The ABA-mediated switch between submersed and emersed life-styles in aquatic macrophytes

Abstract

Hydrophytes comprise aquatic macrophytes from various taxa that are able to sustain and to complete their lifecycle in a flooded environment. Their ancestors, however, underwent adaptive processes to withstand drought on land and became partially or completely independent of water for sexual reproduction. Interestingly, the step backwards into the high-density aquatic medium happened independently several times in numerous plant taxa. For flowering plants, this submersed life-style is especially difficult as they need to erect their floral organs above the water surface to be pollinated. Moreover, fresh-water plants evolved the adaptive mechanism of heterophylly, which enabled them to switch between a submersed and an emersed leaf morphology. The plant hormone abscisic acid (ABA) is a key factor of heterophylly induction in aquatic plants and is a major switch between a submersed and emersed life. The mechanisms of ABA signal perception and transduction appear to be conserved throughout the evolution of basal plants to angiosperms and from terrestrial to aquatic plants. This review summarizes the interplay of environmental factors that act through ABA to orchestrate adaptation of plants to their aquatic environment.

Regulation of the KNOX-GA Gene Module Induces Heterophyllic Alteration in North American Lake Cress

“…Parallels are seen between this situation and that of leaf complexity, where other mechanisms besides the KNOX-GA gene module have been shown to operate in a derived clade of Fabaceae (Hofer et al, 1997;Champagne et al, 2007;Zhou et al, 2014). Since the acquisition of heterophylly has also occurred independently multiple times (Wells and Pigliucci, 2000;Wanke, 2011;Nakayama et al, 2012a), the core regulatory mechanisms for acquisition of heterophylly may not be conserved during evolution.…”

“…Some leaf form alterations are thought to be an adaptive response to the environment (Cook and Johnson, 1968). In addition, heterophylly is seen across diverse plant species (Wells and Pigliucci, 2000;Wanke, 2011;Nakayama et al, 2012a). Hence, heterophylly provides a good model to understand geneenvironment interactions (Pigliucci, 2010).…”

Molecular Phylogeny Determined Using Chloroplast DNA Inferred a New Phylogenetic Relationship of <i>Rorippa aquatica</i> (Eaton) EJ Palmer & Steyermark (Brassicaceae)—Lake Cress

“…They exhibit forms with weak serrate or deep lobed margins in terrestrial environments and become pinnately compound in submerged aquatic environments (Figures 1(D)-(G)) [7,8]. Although heterophylly is widely noted among diverse plant species from ferns to angiosperms [8][9][10], little is known about the mechanism that regulates this phenomenon, because of the lack of an adequate model species. A previous study indicated that lake cress has some advantages as a model for studying heterophylly, such as plant size, easy maintenance, and systematic positioning (closely related to Arabidopsis) [8].…”

Leaves may function as temperature sensors in the heterophylly of Rorippa aquatica (Brassicaceae)

“…3 Several plants showing heterophylly have been described and the underlying mechanisms have been investigated. 1,4,5 These studies have shown that various hormones, such as ethylene and abscisic acid, are involved in the alteration of leaf form.…”