title: Leaf Variegation of Thylakoid Formation1 Is Suppressed by Mutations of Specific σ-Factors in Arabidopsis.
abstract: Thylakoid Formation1 (THF1) has been shown to play roles in chloroplast development, resistance to excessive light, and chlorophyll degradation in Arabidopsis (Arabidopsis thaliana). To elucidate mechanisms underlying THF1-regulated chloroplast development, we mutagenized thf1 seeds with ethyl methanesulfonate and screened second-site recessive mutations that suppress its leaf variegation phenotype. Here, we characterized a unique suppressor line, 42-6, which displays a leaf virescent phenotype. Map-based cloning and genetic complementation results showed that thf1 variegation was suppressed by a mutation in σ-FACTOR6 (SIG6), which is a plastid transcription factor specifically controlling gene expression through the plastid-encoded RNA polymerase. Northern-blot analysis revealed that plastid gene expression was down-regulated in not only 42-6 and sig6 but also, thf1 at the early stage of chloroplast development. Interestingly, mutations in SIG2 but not in other σ-factors also suppressed thf1 leaf variegation. Furthermore, we found that leaf variegation of thf1 and var2 could be suppressed by several virescent mutations, including yellow seedling1, brz-insensitive-pale green2, and nitric oxide-associated protein1, indicating that virescent mutations suppress leaf variegation. Taken together, our results provide unique insights into thf1-mediated leaf variegation, which might be triggered by defects in plastid gene transcription.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Fenhong
authors.identifier: http://orcid.org/0000-0002-1361-6336
authors.initials: F
authors.lastname: Hu
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Wu
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Ye
authors.identifier: http://orcid.org/0000-0001-6509-5723
authors.initials: Y
authors.lastname: Xie
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China huangjr@sibs.ac.cn.
authors.forename: Jirong
authors.identifier: http://orcid.org/0000-0002-3553-0031
authors.initials: J
authors.lastname: Huang
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000528:radiation effects / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015152:Blotting, Northern; D002736:Chloroplasts / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D017343:Genes, Plant; D016153:Genes, Suppressor; D008027:Light; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism; D013489:Suppression, Genetic / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; C000590916:SIG2 protein, Arabidopsis; C502611:SIG6 protein, Arabidopsis; D012808:Sigma Factor; C512069:THF1 protein, Arabidopsis