ABSTRACT
Photosynthesis in higher land plants is a complex process involving several proteins encoded by both nuclear and chloroplast genomes that require a highly coordinated gene expression. Significant changes in plastid differentiation and biochemical processes are associated with the deletion of chloroplast genes. In this study we report the genome-wide responses caused by the deletion of tobacco psaA and psbA genes coding core components of photosystem I (PSI) and photosystem II (PSII), respectively, generated through a chloroplast genetic engineering approach. Transcriptomic and quantitative proteomic analysis showed the down regulation of specific groups of nuclear and chloroplast genes involved in photosynthesis, energy metabolism and chloroplast biogenesis. Moreover, our data show simultaneous activation of several defense and stress responsive genes including those involved in reactive oxygen species (ROS) scavenging mechanisms. A major finding is the differential transcription of the plastome of deletion mutants: genes known to be transcribed by the plastid encoded polymerase (PEP) were generally down regulated while those transcribed by the nuclear encoded polymerase (NEP) were up regulated, indicating simultaneous activation of multiple signaling pathways in response to disruption of PSI and PSII complexes. The genome wide transcriptomic and proteomic analysis of the ∆psaA and ∆psbA deletion mutants revealed a simultaneous up and down regulation of the specific groups of genes located in nucleus and chloroplasts suggesting a complex circuitry involving both retrograde and anterograde signaling mechanisms responsible for the coordinated expression of nuclear and chloroplast genomes.
Subject(s)
Gene Deletion , Gene Expression Profiling , Genome, Plant , Nicotiana/genetics , Plant Proteins/genetics , Proteome , Base Sequence , Chromatography, Liquid , DNA Primers , Reverse Transcriptase Polymerase Chain Reaction , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Nicotiana/metabolism , Nicotiana/physiologyABSTRACT
Genomic components of a begomovirus isolated from tomato plants showing leaf curl and stunting symptoms in farmer's fields at Hessarghatta village near Bangalore, India, were cloned by rolling-circle amplification. The virus was identified as a variant of strain C of the species Tomato leaf curl Bangalore virus and designated as Tomato leaf curl Bangalore virus-C[India:Hessarghatta:2008], ToLCBV-C[IN:Hess:08]. The betasatellite isolated from these samples belongs to the betasatellite species Tomato leaf curl Bangalore betasatellite. ToLCBV-C[IN:Hess:08] induced severe symptoms in Nicotiana benthamiana and Solanum lycopersicum plants when co-inoculated with the cognate betasatellite, Tomato leaf curl Bangalore betasatellite-[India:Hessarghatta:2008], ToLCBB-[IN:Hess:08] and with two other non-cognate betasatellites, Cotton leaf curl Multan betasatellite-[India:SriGanganagar:2002] and Luffa leaf distortion betasatellite-[India:Luffa:2004].
