Identification of Arabidopsis thaliana Sequences Responsive to Low Temperature and Abscisic Acid by T-DNA Tagging and in-vivo Gene Fusion

Two T-DNA tagging vectors, pMHA2 and p Delta gusBin19, were em employed for isolation of in vivo gene fusions of a promoterless gus (uidA) reporter gene to low-temperature- (LT)- and abscisic-acid- (ABA)-responsive genes or regulatory sequences (RS) of Arabidopsis thaliana. Characterization of T-2 progeny of 1200 T-DNA-tagged transgenic lines by in-situ staining of the leaf tissues for GUS activity indicated the presence of in-vivo gene fusions to constitutively expressed genes of A. thaliana in 16.1 percent of the lines (193/1200). A total of 1200 T-2 lines was tested for LT- and 841 lines for ABA-induced GUS activity, and two of these exhibited expression of the uidA reporter gene in response to these stimuli. In one of the lines (274) GUS activity was predominantly induced by LT, whereas in line 317 it was mainly responsive to ABA. The induction properties of these fusions were verified by fluorometric assay of the GUS activity and by northern analysis of the corresponding transcript. These results demonstrate that promoter trapping provides a viable alternative for identification of particular classes of plant genes or RS that respond to specific environmental stresses; e.g., low temperature, drought, insect injuries and pathogen attack, or that are regulated hormonally or developmentally.