title: The ABSCISIC ACID INSENSITIVE 3 (ABI3) gene is modulated by farnesylation and is involved in auxin signaling and lateral root development in Arabidopsis.
abstract: Genetic screens have identified a number of genes that regulate abscisic acid (ABA) responsiveness in Arabidopsis. Using a combination of suppressor screens and double mutant analysis, we have determined a genetic relationship for a number of these ABA response loci. Based on germination in the presence of exogenous ABA, the ABI1 and ABI2 phosphatases act at or upstream of the ERA1 farnesyl transferase and the ABI3 and ABI5 transcription factors act at or downstream of ERA1. In contrast with ABI3 and ABI5, the ABI4 transcription factor appears to act at or upstream of ERA1. Based on reporter gene constructs, the upstream regulation of ABI3 by ERA1 occurs at least partially at the level of transcription, suggesting that this lipid modification is required to attenuate ABI3 expression. Similar experiments also indicate that ABI3 is auxin inducible in lateral root primordia. Related to this, loss-of-function abi3 alleles show reduced lateral root responsiveness in the presence of auxin and an auxin transport inhibitor, and era1 mutants have increased numbers of lateral roots. These results suggest the possibility that genes identified through ABA responsive germination screens such as ERA1 and ABI3 have functions in auxin action in Arabidopsis.
authors.affiliation: Department of Botany, University of Toronto, 25 Willcocks St, Toronto, Canada M5S 3B2.
authors.forename: Siobhan Mary
authors.initials: SM
authors.lastname: Brady
authors.forename: Sara F
authors.initials: SF
authors.lastname: Sarkar
authors.forename: Dario
authors.initials: D
authors.lastname: Bonetta
authors.forename: Peter
authors.initials: P
authors.lastname: McCourt
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018525:Germination / Q000187:drug effects; D007210:Indoleacetic Acids / Q000494:pharmacology*; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D017368:Protein Prenylation; D015398:Signal Transduction / Q000187:drug effects*; D014157:Transcription Factors
chemical_list: C091601:ABI3 protein, Arabidopsis; D029681:Arabidopsis Proteins; C411293:ERA1 protein, Arabidopsis; D007210:Indoleacetic Acids; D014157:Transcription Factors; D000040:Abscisic Acid