title: Differential effects of the peptides Stomagen, EPF1 and EPF2 on activation of MAP kinase MPK6 and the SPCH protein level.
abstract: The positioning and density of leaf stomata are regulated by three secretory peptides, EPIDERMAL PATTERNING FACTOR 1 (EPF1), EPF2 and stomagen. Several lines of published evidence have suggested a regulatory pathway as follows. EPF1 and EPF2 are perceived by receptor complexes consisting of a receptor-like protein, TOO MANY MOUTHS (TMM), and receptor kinases, ERECTA (ER), ERECTA-LIKE (ERL) 1 and ERL2. These receptors activate a mitogen-activated protein (MAP) kinase module. MAP kinases phosphorylate and destabilize the transcription factor SPEECHLESS (SPCH), resulting in a decrease in the number of stomatal lineage cells. Stomagen acts antagonistically to EPF1 and EPF2. However, there is no direct evidence that EPF1 and EPF2 activate or that stomagen inactivates the MAP kinase cascade, through which they might regulate the SPCH level. Experimental modulation of these peptides in Arabidopsis thaliana would change the number of stomatal lineage cells in developing leaves, which in turn would change the expression of SPCH, making the interpretation difficult. Here we reconstructed this signaling pathway in differentiated leaf cells of Nicotiana benthamiana to examine signaling without the confounding effect of cell type change. We show that EPF1 and EPF2 are able to activate the MAP kinase MPK6, and that both EPF1 and EPF2 are able to decrease the SPCH level, whereas stomagen is able to increase it. Our data also suggest that EPF1 can be recognized by TMM together with any ER family receptor kinase, whereas EPF2 can be recognized by TMM together with ERL1 or ERL2, but not by TMM together with ER.
authors.affiliation: Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Pawan Kumar
authors.initials: PK
authors.lastname: Jewaria
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hara
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tanaka
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kondo
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Betsuyaku
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Sawa
authors.forename: Youji
authors.initials: Y
authors.lastname: Sakagami
authors.forename: Saburo
authors.initials: S
authors.lastname: Aimoto
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Kakimoto
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D019070:Cell Lineage; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D010766:Phosphorylation; D019441:Plant Epidermis / Q000166:cytology / Q000235:genetics / Q000502:physiology; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000502:physiology; D054046:Plant Stomata / Q000166:cytology / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D020928:Mitogen-Activated Protein Kinases; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C547253:EPF1 protein, Arabidopsis; C542689:EPF2 protein, Arabidopsis; C517480:SPEECHLESS protein, Arabidopsis; C547254:Stomagen protein, Arabidopsis; C436293:MPK6 protein, Arabidopsis
keywords: Arabidopsis thaliana; EPF; MAP kinase; Nicotiana benthamiana; SPEECHLESS; Stomata