title: Identification of MEDIATOR16 as the Arabidopsis COBRA suppressor MONGOOSE1.
abstract: We performed a screen for genetic suppressors of cobra, an Arabidopsis mutant with defects in cellulose formation and an increased ratio of unesterified/esterified pectin. We identified a suppressor named mongoose1 (mon1) that suppressed the growth defects of cobra, partially restored cellulose levels, and restored the esterification ratio of pectin to wild-type levels. mon1 was mapped to the MEDIATOR16 (MED16) locus, a tail mediator subunit, also known as SENSITIVE TO FREEZING6 (SFR6). When separated from the cobra mutation, mutations in MED16 caused resistance to cellulose biosynthesis inhibitors, consistent with their ability to suppress the cobra cellulose deficiency. Transcriptome analysis revealed that a number of cell wall genes are misregulated in med16 mutants. Two of these genes encode pectin methylesterase inhibitors, which, when ectopically expressed, partially suppressed the cobra phenotype. This suggests that cellulose biosynthesis can be affected by the esterification levels of pectin, possibly through modifying cell wall integrity or the interaction of pectin and cellulose.
authors.affiliation: Energy Biosciences Institute, University of California, Berkeley, CA 94720; Plant and Microbial Biology Department, University of California, Berkeley, CA 94720;
authors.forename: Nadav
authors.initials: N
authors.lastname: Sorek
authors.affiliation: Energy Biosciences Institute, University of California, Berkeley, CA 94720;
authors.forename: Heidi
authors.initials: H
authors.lastname: Szemenyei
authors.affiliation: Energy Biosciences Institute, University of California, Berkeley, CA 94720;
authors.forename: Hagit
authors.initials: H
authors.lastname: Sorek
authors.affiliation: Energy Biosciences Institute, University of California, Berkeley, CA 94720;
authors.forename: Abigail
authors.initials: A
authors.lastname: Landers
authors.affiliation: School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom;
authors.forename: Heather
authors.initials: H
authors.lastname: Knight
authors.affiliation: Energy Biosciences Institute, University of California, Berkeley, CA 94720;
authors.forename: Stefan
authors.initials: S
authors.lastname: Bauer
authors.affiliation: Department of Chemistry, University of California, Berkeley, CA 94720.
authors.forename: David E
authors.initials: DE
authors.lastname: Wemmer
authors.affiliation: Energy Biosciences Institute, University of California, Berkeley, CA 94720; Plant and Microbial Biology Department, University of California, Berkeley, CA 94720; crs@berkeley.edu.
authors.forename: Chris R
authors.initials: CR
authors.lastname: Somerville
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D002482:Cellulose / Q000032:analysis / Q000096:biosynthesis; D004951:Esterification; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D009005:Monosaccharides / Q000032:analysis / Q000378:metabolism; D009154:Mutation; D010368:Pectins / Q000378:metabolism; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C427475:COB protein, Arabidopsis; D008562:Membrane Glycoproteins; D009005:Monosaccharides; C575423:SFR6 protein, Arabidopsis; D015534:Trans-Activators; D010368:Pectins; D002482:Cellulose
keywords: cell wall; cellulose; freezing tolerance; pectin; transcription