Lanthanide ions are agonists of transient gene expression in rice protoplasts and act in synergy with ABA to increase Em gene expression

Abstract

Previous work has shown that in rice suspension cells, NaCl at 0.4 M can induce Em gene expression and act synergistically with ABA, possibly by potentiating the ABA response pathway through a rate-limiting intermediate (R.M. Bostock and R.S. Quatrano (1992) Plant Physiol., 98, 1356-1363). Since calcium is an intermediate in ABA regulation of stomatal closure, we tested the effect of calcium changes on ABA-inducible Em gene expression in transiently transformed rice protoplasts. We show that calcium is required for ABA-inducible Em-GUS expression and can act in synergy with ABA. The trivalent ions lanthanum, gadolinium, and aluminum, which are known to interact with calcium- and other signaling pathways, can act at sub-millimolar concentrations to increase GUS reporter gene expression driven by several promoters in transiently transformed rice protoplasts. This effect is not specific for the ABA-inducible Em promoter, but is synergistic with ABA. The lanthanum synergy with ABA does not require calcium. In rice suspension cells, lanthanum alone does not induce Em gene expression, in contrast to transiently transformed protoplasts, yet can act synergistically with ABA to effectively increase the sensitivity to ABA greater than tenfold. Trivalent ions may be a useful tool to study the regulation of gene expression. The possible effects of trivalent ions on ABA signal transduction and gene expression are discussed.

La3+ uptake and its effect on the cytoskeleton in root protoplasts of Zea mays L.

“…The majority of studies have regarded LAN as a probe for calcium-related events in plants ( Thomson et al 1973;Pantoja et al 1992, Jackson andHall 1993;Bush 1995;Polisensky and Braam 1996;Rock and Quatrano 1996). However, the ability of low concentrations of LAN (<1 lM) to promote elongation (Fig.…”

“…Although its uptake remains controversial, LAN has been linked to intracellular processes such as inhibition of intracellular ion channels (Tester 1990), inductions of several genes (Polisensky and Braam 1996;Rock and Quatrano 1996), binding of proteins and mimicking Ca 2+ action inside the cell (Belyavskaya 1996). These effects may depend on LAN uptake, but we do not know how LAN crosses membranes, or the time course of uptake.…”

“…LAN was reported to function as a membraneimpermeable calcium antagonist (Thomson et al 1973;Pantoja et al 1992), and induces various responses including Ca 2+ -channel inhibition and Ca 2+ -related gene expression (Thomson et al 1973;Pantoja et al 1992;Jackson and Hall 1993;Bush 1995;Polisensky and Braam 1996;Rock and Quatrano 1996).…”

Drought Tolerance in Wheat

“…In wheat, protein contents of groups one, two, and three of LEA have been detected. The Em gene of wheat which encodes LEA protein first group has been vastly researched [105–107]. Group three of LEA protein has also been distinguished in seedlings of wheat [108, 109].…”

The involvement of calcium in the regulation of GPX1 expression

“…In root protoplasts of corn, La 3+ was taken up and had eVects on the cytoskeleton which is beyond its role as a Ca 2+ antagonist (Liu and Hasenstein 2005). In rice, induction of Em by La 3+ was dependent on the presence of ABA (Rock and Quatrano 1996). In Arabidopsis, various members of the TCH gene family which responded to cold shock had varied responses to the application of La 3+ , raising the possibility that the La 3+ eVect may not be related to its putative role in interfering with Ca 2+ channel activity (Polisensky and Braam 1996).…”