title: ABI3 and PIL5 collaboratively activate the expression of SOMNUS by directly binding to its promoter in imbibed Arabidopsis seeds.
abstract: A previous study showed that SOMNUS (SOM), which encodes a C3H-type zinc finger protein, is a key negative regulator of seed germination that acts downstream of PHYTOCHROME INTERACTING FACTOR3-LIKE5 (PIL5). However, it was not determined if PIL5 is the sole regulator of SOM expression. Public microarray data suggest that the expression of SOM mRNA is regulated also by ABSCISIC ACID INSENSITIVE3 (ABI3), another key regulator of seed germination. By analyzing abi3 mutants and ABI3 overexpression lines, we show here that ABI3 activates the expression of SOM mRNA collaboratively with PIL5 in imbibed seeds. Chromatin immunoprecipitation analysis coupled with electrophoretic mobility shift assay indicate that ABI3 activates the expression of SOM mRNA by directly binding to two RY motifs present in the SOM promoter in vivo, which is further supported by the greatly decreased expression of a reporter gene driven by a SOM promoter bearing mutated RY motifs. At the protein level, the ABI3 protein interacts with the PIL5 protein. The ABI3-PIL5 interaction, however, does not affect targeting of ABI3 and PIL5 to SOM promoters. Taken together, our results indicate that ABI3 and PIL5 collaboratively activate the expression of SOM mRNA by directly binding to and interacting with each other at the SOM promoter.
authors.affiliation: Department of Biological Sciences, KAIST, Daejeon 305-701, Korea.
authors.forename: Jeongmoo
authors.initials: J
authors.lastname: Park
authors.forename: Nayoung
authors.initials: N
authors.lastname: Lee
authors.forename: Woohyun
authors.initials: W
authors.lastname: Kim
authors.forename: Soohwan
authors.initials: S
authors.lastname: Lim
authors.forename: Giltsu
authors.initials: G
authors.lastname: Choi
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D008027:Light; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics* / Q000528:radiation effects; D014157:Transcription Factors
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002352:Carrier Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C091601:ABI3 protein, Arabidopsis; C533360:SOMNUS protein, Arabidopsis; C508068:At2g20180 protein, Arabidopsis