title: The Recovery of Plastid Function Is Required for Optimal Response to Low Temperatures in Arabidopsis.
abstract: Cold acclimation is an essential response in higher plants to survive freezing temperatures. Here, we report that two independent mutant alleles of the H-subunit of Mg-chelatase, CHLH, gun5-1 and cch in Arabidopsis are sensitive to low temperatures. Plants were grown in photoperiodic conditions and exposed to low temperatures for short- and long-term periods. Tetrapyrrole biosynthesis was initially significantly inhibited in response to low temperature but recovered in wild type (Col-0), although the tetrapyrrole levels were lower in cold compared to control conditions. The gun5-1 and cch alleles showed an inability to recover chlorophyll biosynthesis in addition to a significant decrease in freezing tolerance. We found that the impaired plastid function in the CHLH mutant plants resulted in compromised de novo protein synthesis at low temperatures. The expression of the transcription factors CBF1-3 was super-induced in gun5-1 and cch mutant alleles but expression levels of their target genes, COR15a, COR47 and COR78 were similar or even lower compared to Col-0. In addition, the protein levels of COR15a were lower in gun5-1 and cch and a general defect in protein synthesis could be seen in the gun5-1 mutant following a 35S labelling experiment performed at low temperature. Taken together, our results demonstrate the importance of a functional chloroplast for the cold acclimation process and further suggest that impaired plastid function could result in inhibition of protein synthesis at low temperature.
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Kindgren
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden.
authors.forename: Carole
authors.initials: C
authors.lastname: Dubreuil
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden.
authors.forename: Åsa
authors.initials: Å
authors.lastname: Strand
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000483:Alleles; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000096:biosynthesis* / Q000235:genetics; D003080:Cold Temperature; D058639:Cold-Shock Response / Q000502:physiology*; D009154:Mutation; D018087:Plastids / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins