The barley plastome mutant CL2 affects expression of nuclear and chloroplast housekeeping genes in a cell-age dependent manner

Abstract

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.

The transcription machineries of plant mitochondria and chloroplasts: Composition, function, and regulation

“…3; Rodermel, 2001;Gray, 2003;Gray et al, 2003;Brown et al, 2005;Kleine et al, 2009;Galvez-Valdivieso and Mullineaux, 2010;Inaba, 2010;Pfannschmidt, 2010). The nuclear RpoTp gene in barley, encoding the NEP activity, is one of the targets of plastid signal(s) (Emanuel et al, 2004;Colombo et al, 2008). Retrograde signaling coordinates therefore the expression of PEP and NEP as a prerequisite of concerted gene expression in both plastids and the nucleus (Fig.…”

Spontaneous Chloroplast Mutants Mostly Occur by Replication Slippage and Show a Biased Pattern in the Plastome of Oenothera

“…Importantly, phenotypes of plastome mutants go beyond simple bleaching. Some plastome mutants display mild chlorotic effects, are developmentally impaired or sensitive to environmental factors, and show mottled phenotypes and/or bleach reversibly (Kirk and Tilney-Bassett, 1978;Stubbe and Herrmann, 1982;Chia et al, 1986;Archer and Bonnett, 1987;Colombo et al, 2008;Hirao et al, 2009;Landau et al, 2009;Greiner, 2012;Figures 1B to 1D, Table 1). A number of mutant lines have been described that display unexpected phenotypes, such as mutant plastids having a phenotypic effect on wild-type plastids in the same cell (Michaelis, 1957) or mutations that confer drought and temperature tolerance (Usatov et al, 2004;Mashkina et al, 2010).…”

Proteome analysis of Fusarium head blight in grains of naked barley (Hordeum vulgare subsp. nudum)

“…Plastid RNA polymerase uses four ribonucleoside triphosphates as substrates to catalyze the transcription of DNA into RNA 40, 41. The functions of the up‐regulated plastid RNA polymerase are involved in the translation of house‐keeping genes and photosynthesis genes 42. The up‐regulation here can possibly be explained by the loss of function in barley chloroplasts of Fusarium ‐infected tissue, because chloroplasts are known to be the organelles most affected by Fusarium infection 22.…”