The evolution of abscisic acid (ABA) and ABA function in lower plants, fungi and lichen

Abstract

Abstract. Abscisic acid (ABA) -the universal stress hormone of cormophytes -was detected in very low concentrations in almost all organisms tested from a range of cyanobacteria, algae, bryophytes, fungi and lichens and higher plants (Fig. 1). There are a few reports only on stress-induced ABA biosynthesis in cyanobacteria and algae. This extra ABA is released to the external medium. Application of external ABA has been shown to produce weak and contradicting effects on development and metabolism of algae. In most studies, extremely high concentrations of external ABA have been applied, those being far beyond any physiological concentration range. It is, therefore, extremely difficult to discuss those data satisfactorily. When organisms start to colonise terrestrial habitats (e.g. aquatic liverworts, mosses), endogenous ABA is increased even under mild drought stress, then desiccation protecting mechanisms are stimulated and the formation of terrestrial organs is induced. The same can be observed in water ferns (Marsilea) and in a range of heterophyllous angiosperms. Sporophytes of hornwort and mosses that bear true stomata, have particularly high ABA levels and their stomata respond to ABA as is the case in cormophytes, although a significant regulatory function of these stomata does not exist. Fungi produce large amounts of ABA that are released into the external medium and do not seem to have a function for the fungus. Fungal ABA, however, may be significant in associations of fungi with cyanophytes and algae (lichens), in mycorrhizal associations and in the rhizosphere of higher plants.

Genetic analysis of Physcomitrella patens identifies ABSCISIC ACID NON-RESPONSIVE (ANR), a regulator of ABA responses unique to basal land plants and required for desiccation tolerance

“…However, the ABA receptor gene family is not found in the aquatic ancestors of the land plants. While ABA synthesis occurs in a wide range of basal taxa, including cyanobacteria, fungi, and algae, ABA signaling has not been convincingly detected (Hirsch et al, 1989;Kobayashi et al, 1997, Hartung, 2010 in any of these taxa.…”

The evolution of desiccation tolerance in angiosperm plants: a rare yet common phenomenon

“…Adaptive effects of drought induced ABA synthesis arose with the colonisation of the terrestrial environment by bryophytes and with the evolution of stomata and of water conducting tissue in early embryophytes (Raven 2002;Hartung 2010). ABA is pre-eminent in the angiosperms in the drought stimulation of many drought avoidance mechanisms and in the induction of desiccation tolerance in some resurrection angiosperms.…”

“…Environmental stress induces ABA production in several cyanobacteria and algae, but the concentrations of exogenous ABA required to elicit observable effects exceed normal physiological levels (Hartung 2010). Adaptive effects of drought induced ABA synthesis arose with the colonisation of the terrestrial environment by bryophytes and with the evolution of stomata and of water conducting tissue in early embryophytes (Raven 2002;Hartung 2010).…”

“…The greatest role of ABA in resurrection angiosperms is reached in the poikilochlorophyllous monocots, in which exogenous ABA induces desiccation tolerance in fully-hydrated leaves while it induces loss of their chlorophyll (Gaff and Churchill 1976). Hartung's (2010) review implies that, in the algae and cyanobacteria, any occurrence of drought-induced desiccation tolerance would probably involve non-ABA pathways. In the resurrection grass Sporobolus stapfianus jasmonate and brassinosteroids are implicated in non-ABA induction of desiccation tolerance (Ghasempour et al 2001).…”

Green Algae and the Origins of Multicellularity in the Plant Kingdom

“…Although its function in land plants is associated with the transition to terrestrial life, ABA is also produced by a wide variety of aquatic green algae, although its function in these algae is unknown (Hartung 2010). G proteincoupled receptor G proteins in plants have been linked to ABA signaling in Arabidoposis and have recently been identified in Chara, but not in any chlorophyte algae (Pandey and Assmann 2004;Hackenberg et al 2013).…”