Aquatic plants have evolved heterophylly to adapt to the environmental changes in water level. The terrestrial leaves of heterophyllous plants have simple leaf shapes and high stomatal density, while aquatic leaves have evolved deeply lobed and linear leaves, with reduced stomatal density. In recent years, research on the mechanisms of heterophylly in aquatic plants has been well conducted. However, whether regulatory mechanisms in various aquatic plants are specific or conserved are still controversial.

Recently, a research group led by Prof. HOU Hongwei from the Institute of Hydrobiology (IHB) of the Chinese Academy Sciences found that aquatic plants share common regulation of heterophylly through morphological regulation genes. This study was published in Plant & Cell Physiology.

The researchers first performed RNAseq of eight aquatic species, and found that the KNOX1 gene, which regulates leaf shape development, is generally up-regulated in the aquatic leaves. Subsequently, overexpressing these KNOX1 genes from different species led to similar complex leaves in Arabidopsis, indicating their conserved abilities to promote leaf shape complexity.

Further analyses showed that abscisic acid treatment can significantly induce terrestrial leaf shape in aquatic plants of seven species, which may be a key hormone promoting their terrestrial leaf development. These plants showed a decrease in stomatal density after submerged treatment, which may be due to the down-regulation of genes related to stomatal development.

Additionally, the team compared the leaf shape differences of multiple species in different environments and discovered that dissection index (DI) can significantly distinguish leaf shape variations, which can serve as a unified indicator for quantifying leaf shape variations of aquatic plants.

These findings reveal common characteristics and regulations among eight aquatic eudicots, providing resources to reveal mechanisms of heterophylly and convergent evolution.

Conserved mechanisms of heterophylly regulation in aquatic plants (Image by IHB)

(Editor: MA Yun)