Aquatic plants are an important group in water and play a crucial role in maintaining the stability of aquatic ecosystems. Due to frequent environmental changes, such as water level fluctuations, many aquatic plants have evolved "heterophylly", which means that plants with the same genotype can produce significantly different leaf shapes in different environments. Specifically, the submerged leaves of heterophyllous plants are often deeply lobed, filamentous, or linear, with low or missing stomatal density. 

In contrast, terrestrial leaves have a simpler shape, well-developed vascular bundles, and higher stomatal density. The heterophylly of aquatic plants are an ideal model for studying plant phenotypes and environmental adaptation. However, research into their evolutionary patterns and regulatory mechanisms is still insufficient due to the lack of suitable model plants. 

Recently, a research group led by Prof. HOU Hongwei from the Institute of Hydrobiology (IHB) of the Chinese Academy of Sciences reported the genome of Water-wisteria (Hygrophila difformis), relying the evolution and adaptation of aquatic plants to the amphibious environment. This study was published in Plant, Cell & Environment. 

In this study, the researchers sequenced and assembled the H. difformis chromosome-level genome (scaffold N50: 60.43 Mb, genome size: 871.92 Mb), revealing 36,099 predicted protein-coding genes distributed over 15 pseudochromosomes. Evolution analysis indicated that H. difformis diverged from its relatives during the Oligocene climate-change period and expanded gene families related to its amphibious habit. 

The researchers also performed transcriptome analysis, revealing that genes related to environmental stimuli, leaf development, and other pathways were differentially expressed under submerged and terrestrial conditions, possibly modulating morphological and physiological acclimation to changing environments.

Additionally, the researchers discovered candidate genes that respond to different environmental conditions and elucidated the role of LATE MERISTEM IDENTITY 1 (LMI1) in heterophylly.

This study reveals the phenotype, structure and molecular adaptation of the aquatic plant H. difformis, establishing this plant as a model for studying interconnections between environmental adaptation and morphogenesis.

(Editor: MA Yun)