The barley plastome mutant CL2 affects expression of nuclear and chloroplast housekeeping genes in a cell-age dependent manner.
The barley plastome mutant CL2 (cytoplasmic line 2) carries a point mutation in the infA gene, a homologue of the bacterial gene for the conserved translation initiator factor 1 (IF1). The function of infA in plastids is not known. The mutation in CL2 leads to a temporal chlorophyll deficiency in the primary leaf blade that is normalised in the basal and middle parts during further development. We have compared the expression of selected nuclear and plastid genes in different parts of primary leaves of CL2 and wild-type and found no indication for an adverse effect of the mutation on plastidial transcription. We observed an enhanced expression of RpoTp (encoding the phage-type nuclear-encoded plastid RNA polymerase) suggested to be caused by retrograde plastid signalling. Decreased amounts of plastid rRNA in basal and top sections are in agreement with the idea that the mutation in infA leads to a time- and position-dependent defect of plastid translation that causes a delay in plastid development. The normalisation of the phenotype in the middle section of CL2 leaves correlates with wild-type levels of chloroplast 16S rRNA and RbcL and increased expression of plastid housekeeping genes. The normalisation was not observed in cells at the tip of CL2 leaves suggesting different ways of regulating chloroplast development in cells at the tip of primary barley leaves as compared with other leaf sections.
Colombo
Noemí
N
Instituto de Genética Ewald A. Favret, CICVyA, CNIA, INTA, CC 25, B1712WAA Castelar, Buenos Aires, Argentina. ncolombo@cnia.inta.gov.ar
Emanuel
Carola
C
Lainez
Verónica
V
Maldonado
Sara
S
Prina
Alberto R
AR
Börner
Thomas
T
D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D016922:Cellular Senescence / Q000235:genetics; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D017931:DNA Primers / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D039642:Eukaryotic Initiation Factors / Q000235:genetics / Q000378:metabolism; D017343:Genes, Plant; D054628:Genome, Chloroplast; D001467:Hordeum / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D014158:Transcription, Genetic
D017931:DNA Primers; D039642:Eukaryotic Initiation Factors; D010940:Plant Proteins; D012321:DNA-Directed RNA Polymerases; C486921:RpoTp protein, Hordeum vulgare