title: Global analysis of della direct targets in early gibberellin signaling in Arabidopsis.
abstract: Bioactive gibberellins (GAs) are phytohormones that regulate growth and development throughout the life cycle of plants. DELLA proteins are conserved growth repressors that modulate all aspects of GA responses. These GA-signaling repressors are nuclear localized and likely function as transcriptional regulators. Recent studies demonstrated that GA, upon binding to its receptor, derepresses its signaling pathway by binding directly to DELLA proteins and targeting them for rapid degradation via the ubiquitin-proteasome pathway. Therefore, elucidating the signaling events immediately downstream of DELLA is key to our understanding of how GA controls plant development. Two sets of microarray studies followed by quantitative RT-PCR analysis allowed us to identify 14 early GA-responsive genes that are also early DELLA-responsive in Arabidopsis thaliana seedlings. Chromatin immunoprecipitation provided evidence for in vivo association of DELLA with promoters of eight of these putative DELLA target genes. Expression of all 14 genes was downregulated by GA and upregulated by DELLA. Our study reveals that DELLA proteins play two important roles in GA signaling: (1) they help establish GA homeostasis by direct feedback regulation on the expression of GA biosynthetic and GA receptor genes, and (2) they promote the expression of downstream negative components that are putative transcription factors/regulators or ubiquitin E2/E3 enzymes. In addition, one of the putative DELLA targets, XERICO, promotes accumulation of abscisic acid (ABA) that antagonizes GA effects. Therefore, DELLA may restrict GA-promoted processes by modulating both GA and ABA pathways.
authors.affiliation: Department of Biology, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Zentella
authors.forename: Zhong-Lin
authors.initials: ZL
authors.lastname: Zhang
authors.forename: Mehea
authors.initials: M
authors.lastname: Park
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Thomas
authors.forename: Akira
authors.initials: A
authors.lastname: Endo
authors.forename: Kohji
authors.initials: K
authors.lastname: Murase
authors.forename: Christine M
authors.initials: CM
authors.lastname: Fleet
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Jikumaru
authors.forename: Eiji
authors.initials: E
authors.lastname: Nambara
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Tai-Ping
authors.initials: TP
authors.lastname: Sun
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005875:Gibberellins / Q000494:pharmacology*; D015151:Immunoblotting; D008954:Models, Biological; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010937:Plant Growth Regulators / Q000494:pharmacology; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D005875:Gibberellins; D010937:Plant Growth Regulators; C508468:RGA protein, Arabidopsis; D012097:Repressor Proteins; C513943:XERICO protein, Arabidopsis; D000040:Abscisic Acid