title: Hypocotyl transcriptome reveals auxin regulation of growth-promoting genes through GA-dependent and -independent pathways.
abstract: Many processes critical to plant growth and development are regulated by the hormone auxin. Auxin responses are initiated through activation of a transcriptional response mediated by the TIR1/AFB family of F-box protein auxin receptors as well as the AUX/IAA and ARF families of transcriptional regulators. However, there is little information on how auxin regulates a specific cellular response. To begin to address this question, we have focused on auxin regulation of cell expansion in the Arabidopsis hypocotyl. We show that auxin-mediated hypocotyl elongation is dependent upon the TIR1/AFB family of auxin receptors and degradation of AUX/IAA repressors. We also use microarray studies of elongating hypocotyls to show that a number of growth-associated processes are activated by auxin including gibberellin biosynthesis, cell wall reorganization and biogenesis, and others. Our studies indicate that GA biosynthesis is required for normal response to auxin in the hypocotyl but that the overall transcriptional auxin output consists of PIF-dependent and -independent genes. We propose that auxin acts independently from and interdependently with PIF and GA pathways to regulate expression of growth-associated genes in cell expansion.
authors.affiliation: Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Elisabeth J
authors.initials: EJ
authors.lastname: Chapman
authors.forename: Kathleen
authors.initials: K
authors.lastname: Greenham
authors.forename: Cristina
authors.initials: C
authors.lastname: Castillejo
authors.forename: Ryan
authors.initials: R
authors.lastname: Sartor
authors.forename: Agniezska
authors.initials: A
authors.lastname: Bialy
authors.forename: Tai-Ping
authors.initials: TP
authors.lastname: Sun
authors.forename: Mark
authors.initials: M
authors.lastname: Estelle
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development*; D007210:Indoleacetic Acids / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D044783:F-Box Proteins; D007210:Indoleacetic Acids; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C501405:TIR1 protein, Arabidopsis; C046131:auxin receptor, plant