Hummel Irène, Gouesbet Gwenola, El Amrani Abdelhak, Aïnouche Abdelkader, Couée Ivan
Centre National de la Recherche Scientifique, Université de Rennes 1, UMR 6553 ECOBIO, Campus de Beaulieu, bâtiment 14A, F-35042 Rennes Cedex, France.
Gene. 2004 Nov 24;342(2):199-209. doi: 10.1016/j.gene.2004.08.024.
Arginine decarboxylase (ADC) is a key enzyme involved in the synthesis of polyamines, which have been implicated in developmental processes and stress responses in higher plants. An ancestral ADC gene appears to have been duplicated at the origin of the Brassicaceae family, thus yielding two paralogues in the derived taxa. ADC gene structure was investigated in Pringlea antiscorbutica R. Br., a geographically isolated Brassicaceae species that is endemic from the subantarctic region. P. antiscorbutica exhibits several biochemical and physiological adaptations related to this cold and harsh environment, including high levels of polyamines, which is unusual in higher plants, and especially high levels of agmatine, the product of the ADC-catalysed reaction. Various ADC clones were obtained from P. antiscorbutica. Sequence and phylogenetic analysis showed that all these clones fitted with the presence of two paralogues, PaADC1 and PaADC2, in P. antiscorbutica. Expression of these ADC paralogues was analyzed in P. antiscorbutica during vegetative development and response to stress. Whereas PaADC2 was expressed at both seedling and mature stages, PaADC1 transcripts were hardly detected during early development and were significantly expressed in mature plants. Moreover, PaADC2, but not PaADC1, expression was up-regulated in response to chilling and salt stress at seedling stage. Analysis of 5' regulatory regions of these ADC genes revealed several differences in putative cis-regulatory elements, which could be associated with specific expression patterns. These results were compared to ADC paralogue expression in Arabidopsis thaliana and are discussed in the evolutionary context of genetic diversity resulting from gene duplication.
精氨酸脱羧酶（ADC）是参与多胺合成的关键酶，多胺与高等植物的发育过程和应激反应有关。一个祖先ADC基因似乎在十字花科起源时发生了复制，从而在衍生类群中产生了两个旁系同源基因。对极地羽衣甘蓝（Pringlea antiscorbutica R. Br.）的ADC基因结构进行了研究，极地羽衣甘蓝是十字花科的一个地理隔离物种，特产于亚南极地区。极地羽衣甘蓝表现出与这种寒冷恶劣环境相关的几种生化和生理适应性，包括高水平的多胺（这在高等植物中并不常见），尤其是高水平的胍丁胺（ADC催化反应的产物）。从极地羽衣甘蓝中获得了各种ADC克隆。序列和系统发育分析表明，所有这些克隆都符合极地羽衣甘蓝中存在两个旁系同源基因PaADC1和PaADC2的情况。在极地羽衣甘蓝的营养发育和应激反应过程中分析了这些ADC旁系同源基因的表达。虽然PaADC2在幼苗期和成熟期均有表达，但在早期发育过程中几乎检测不到PaADC1的转录本，而在成熟植株中显著表达。此外，在幼苗期，PaADC2的表达受低温和盐胁迫上调，而PaADC1不受影响。对这些ADC基因5'调控区的分析揭示了推定的顺式调控元件中的几个差异，这可能与特定的表达模式有关。将这些结果与拟南芥中ADC旁系同源基因的表达进行了比较，并在基因复制导致的遗传多样性的进化背景下进行了讨论。
