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BSK s are partially redundant positive regulators of brassinosteroid signaling in A rabidopsis
Author(s) -
Sreeramulu Shivakumar,
Mostizky Yana,
Sunitha Sukumaran,
Shani Eilon,
Nahum Hadas,
Salomon Dor,
Hayun Liat Ben,
Gruetter Christian,
Rauh Daniel,
Ori Naomi,
Sessa Guido
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12175
Subject(s) - brassinosteroid , kinase , mutant , signal transduction , microbiology and biotechnology , arabidopsis thaliana , phosphorylation , biology , arabidopsis , brassinolide , gene , biochemistry , botany , plant growth
Summary Arabidopsis thaliana brassinosteroid signaling kinases ( BSK s) constitute a receptor‐like cytoplasmic kinase sub‐family ( RLCK ‐ XII ) with 12 members. Previous analysis demonstrated a positive role for BSK 1 and BSK 3 in the initial steps of brassinosteroid ( BR ) signal transduction. To investigate the function of BSK s in plant growth and BR signaling, we characterized T‐ DNA insertion lines for eight BSK genes ( BSK 1– BSK 8 ) 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 BSK s interacted in vivo with the BR receptor BRI 1, and served as its phosphorylation substrates in vitro . The BIN 2 and BIL 2 GSK 3‐like kinases, which are negative regulators of BR signaling, interacted in vivo with BSK s and phosphorylated them in vitro , probably at different sites to BRI 1. This study demonstrates redundant biological functions for BSK s, and suggests the existence of a regulatory link between BSK s and GSK 3‐like kinases.