Brassinosteroid regulates stomatal development by GSK3-mediated inhibition of a MAPK pathway.
Plants must coordinate the regulation of biochemistry and anatomy to optimize photosynthesis and water-use efficiency. The formation of stomata, epidermal pores that facilitate gas exchange, is highly coordinated with other aspects of photosynthetic development. The signalling pathways controlling stomata development are not fully understood, although mitogen-activated protein kinase (MAPK) signalling is known to have key roles. Here we demonstrate in Arabidopsis that brassinosteroid regulates stomatal development by activating the MAPK kinase kinase (MAPKKK) YDA (also known as YODA). Genetic analyses indicate that receptor kinase-mediated brassinosteroid signalling inhibits stomatal development through the glycogen synthase kinase 3 (GSK3)-like kinase BIN2, and BIN2 acts upstream of YDA but downstream of the ERECTA family of receptor kinases. Complementary in vitro and in vivo assays show that BIN2 phosphorylates YDA to inhibit YDA phosphorylation of its substrate MKK4, and that activities of downstream MAPKs are reduced in brassinosteroid-deficient mutants but increased by treatment with either brassinosteroid or GSK3-kinase inhibitor. Our results indicate that brassinosteroid inhibits stomatal development by alleviating GSK3-mediated inhibition of this MAPK module, providing two key links; that of a plant MAPKKK to its upstream regulators and of brassinosteroid to a specific developmental output.
Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305-4150, USA.
Tae-Wuk
TW
Kim
Marta
M
Michniewicz
Dominique C
DC
Bergmann
Zhi-Yong
ZY
Wang
D017360:Arabidopsis / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D060406:Brassinosteroids / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054046:Plant Stomata / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana
D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D038362:Glycogen Synthase Kinase 3; D020930:MAP Kinase Kinase Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011956:Receptors, Cell Surface; C459090:too many mouths protein, Arabidopsis; C448985:At4g18710 protein, Arabidopsis; C457763:ER protein, Arabidopsis; C481302:YODA protein, Arabidopsis; C519871:MKK4 protein, Arabidopsis