Adaptation to aquatic habitats is a formidable challenge for terrestrial angiosperms that has long intrigued scientists. Compared with terrestrial angiosperms, aquatic plants occupy a distinctive and in some way more stressful ecological environment, including low light levels, reduced carbon availability, sediment anoxia and mechanical damage through wave exposure. Aquatic plants have adapted various life forms requiring different levels of physical change from terrestrial plants. Given these challenges and physical changes, the adaptive strategies of aquatic plants have long intrigued scientists. 

Ranunculus L. (Ranunculaceae) serves as a well-studied lineage that can be used as a genomic model for the study of plant adaptations from terrestrial to aquatic habitats. 

Supervised by Prof. WANG Qingfeng from the Adaptive Evolution of Aquatic Plants Research Group, Wuhan Botanical Garden (WBG), CHEN Lingyun and his colleagues isolated transcriptomes of the aquatic plant Ranunculus bungei, and two terrestrial plant R. Sceleratus, R. Brotherusii using the Illumina paired-end sequencing technology.

Orthologous genes among the three species were selected by using Bidirectional Best Hit method and OrthoMCL method. Non-synonymous/synonymous (d_N/d_S) analyses were performed with a maximum likelihood method and an approximate method for the three species-pairs.  

14 genes of R. bungei were detected to be potentially involved in the adaption from terrestrial to aquatic habitats. Some of the homologs to these genes in  the three Ranunculus species were involved in vacuole protein formation, regulating "water transport process" and "microtubule cytoskeleton organization". 

This research enlightens understanding of the molecular mechanism of plant adaptation from terrestrial to aquatic habitat

This study was funded by the Chinese Academy of Sciences, and National Natural Science Foundation of China. Relevant results were published in Scientific Reports entitiled "Transcriptome sequencing of three Ranunculus species (Ranunculaceae) reveals candidate genes in adaptation from terrestrial to aquatic habitats". 

Numbers of positively selected genes (PSGs) shared among species-pairs (Image by WBG)