Venus Flytrap HKT1-Type Channel Provides for Prey Sodium Uptake into Carnivorous Plant Without Conflicting with Electrical Excitability

Abstract

The animal diet of the carnivorous Venus flytrap, Dionaea muscipula, contains a sodium load that enters the capture organ via an HKT1-type sodium channel, expressed in special epithelia cells on the inner trap lobe surface. DmHKT1 expression and sodium uptake activity is induced upon prey contact. Here, we analyzed the HKT1 properties required for prey sodium osmolyte management of carnivorous Dionaea. Analyses were based on homology modeling, generation of model-derived point mutants, and their functional testing in Xenopus oocytes. We showed that the wild-type HKT1 and its Na+- and K+-permeable mutants function as ion channels rather than K+ transporters driven by proton or sodium gradients. These structural and biophysical features of a high-capacity, Na+-selective ion channel enable Dionaea glands to manage prey-derived sodium loads without confounding the action potential-based information management of the flytrap.

Venus flytrap carnivorous lifestyle builds on herbivore defense strategies

“…In the flytrap, a captured insect struggling to escape or COR treatment alone both activate the JA pathway ( Fig. 4; Escalante-Perez et al 2011;Böhm et al 2016a). Activation of the JA pathway leads to the processing and consumption of, from the view of a noncarnivorous plant, a potential herbivore.…”

“…Most likely, sodium ions are required for osmotic adjustment. In contrast to K + , however, Na + accumulates only in mature traps (Böhm et al 2016a) and is not channeled to young ones, presumably to protect young traps from its toxic effect during organ growth and development. In summary, our work extends and refines the current model of the Dionaea hunting cycle.…”

Chemical Composition of Spring Rapeseed Grown in Copper- Contaminated Soil Amended With Halloysite and Zeolite

“…Sodium concentrations vary considerably in plants. Sodium and potassium have similar properties, and they exert complementary effects on crop yield [Böhm et al, 2016]. In this experiment, the addition of copper and mineral adsorbents had a minor influence on the sodium content of the aerial parts of spring rapeseed plants (Figure 3).…”

Revealing mechanisms of salinity tissue tolerance in succulent halophytes: A case study for Carpobrotus rossi

“…Initially defined as the high affinity potassium transporter (hence, the abbreviation), the HKT family is now divided into two distinct subfamilies based on their transport selectivity (Platten et al, ), and it was shown that the essential feature for strict Na + selectivity was the presence of the serine residue in their first pore loop (Böhm et al, ). In the contrast, K + ‐permeable HKT1 transporters frequently have a glycine in the respective position (Böhm et al, ). It was shown that in Arabidopsis roots HKT1 showed no sensitivity to external Ca 2+ (Rus et al, ; Tyerman & Skerrett, ).…”