College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
Department of Plant Sciences, University of Tennessee, Knoxville, TN, 37996, USA.
Sci Rep. 2017 Jun 23;7(1):4127. doi: 10.1038/s41598-017-03367-8.
Eukaryotes utilize Ca as a universal second messenger to convert and multiply environmental and developmental signals to downstream protein phosphorylation responses. However, the phylogenetic relationships of the genes that convert Ca signal (CS) to protein phosphorylation responses (PPRs) remain highly controversial, and their origin and evolutionary trajectory are unclear, which greatly hinders functional studies. Here we examined the deep phylogeny of eukaryotic CS converter gene families and identified a phylogenetically and structurally distinctive monophyly in Archaeplastida. This monophyly can be divided into four subfamilies, and each can be traced to ancestral members that contain a kinase domain and a calmodulin-like domain. This strongly indicates that the ancestor of this monophyly originated by a de novo fusion of a kinase gene and a calmodulin gene. This gene family, with a proposed new name, Calmodulin Fused Kinase (CFK), had expanded and diverged significantly both in sizes and in structures for efficient and accurate Ca signalling, and was shown to play pivotal roles in all the six major plant adaptation events in evolution. Our findings elucidated the common origin of all CS-PPR converter genes except CBL-CIPK converter genes, and revealed that CFKs act as the main CS conversion system in plants.
真核生物利用 Ca 作为通用的第二信使，将环境和发育信号转化和放大为下游蛋白磷酸化反应。然而，将 Ca 信号 (CS) 转换为蛋白磷酸化反应 (PPR) 的基因的系统发育关系仍存在很大争议，其起源和进化轨迹尚不清楚，这极大地阻碍了功能研究。在这里，我们研究了真核生物 CS 转化基因家族的深层系统发育，在古菌域中鉴定出一个在系统发育和结构上都具有独特单系性的基因家族。这个单系性可以分为四个亚科，每个亚科都可以追溯到含有激酶结构域和钙调蛋白样结构域的祖先成员。这强烈表明，这个单系性的祖先起源于一个激酶基因和钙调蛋白基因的从头融合。这个基因家族，我们提出了一个新的名称，钙调蛋白融合激酶（CFK），在大小和结构上都显著扩张和分化，以实现高效和准确的 Ca 信号传递，并被证明在进化过程中的所有六大植物适应事件中都发挥着关键作用。我们的研究结果阐明了除 CBL-CIPK 转化基因以外的所有 CS-PPR 转化基因的共同起源，并揭示了 CFKs 是植物中主要的 CS 转换系统。
