Pils Birgit, Heyl Alexander
Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom.
Plant Physiol. 2009 Oct;151(2):782-91. doi: 10.1104/pp.109.139188. Epub 2009 Aug 12.
The conquest of the land by plants required dramatic morphological and metabolic adaptations. Complex developmental programs under tight regulation evolved during this process. Key regulators of plant development are phytohormones, such as cytokinins. Cytokinins are adenine derivatives that affect various processes in plants. The cytokinin signal transduction system, which is mediated via a multistep variant of the bacterial two-component signaling system, is well characterized in the model plant Arabidopsis (Arabidopsis thaliana). To understand the origin and evolutionary pattern of this signaling pathway, we surveyed the genomes of several sequenced key plant species ranging from unicellular algae, moss, and lycophytes, to higher land plants, including Arabidopsis and rice (Oryza sativa), for proteins involved in cytokinin signal transduction. Phylogenetic analysis revealed that the hormone-binding receptor and a class of negative regulators first appeared in land plants. Other components of the signaling pathway were present in all species investigated. Furthermore, we found that the receptors evolved under different evolutionary constraints from the other components of the pathway: The number of receptors remained fairly constant, while the other protein families expanded.
植物对陆地的征服需要显著的形态和代谢适应。在这一过程中，受到严格调控的复杂发育程序逐渐演化。植物发育的关键调节因子是植物激素，如细胞分裂素。细胞分裂素是腺嘌呤衍生物，影响植物的各种生理过程。细胞分裂素信号转导系统通过细菌双组分信号系统的多步骤变体介导，在模式植物拟南芥（Arabidopsis thaliana）中已得到充分表征。为了了解该信号通路的起源和进化模式，我们对从单细胞藻类、苔藓、石松到高等陆地植物（包括拟南芥和水稻（Oryza sativa））等几种已测序的关键植物物种的基因组进行了调查，寻找参与细胞分裂素信号转导的蛋白质。系统发育分析表明，激素结合受体和一类负调控因子首次出现在陆地植物中。信号通路的其他组分存在于所有被研究的物种中。此外，我们发现受体的进化受到的限制与信号通路的其他组分不同：受体的数量保持相当恒定，而其他蛋白质家族则有所扩展。
