Poster: Signaling, cell-to-cell

Abs # 443: Stress-induced elevation of arginine decarboxylase occurs via two distinct signal transduction pathways

Presenter:	Feirer, Russ P., russ.feirer@snc.edu
Authors	Feirer, Russ P. (A)   St. John, Bonnie R. (A)   Gapinski, Julie M. (A)   Kerswill, Heather M. (A)
Affiliations:	(A): Biology Department, St Norbert College

Polyamines and the enzymes responsible for their biosynthesis exhibit elevations during a number of developmental and physiological processes. Arginine decarboxylase (ADC), a key enzyme in one of two alternate pathways leading to putrescine production, appears to be important in the response of plants to many abiotic stresses. Elevations of this enzyme are observed during osmotic stress and, not unexpectedly, upon treatment with abscisic acid (ABA), a plant growth regulator integral to a plant’s response to water loss. Both exogenously applied ABA and osmotic stress led to increased ADC activity in Arabidopsis thaliana grown in vitro. Osmotic stress caused elevations of ADC activity in ABA-deficient and ABA-insensitive mutant Arabidopsis, which suggests that more than one signal transduction pathway may control the expression of this enzyme. Lanthanum chloride, a calcium ion channel blocker, was found to partially reduce but not completely block the elevation of ADC due to both ABA and osmotic stress. Phenylarsine oxide, an inhibitor of the type 2C protein phosphatase involved in the ABA signal transduction pathway, blocked the induction of ADC by ABA, but only partially reduced the response to osmotic stress. Administration of hydrogen peroxide, a component in the pathway mediating the response to ABA, was also found to induce ADC activity in the in vitro grown Arabidopsis. These findings suggest that the induction of ADC can occur via ABA-dependent and ABA-independent pathways.