title: Calcium-dependent protein kinase CPK28 targets the methionine adenosyltransferases for degradation by the 26S proteasome and affects ethylene biosynthesis and lignin deposition in Arabidopsis.
abstract: S-adenosylmethionine (AdoMet) is synthesized by methionine adenosyltransferase (MAT), and plays an essential role in ethylene biosynthesis and other methylation reactions. Despite increasing knowledge of MAT regulation at transcriptional levels, how MAT is post-translationally regulated remains unknown in plant cells. Phosphorylation is an important post-translational modification for regulating the activity of enzymes, protein function and signaling transduction. Using molecular and biochemical approaches, we have identified the phosphorylation of MAT proteins by calcium-dependent protein kinase (CPK28). Phenotypically, both MAT2-overexpressing transgenic plants and cpk28 mutants display short hypocotyls and ectopic lignifications. Their shortened hypocotyl phenotypes are caused by ethylene overproduction and rescued by ethylene biosynthesis inhibitor aminoethoxyvinylglycine treatment. Genetic evidence reveals that MAT2 mutation restores the phenotype of ectopic lignification in CPK28-deficient plants. We find that total MAT proteins and AdoMet are increased in cpk28 mutants, but decreased in CPK28-overexpressing seedlings. We also find that MATs in OE::CPK28 are degraded through the 26S proteasome pathway. Our work suggests that CPK28 targets MATs (MAT1, MAT2 and MAT3) for degradation by the 26S proteasome pathway, and thus affects ethylene biosynthesis and lignin deposition in Arabidopsis.
authors.affiliation: School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China.
authors.forename: Nenghui
authors.initials: N
authors.lastname: Ye
authors.affiliation: Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China.
authors.forename: Fuyuan
authors.initials: F
authors.lastname: Zhu
authors.affiliation: School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
authors.forename: Haoxuan
authors.initials: H
authors.lastname: Li
authors.affiliation: School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.affiliation: School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
authors.forename: Liwen
authors.initials: L
authors.lastname: Jiang
authors.affiliation: School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China.|Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D005030:Ethylenes / Q000096:biosynthesis*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D008031:Lignin / Q000378:metabolism*; D008716:Methionine Adenosyltransferase / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000235:genetics / Q000502:physiology; D017871:Calcium-Calmodulin-Dependent Protein Kinases
chemical_list: D029681:Arabidopsis Proteins; D005030:Ethylenes; D008031:Lignin; D008716:Methionine Adenosyltransferase; D046988:Proteasome Endopeptidase Complex; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C036216:ethylene; C061553:ATP dependent 26S protease
keywords: 26S proteasome; calcium-dependent protein kinase 28; ethylene; lignification; methionine adenosyltransferase; post-translational modification