并鉴定了一个来自狼尾草（PgVDAC）的编码电压依赖性阴离子通道的基因。在分离盐胁迫后差异上调的基因时鉴定出了PgVDAC。与其他植物VDAC基因相比，PgVDAC克隆的基因组结构在内含子数量、位置和相位方面都得到了很好的保守，然而，电压依赖性阴离子通道（VDAC）蛋白的一级氨基酸序列与其他植物VDACs并没有太多的保守性，但其二级和三级结构通过计算机模拟结构和圆二色光谱分析预测得到了很好的保守，结果表明它是一种典型的跨膜β桶，导致在膜中形成孔道。正如之前在马铃薯VDAC中观察到的那样，在缺乏内源性线粒体VDAC基因的酵母菌株中异源表达PgVDAC蛋白不能在功能上互补。通过实时定量PCR分析发现，PgVDAC的转录本表达谱在盐度、干燥、寒冷和外源水杨酸（SA）处理下在数量和动力学上上调；然而，外源脱落酸（ABA）处理对其表达没有影响。PgVDAC的组成型过表达在转基因水稻植株中似乎是有害的；然而，低水平的上调赋予了盐胁迫适应性反应。目前正在寻找更合适的诱导转基因系统，以了解PgVDAC在植物发育中的表达水平及其在胁迫适应中的作用。
