ABSTRACT
Treating Arabidopsis roots with exogenous auxin results in dramatic changes in cellular processes including de novo induction of lateral roots which later emerge through the overlying cells. Microarray experiments reveal approximately 80 genes that are substantially up-regulated in the root over the first 12 h following auxin treatment. We hypothesize that the observed increase in expression of pectate lyase family genes leads to degradation of the pectin-rich middle lamellae, allowing cells in the parent root to separate cleanly. Differences in the degree of pectin methylation in lateral and parent roots may explain why lateral roots are not degraded themselves.
Subject(s)
Arabidopsis/growth & development , Arabidopsis/genetics , Gene Expression Profiling , Gene Expression Regulation, Plant/genetics , Indoleacetic Acids/pharmacology , Plant Roots/growth & development , Arabidopsis/physiology , Arabidopsis Proteins/analysis , Arabidopsis Proteins/genetics , Arabidopsis Proteins/physiology , Cell Wall/drug effects , Cell Wall/physiology , DNA, Plant/analysis , DNA, Plant/genetics , Gene Expression Regulation, Plant/drug effects , Gene Expression Regulation, Plant/physiology , Genes, Plant/genetics , Genes, Plant/physiology , Methylation , Oligonucleotide Array Sequence Analysis , Phospholipases A/analysis , Phospholipases A/genetics , Phospholipases A/physiology , Plant Roots/chemistry , Plant Roots/drug effects , Polysaccharide-Lyases/analysis , Polysaccharide-Lyases/genetics , Polysaccharide-Lyases/physiologyABSTRACT
Fungi must recognize plant-specific signals to initiate subsequent morphogenetic events such as filamentation that lead to infection. Here we show that the plant hormone indoleacetic acid (IAA) induces adhesion and filamentation of Saccharomyces cerevisiae. Genome expression profiling of cells treated with IAA identified Yap1, a fungal specific transcription factor, as a key mediator of this response. Strains lacking YAP1 (yap1-1) are hypersensitive to growth on IAA because they accumulate more IAA than can wild type. Members of a family of transporters the amino acid/auxin:proton symport permeases with homology to AUX1, a putative IAA transporter from plants, are up-regulated in the yap1-1 mutant. Deletion of any one of these transporters makes yap1-1 mutants more resistant to IAA by decreasing its uptake. The permease mutants are defective in IAA perception and filamentation. The ability of a fungus to perceive a plant hormone that causes it to differentiate into an invasive form has important implications for plant-pathogen interactions.
