Mechanism of vernal water-starwort, an amphibious plant, to change its form is revealed

July 29, 2021

Some species of the plants that grow on the water’s edge are known as amphibian species, which can grow both underwater and on land. Individual plants of amphibious species are known to produce completely different leaf forms depending on whether they are grown on land or underwater. What is called heterophylly, the ability to form different types of leaves depending on the environment, has long been attracting the interest of researchers. However, the mechanism of producing completely different forms of leaves has not been well known. A group from the University of Tokyo, RIKEN CSRS, and Nagoya University conducted research on the control mechanism of heterophylly using vernal water-starwort (Callitriche palustris L.), an aquatic plant in the family Plantain, which shows remarkable heterophylly.

C. palustris produces egg-shaped leaves when on land (terrestrial leaves) and ribbon-shaped leaves in water (underwater leaves). The underwater leaves are developed with elongation of each cell in leaves. The research group showed that cell growth of underwater leaves requires the actions of the plant hormones ethylene and gibberellic acid (GA). It was also found that the content of abscisic acid (ABA), another plant hormone, needs to be reduced. However, it was also found that these hormonal changes alone would not cause plants growing on land to produce underwater leaves. This suggests that the formation of underwater leaves requires some other factors that occur only when the plants are underwater.

The research group narrowed down the genes profoundly related to heterophylly by comprehensively comparing gene expression patterns under multiple cultivation conditions and by comparing gene expression patterns with related species without heterophylly. Some of these genes had been known to be involved in cell elongation in the model plant Arabidopsis. The study suggests that these genes work in a complex way, causing dramatic changes in leaf development patterns.

 

Original article
The Plant Cell doi:10.1093/plcell/koab192
H. Koga, M. Kojima, Y. Takebayashi, H. Sakakibara, H. Tsukaya,
"Identification of the unique molecular framework of heterophylly in the amphibious plant Callitriche palustris L.".

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Mikiko Kojima
Expert Technician
Mass Spectrometry and Microscopy Unit