A search for factors influencing etioplast-chloroplast transition.
Chloroplast biogenesis in angiosperm plants requires the light-dependent transition from an etioplast stage. A key factor in this process is NADPH:protochlorophyllide oxidoreductase A (PORA), which catalyzes the light-dependent reduction of protochlorophyllide to chlorophyllide. In a recent study the chloroplast outer envelope channel OEP16 was described to be involved in etioplast to chloroplast transition by forming the translocation pore for the precursor protein of PORA [Pollmann et al. (2007) Proc Natl Acad Sci USA 104:2019-2023]. This hypothesis was based on the finding that a single OEP16.1 knockout mutant in Arabidopsis thaliana was severely affected during seedling de-etiolation and PORA protein was absent in etioplasts. In contrast, in our study the identical T-DNA insertion line greened normally and showed normal etioplast to chloroplast transition, and mature PORA was present in etioplasts [Philippar et al. (2007) Proc Natl Acad Sci USA 104:678-683]. To address these conflicting results regarding the function of OEP16.1 for PORA import, we analyzed several lines segregating from the original OEP16.1 T-DNA insertion line. Thereby we can unequivocally show that the loss of OEP16.1 neither correlates with impaired PORA import nor causes the observed de-etiolation phenotype. Furthermore, we found that the mutant line contains at least 2 additional T-DNA insertions in the genes for the extracellular polygalacturonase converter AroGP1 and the plastid-localized chorismate mutase CM1. However, detailed examination of the de-etiolation phenotype and a genomewide transcriptional analysis revealed no direct influence of these genes on etioplast to chloroplast transition in Arabidopsis cotyledons.
Pudelski
Birgit
B
Biochemie und Physiologie der Pflanzen, Department Biologie I-Botanik, Ludwig-Maximilians-Universität München, Grosshadernerstrasse 2-4, D-82152 Planegg-Martinsried, Germany.
Soll
Jürgen
J
Philippar
Katrin
K
D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D018548:Cotyledon / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D007473:Ion Channels / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000378:metabolism; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D007473:Ion Channels; C512221:OEP16-L protein, Arabidopsis; D012333:RNA, Messenger; C036483:T-DNA; D044925:Oxidoreductases Acting on CH-CH Group Donors; C023886:protochlorophyllide reductase