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Title: Mutation of Mediator subunit $CDK$ counteracts the stunted growth and salicylic acid hyperaccumulation phenotypes of an Arabidopsis $MED$ mutant

Abstract

The Mediator complex functions as a hub for transcriptional regulation. MED5, an Arabidopsis Mediator tail subunit, is required for maintaining phenylpropanoid homeostasis. A semidominant mutation (ref4-3) that causes a single amino acid substitution in MED5b functions as a strong suppressor of the pathway, leading to decreased soluble phenylpropanoid accumulation, reduced lignin content and dwarfism. By contrast, loss of MED5 results in increased concentrations of phenylpropanoids. We used a reverse genetic approach to identify suppressors of ref4-3 and found that ref4-3 requires CDK8, a kinase module subunit of Mediator, to repress plant growth. The genetic interaction between MED5 and CDK8 was further characterized using mRNA-sequencing (RNA-seq) and metabolite analysis. Growth inhibition and suppression of phenylpropanoid metabolism can be genetically separated in ref4-3 by elimination of CDK8 kinase activity; however, the stunted growth of ref4-3 is not dependent on the phosphorylation event introduced by the G383S mutation. In addition, rather than perturbation of lignin biosynthesis, misregulation of DJC66, a gene encoding a DNAJ protein, is involved in the dwarfism of the med5 mutants. Together, our study reveals genetic interactions between Mediator tail and kinase module subunits and enhances our understanding of dwarfing in phenylpropanoid pathway mutants.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [2];  [3]; ORCiD logo [4]; ORCiD logo [1]
  1. Purdue Univ., West Lafayette, IN (United States). Dept. of Biochemistry; Purdue Univ., West Lafayette, IN (United States). Purdue Center for Plant Biology
  2. Purdue Univ., West Lafayette, IN (United States). Dept. of Biochemistry
  3. Purdue Univ., West Lafayette, IN (United States). Dept. of Biochemistry; Northwest Missouri State Univ., Maryville, MO (United States)
  4. Purdue Univ., West Lafayette, IN (United States). Dept. of Biochemistry; Purdue Univ., West Lafayette, IN (United States). Purdue University Center for Cancer Research
Publication Date:
Research Org.:
Purdue Univ., West Lafayette, IN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1597908
Alternate Identifier(s):
OSTI ID: 1501715
Grant/Contract Number:  
FG02-07ER15905; DE‐FG02‐07ER15905
Resource Type:
Accepted Manuscript
Journal Name:
New Phytologist
Additional Journal Information:
Journal Volume: 223; Journal Issue: 1; Journal ID: ISSN 0028-646X
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES

Citation Formats

Mao, Xiangying, Kim, Jeong Im, Wheeler, Mitchell T., Heintzelman, Anne K., Weake, Vikki M., and Chapple, Clint. Mutation of Mediator subunit $CDK$ counteracts the stunted growth and salicylic acid hyperaccumulation phenotypes of an Arabidopsis $MED$ mutant. United States: N. p., 2019. Web. doi:10.1111/nph.15741.
Mao, Xiangying, Kim, Jeong Im, Wheeler, Mitchell T., Heintzelman, Anne K., Weake, Vikki M., & Chapple, Clint. Mutation of Mediator subunit $CDK$ counteracts the stunted growth and salicylic acid hyperaccumulation phenotypes of an Arabidopsis $MED$ mutant. United States. doi:10.1111/nph.15741.
Mao, Xiangying, Kim, Jeong Im, Wheeler, Mitchell T., Heintzelman, Anne K., Weake, Vikki M., and Chapple, Clint. Mon . "Mutation of Mediator subunit $CDK$ counteracts the stunted growth and salicylic acid hyperaccumulation phenotypes of an Arabidopsis $MED$ mutant". United States. doi:10.1111/nph.15741. https://www.osti.gov/servlets/purl/1597908.
@article{osti_1597908,
title = {Mutation of Mediator subunit $CDK$ counteracts the stunted growth and salicylic acid hyperaccumulation phenotypes of an Arabidopsis $MED$ mutant},
author = {Mao, Xiangying and Kim, Jeong Im and Wheeler, Mitchell T. and Heintzelman, Anne K. and Weake, Vikki M. and Chapple, Clint},
abstractNote = {The Mediator complex functions as a hub for transcriptional regulation. MED5, an Arabidopsis Mediator tail subunit, is required for maintaining phenylpropanoid homeostasis. A semidominant mutation (ref4-3) that causes a single amino acid substitution in MED5b functions as a strong suppressor of the pathway, leading to decreased soluble phenylpropanoid accumulation, reduced lignin content and dwarfism. By contrast, loss of MED5 results in increased concentrations of phenylpropanoids. We used a reverse genetic approach to identify suppressors of ref4-3 and found that ref4-3 requires CDK8, a kinase module subunit of Mediator, to repress plant growth. The genetic interaction between MED5 and CDK8 was further characterized using mRNA-sequencing (RNA-seq) and metabolite analysis. Growth inhibition and suppression of phenylpropanoid metabolism can be genetically separated in ref4-3 by elimination of CDK8 kinase activity; however, the stunted growth of ref4-3 is not dependent on the phosphorylation event introduced by the G383S mutation. In addition, rather than perturbation of lignin biosynthesis, misregulation of DJC66, a gene encoding a DNAJ protein, is involved in the dwarfism of the med5 mutants. Together, our study reveals genetic interactions between Mediator tail and kinase module subunits and enhances our understanding of dwarfing in phenylpropanoid pathway mutants.},
doi = {10.1111/nph.15741},
journal = {New Phytologist},
number = 1,
volume = 223,
place = {United States},
year = {2019},
month = {3}
}

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