Genome-Wide Analysis of the Growth-Regulating Factor (GRF) Family in Aquatic Plants and Their Roles in the ABA-Induced Turion Formation of Spirodela polyrhiza

Abstract

Growth-regulating factors (GRFs) are plant-specific transcription factors that play essential roles in regulating plant growth and stress response. The GRF gene families have been described in several terrestrial plants, but a comprehensive analysis of these genes in diverse aquatic species has not been reported yet. In this study, we identified 130 GRF genes in 13 aquatic plants, including floating plants (Azolla filiculoides, Wolffia australiana, Lemna minuta, Spirodela intermedia, and Spirodela polyrhiza), floating-leaved plants (Nymphaea colorata and Euryale ferox), submersed plants (Zostera marina, Ceratophyllum demersum, Aldrovanda vesiculosa, and Utricularia gibba), an emergent plant (Nelumbo nucifera), and an amphibious plant (Cladopus chinensis). The gene structures, motifs, and cis-acting regulatory elements of these genes were analyzed. Phylogenetic analysis divided these GRFs into five clusters, and ABRE cis-elements were highly enriched in the promoter region of the GRFs in floating plants. We found that abscisic acid (ABA) is efficient at inducing the turion of Spirodela polyrhiza (giant duckweed), accompanied by the fluctuated expression of SpGRF genes in their fronds. Our results provide information about the GRF gene family in aquatic species and lay the foundation for future studies on the functions of these genes.

Characteristics of turion development in two aquatic carnivorous plants: Hormonal profiles, gas exchange and mineral nutrient content

“…As turions represent quite contrasting organs (both morphologically and physiologically) in comparison to summer growing shoot apices, it can be expected that the transition between both “stable” states shall include profound changes in the profiles of phytohormones such as CKs, auxins, and ABA in the developing shoot apices towards future turions, but also in the remaining, dying annual shoots (Adamec, 2018a; Šimura et al, 2016 ; Winston & Gorham, 1979b). The same conclusion can also be drawn from external applications of ABA or cytokinin kinetin to some aquatic plants (mainly Spirodela polyrhiza ) to induce turion formation or to revert it (Chaloupková & Smart, 1994; Smart et al, 1995; Smart & Trewavas, 1983; Weber & Noodén, 1976) and also from first genomic or transcriptomic studies on turions (Li et al, 2022; Pasaribu et al, 2023; Wang et al, 2014).…”

“…The crucial role of another phytohormone, ABA, in turion development mainly in S. polyrhiza has been known for a long time (e.g., Li et al, 2022; Smart et al, 1995; Smart & Trewavas, 1983; Wang et al, 2014; Weber & Noodén, 1976; Winston & Gorham, 1979b). Smart et al (1995) quantified ABA contents in normally growing S. polyrhiza fronds and in those induced to form turions by an exogenous ABA supply.…”

“…Similar patterns of decreasing levels of auxin and cytokinins with the central role of ABA accumulation were also found in just‐induced and developing turions of Myriophyllum verticillatum (bioassays, Weber & Noodén, 1976) and C. demersum (analyses, Best, 1979). The central role of ABA accumulation for induction of turion formation was confirmed in some species also as a result of exogenous ABA application to the growth medium (Li et al, 2022; Smart et al, 1995; Smart & Trewavas, 1983; Wang et al, 2014; Weber & Noodén, 1976), but not in summer growing C. demersum (Best, 1979). Šimura et al (2016) analyzed different cytokinins and auxins in growing apical shoot segments and mature turions of Aldrovanda vesiculosa (AV) and Utricularia australis (UA).…”