75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

241 rcd3 mutation disrupts abscisic acid, reactive oxygen species and nitric oxide induced
stomatal closure in Arabidopsis mutation disrupts abscisic acid, reactive oxygen species
and nitric oxide induced stomatal closure in Arabidopsis
Triin Kollist
University of Tartu
Ozone (O 3 ), the predominant air pollutant, has been shown to be a useful tool to induce acute formation of reactive
oxygen species (ROS) and to identify molecular components regulating ROS induced processes in leaf cells. We have
previously identified a series of O3-sensitive rcd (for radical induced cell death) mutants. Here we describe rcd3 which
phenotype is related with stomatal function. rcd3 has constitutively higher stomatal conductance than the Col-0 wild type.
Also O3-induced stomatal closure is largely suppressed in rcd3. The number of stomata in the abaxial side of the leaf is
not altered. Detailed analysis of stomatal responses right after the onset of O3-treatment revealed that O3 induces a rapid
stomatal closure and subsequent reopening within 30 minutes in most of the mutants and ecotypes including Col-0 and
Ler. Interestingly, in the abscisic acid (ABA) insensitive mutant’s abi1, abi2, ost1 and in rcd3, the transient closure was
absent. The phenotype of rcd3 is not caused by altered ABA content since a six hour treatment with O3 caused similar
ABA induction in both Col-0 and rcd3. However, guard cells of rcd3 are insensitive to ABA, hydrogen peroxide and
nitric oxide treatment measured as reduction of stomatal aperture. It is likely that map-based cloning of rcd3, currently
underway, will reveal a new regulator for the signal transduction pathway leading to stomatal closure.
242 Reciprocal leaf and root response to nitrogen stress in Arabidopsis thaliana
Cawas Engineer, Robert Kranz
Washington University in St. Louis
Nitrogen is an essential macronutrient for plant growth and survival. We analyzed the temporal and spatial onset
of nitrogen stress sensing in Arabidopsis using the promoter of a high affinity ammonium transporter, AtAmt1.1. An
AtAmt1.1-Gal4 driver line with three 5XUAS reporters (LUC, GFP, and GUS) facilitated the in vivo profiling of the
whole plant and individual cells throughout the plant. The gene is expressed in the roots only under nitrogen stress and
only in the leaves under nitrogen sufficient conditions. This thirty-five fold reciprocal expression indicates that Arabidopsis
undergoes rapid resource reallocation in plants grown under different nitrogen supply regimens. Ultimately, nitrogen
stress-mediated reallocation results in root architectural restructuring. The GFP and GUS reporters facilitated the temporal
and spatial analyses within the cell types of root and aerial tissues. We propose a model for the precise timing of this
nitrogen stress response from the perspective of AtAmt1.1-expression profiling.