The adaptive evolution of Euryale ferox to the aquatic environment through paleo-hexaploidization

第一作者：Peng Wu

第一单位：扬州大学

第一通讯：Liangjun Li

 Abstarct 

背景回顾：Occupation of living space is one of the main driving forces of adaptive evolution, especially for aquatic plants whose leaves float on the water surface and thus have limited living space. Euryale ferox, from the angiosperm basal family Nymphaeaceae, develops large, rapidly expanding leaves to compete for space on the water surface. Microscopic observation found that the cell proliferation of leaves is almost completed underwater, while the cell expansion occurs rapidly after they grows above water. 

对生存空间的占据是适应性演化的主要驱动力之一，尤其是对于叶片漂浮于水面上的水生植物，其生存空间相对有限。芡实（Euryale ferox）属于基础被子植物睡莲科的物种，其具有巨大且能够迅速扩张的叶片，在水面上争夺生活空间。显微镜观察发现，芡实叶片的细胞增殖几乎在水下就已完成，在叶片达到水面之上后细胞迅速发生扩张。

主要研究：To explore the mechanism underlying the specific development of leaves, we performed sequences assembly and analyzed the genome and transcriptome dynamics of E. ferox. 

为了探索芡实叶片的特异性发育机制，作者对芡实的基因组进行了测序、组装以及转录组动态分析。

结果1-亚基因组重构及适应性演化：Through reconstruction of the three sub-genomes generated from the paleo-hexaploidization event in E. ferox, we revealed that one sub-genome was phylogenetically closer to Victoria cruziana, which also exhibits gigantic floating leaves. Further analysis revealed that while all three sub-genomes promoted the evolution of the specific leaf development in E. ferox, the genes from the sub-genome closer to V. cruziana contributed more to this adaptive evolution. 

通过对芡实的古六倍化事件产生的3套亚基因组进行重构，作者发现其中一套亚基因组与克鲁兹王莲（Victoria cruziana）更加近缘，而克鲁兹王莲也具有较大的漂浮叶。进一步的分析表明，虽然3个亚基因组都促进了芡实特化叶片发育的演化，但是来自与克鲁兹王莲更加近缘的亚基因组对于该性状的适应性演化贡献更多。

结果2-功能基因：Moreover, we found that genes involved in cell proliferation and expansion, photosynthesis, and energy transportation were over-retained and showed strong expression association with the leaf development stages, such as the expression divergence of SWEET orthologs as energy uploaders and unloaders in the sink and source leaf organs of E. ferox. 

此外，作者还发现参与细胞增殖和扩张、光合作用以及能量运输的基因被过度的保留，并且这些基因的表达模式与叶片的发育存在较强的关联性，比如SWEETs蛋白的表达分化，分别在芡实的“源”和“库”叶片器官中负责能量的装载运输和卸载利用。

结论：These findings provide novel insights into the genome evolution through polyploidization, as well as the adaptive evolution regarding the leaf development accomplished through biased gene retention and expression sub-functionalization of multi-copy genes in E. ferox.

本文的研究结果为植物多倍化后的基因组演化提供新的视野，以及芡实中通过对多拷贝基因的偏性基因保留和表达亚功能化实现叶片功能的适应性演化提供参考。

** 李良俊 **  

doi: https://doi.org/10.1111/tpj.15717

Journal: the plant journal

Published date: February 25, 2022