title: BSKs are partially redundant positive regulators of brassinosteroid signaling in Arabidopsis.
abstract: Arabidopsis thaliana brassinosteroid signaling kinases (BSKs) constitute a receptor-like cytoplasmic kinase sub-family (RLCK-XII) with 12 members. Previous analysis demonstrated a positive role for BSK1 and BSK3 in the initial steps of brassinosteroid (BR) signal transduction. To investigate the function of BSKs in plant growth and BR signaling, we characterized T-DNA insertion lines for eight BSK genes (BSK1-BSK8) and multiple mutant combinations. Simultaneous elimination of three BSK genes caused alterations in growth and the BR response, and the most severe phenotypes were observed in the bsk3,4,7,8 quadruple and bsk3,4,6,7,8 pentuple mutants, which displayed reduced rosette size, leaf curling and enhanced leaf inclination. In addition, upon treatment with 24-epibrassinolide, these mutants showed reduced hypocotyl elongation, enhanced root growth and alteration in the expression of BR-responsive genes. Some mutant combinations also showed antagonistic interactions. In support of a redundant function in BR signaling, multiple BSKs interacted in vivo with the BR receptor BRI1, and served as its phosphorylation substrates in vitro. The BIN2 and BIL2 GSK3-like kinases, which are negative regulators of BR signaling, interacted in vivo with BSKs and phosphorylated them in vitro, probably at different sites to BRI1. This study demonstrates redundant biological functions for BSKs, and suggests the existence of a regulatory link between BSKs and GSK3-like kinases.
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv, 69978, Israel.
authors.forename: Shivakumar
authors.initials: S
authors.lastname: Sreeramulu
authors.forename: Yana
authors.initials: Y
authors.lastname: Mostizky
authors.forename: Sukumaran
authors.initials: S
authors.lastname: Sunitha
authors.forename: Eilon
authors.initials: E
authors.lastname: Shani
authors.forename: Hadas
authors.initials: H
authors.lastname: Nahum
authors.forename: Dor
authors.initials: D
authors.lastname: Salomon
authors.forename: Liat Ben
authors.initials: LB
authors.lastname: Hayun
authors.forename: Christian
authors.initials: C
authors.lastname: Gruetter
authors.forename: Daniel
authors.initials: D
authors.lastname: Rauh
authors.forename: Naomi
authors.initials: N
authors.lastname: Ori
authors.forename: Guido
authors.initials: G
authors.lastname: Sessa
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060406:Brassinosteroids / Q000378:metabolism* / Q000494:pharmacology; D035264:Flowers / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D010766:Phosphorylation; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D013260:Steroids, Heterocyclic / Q000378:metabolism* / Q000494:pharmacology; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D010937:Plant Growth Regulators; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D013260:Steroids, Heterocyclic; C448985:At4g18710 protein, Arabidopsis; C108270:BRI1 protein, Arabidopsis; C023623:brassinolide