title: An abscisic acid inducible Arabidopsis MAPKKK, MAPKKK18 regulates leaf senescence via its kinase activity.
abstract: Abscisic acid (ABA) is a phytohormone that regulates many physiological functions, such as plant growth, development and stress responses. The MAPK cascade plays an important role in ABA signal transduction. Several MAPK and MAPKK molecules are reported to function in ABA signaling; however, there have been few studies related to the identification of MAPKKK upstream of MAPKK in ABA signaling. In this study, we show that an Arabidopsis MAPKKK, MAPKKK18 functions in ABA signaling. The expression of MAPKKK18 was induced by ABA treatment. Yeast two-hybrid analysis revealed that MAPKKKK18 interacted with MKK3, which interacted with C-group MAPK, MPK1/2/7. Immunoprecipitated kinase assay showed that the 3xFlag-tagged MAPKKK18, expressed in Arabidopsis plants, was activated when treated with ABA. These results indicate the possibility that the MAPK cascade is composed of MAPKKK18, MKK3 and MPK1/2/7 in ABA signaling. The transgenic plants overexpressing MAPKKK18 (35S:MAPKKK18) and its kinase negative mutant (35S:MAPKKK18 KN) were generated, and their growth was monitored. Compared with the WT plant, 35S:MAPKKK18 and 35S:MAPKKK18 KN showed smaller and bigger phenotypes, respectively. Senescence of the rosette leaves was promoted in 35S:MAPKKK18, but suppressed in 35S:MAPKKK18 KN. Furthermore, ABA-induced leaf senescence was accelerated in 35S:MAPKKK18. These results suggest that MAPKKK18 controls the plant growth by adjusting the timing of senescence via its protein kinase activity in ABA dependent manners.
authors: Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo, 657-8501, Japan, matsuoka@people.kobe-u.ac.jp.
authors: Daisuke
authors: D
authors: Matsuoka
authors: Takuto
authors: T
authors: Yasufuku
authors: Tomoyuki
authors: T
authors: Furuya
authors: Takashi
authors: T
authors: Nanmori
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D020930:MAP Kinase Kinase Kinases / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D010937:Plant Growth Regulators / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D011994:Recombinant Proteins; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D012639:Seeds / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D013312:Stress, Physiological; D013997:Time Factors; D020798:Two-Hybrid System Techniques; D014867:Water / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D010937:Plant Growth Regulators; D011994:Recombinant Proteins; D014867:Water; D000040:Abscisic Acid; D020930:MAP Kinase Kinase Kinases; C000598433:MAPKKK18 protein, Arabidopsis