Indole‐3‐acetic acid uptake in isolated protoplasts of the moss Funaria hygrometrica

Abstract

Protoplasts of the moss Funaria hygrometrica Hedw were used to study the mechanism of Indole‐3‐acetic acid (IAA) accumulation. Three main components appeared to be involved. 1. The pH gradient between plasma and outer medium is the basis for an anion trap. The protonophores carbonylcyanide m‐chlorophenylhydrazone (CCCP) and carbonylcyanide p–trifluoromethoxyphenylhydrazone (FCCP) reduce IAA accumulation by destruction of the pH gradient. 2 An intact efflux carrier could be demonstrated by an increase of IAA accumulation with the efflux inhibitors 2,3,5–trüodo‐benzoic acid (TIBA) and 1‐naphthy‐phthalamic acid (NPA). In efflux experiments, reduction of IAA efflux by the two inhibitors was directly demonstrated. 3. The existence of an influx carrier was concluded from the strong stimulation of IAA accumulation by calcium in calcium‐deprived protoplasts. It is postulated that this carrier system transports IAA anions, protons and Ca2+. A computer simulation of the accumulation process with the three components, including internal IAA concentration determined by enzyme‐linked immunosorbent assay (ELISA), gave a highly accurate description of the data measured in the different experiments.

Primitive Auxin Response without TIR1 and Aux/IAA in the Charophyte Alga Klebsormidium nitens

“…Among basal land plants, e.g. the moss Funaria hygrometrica, TIBA inhibits IAA efflux from protonema and rhizoids and increases IAA accumulation in protoplasts (Geier et al, 1990). Therefore, we also measured cell division and cell elongation in the presence of 100 mM TIBA.…”

Homologues of the Arabidopsis thaliana SHI/STY/LRP1 genes control auxin biosynthesis and affect growth and development in the moss Physcomitrella patens

“…Whereas some studies have reported that PAT inhibitors have effects on gametophyte development (Geier et al, 1990;Schwuchow et al, 2001), a recent study of five different mosses suggested that long-range PAT occurs in the subordinate sporophyte generation, but not in the gametophyte leafy shoot (Fujita et al, 2008). Consequently, it appears likely that tightly controlled local auxin biosynthesis is important in mosses, and that increased knowledge about these processes could shed light on the ancestral mechanisms for creation of auxin maxima in plants.…”