Arabidopsis MDA1, a nuclear-encoded protein, functions in chloroplast development and abiotic stress responses.
Most chloroplast and mitochondrial proteins are encoded by nuclear genes, whose functions remain largely unknown because mutant alleles are lacking. A reverse genetics screen for mutations affecting the mitochondrial transcription termination factor (mTERF) family in Arabidopsis thaliana allowed us to identify 75 lines carrying T-DNA insertions. Two of them were homozygous for insertions in the At4g14605 gene, which we dubbed MDA1 (MTERF DEFECTIVE IN Arabidopsis1). The mda1 mutants exhibited altered chloroplast morphology and plant growth, and reduced pigmentation of cotyledons, leaves, stems and sepals. The mda1 mutations enhanced salt and osmotic stress tolerance and altered sugar responses during seedling establishment, possibly as a result of reduced ABA sensitivity. Loss of MDA1 function caused up-regulation of the RpoTp/SCA3 nuclear gene encoding a plastid RNA polymerase and modified the steady-state levels of chloroplast gene transcripts. Double mutant analyses indicated that MDA1 and the previously described mTERF genes SOLDAT10 and RUG2 act in different pathways. Our findings reveal a new role for mTERF proteins in the response to abiotic stress, probably through perturbed ABA retrograde signalling resulting from a disruption in chloroplast homeostasis.
Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, Elche, Spain.
Pedro
P
Robles
José Luis
JL
Micol
Víctor
V
Quesada
D000483:Alleles; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D060365:Chloroplast Proteins / Q000235:genetics / Q000502:physiology*; D002736:Chloroplasts / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D017343:Genes, Plant / Q000235:genetics; D018745:Genome, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006706:Homeostasis; D006720:Homozygote; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000235:genetics; D009995:Osmosis; D010858:Pigmentation; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014157:Transcription Factors
D029681:Arabidopsis Proteins; C578065:At4g14605 protein, Arabidopsis; D060365:Chloroplast Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D012321:DNA-Directed RNA Polymerases