Mutants for photosystem I subunit D of Arabidopsis thaliana: effects on photosynthesis, photosystem I stability and expression of nuclear genes for chloroplast functions.
In Arabidopsis thaliana, the D-subunit of photosystem I (PSI-D) is encoded by two functional genes, PsaD1 and PsaD2, which are highly homologous. Knock-out alleles for each of the loci have been identified by a combination of forward and reverse genetics. The double mutant psad1-1 psad2-1 is seedling-lethal, high-chlorophyll-fluorescent and deficient for all tested PSI subunits, indicating that PSI-D is essential for photosynthesis. In addition, psad1-1 psad2-1 plants show a defect in the accumulation of thylakoid multiprotein complexes other than PSI. Of the single-gene mutations, psad2 plants behave like wild-type (WT) plants, whereas psad1-1 markedly affects the accumulation of PsaD mRNA and protein, and photosynthetic electron flow. Additional effects of the psad1-1 mutation include a decrease in growth rate under greenhouse conditions and downregulation of the mRNA expression of most genes involved in the light phase of photosynthesis. In the same mutant, a marked decrease in the levels of PSI and PSII polypeptides is evident, as well as a light-green leaf coloration and increased photosensitivity. Increased dosage of PsaD2 in the psad1-1 background restores the WT phenotype, indicating that PSI-D1 and PSI-D2 have redundant functions.
Abteilung für Pflanzenzüchtung und Ertragsphysiologie, Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné Weg 10, D-50829 Köln, Germany.
Anna
A
Ihnatowicz
Paolo
P
Pesaresi
Claudio
C
Varotto
Erik
E
Richly
Anja
A
Schneider
Peter
P
Jahns
Francesco
F
Salamini
Dario
D
Leister
D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics*; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics; D004579:Electron Transport; D018628:Gene Dosage; D015870:Gene Expression; D017343:Genes, Plant; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010788:Photosynthesis / Q000235:genetics; D045331:Photosystem I Protein Complex / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; D018744:DNA, Plant; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant