title: Most photorespiratory genes are preferentially expressed in the bundle sheath cells of the C4 grass Sorghum bicolor.
abstract: One of the hallmarks of C4 plants is the division of labor between two different photosynthetic cell types, the mesophyll and the bundle sheath cells. C4 plants are of polyphyletic origin and, during the evolution of C4 photosynthesis, the expression of thousands of genes was altered and many genes acquired a cell type-specific or preferential expression pattern. Several lines of evidence, including computational modeling and physiological and phylogenetic analyses, indicate that alterations in the expression of a key photorespiration-related gene, encoding the glycine decarboxylase P subunit, was an early and important step during C4 evolution. Restricting the expression of this gene to the bundle sheath led to the establishment of a photorespiratory CO2 pump. We were interested in whether the expression of genes related to photorespiration remains bundle sheath specific in a fully optimized C4 species. Therefore we analyzed the expression of photorespiratory and C4 cycle genes using RNA in situ hybridization and transcriptome analysis of isolated mesophyll and bundle sheath cells in the C4 grass Sorghum bicolor It turns out that the C4 metabolism of Sorghum is based solely on the NADP-dependent malic enzyme pathway. The majority of photorespiratory gene expression, with some important exceptions, is restricted to the bundle sheath.
authors.affiliation: Institute of Plant Molecular and Developmental Biology, Universitätsstrasse 1, Heinrich-Heine-University, D-40225 Düsseldorf, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Döring
authors.affiliation: Institute of Plant Molecular and Developmental Biology, Universitätsstrasse 1, Heinrich-Heine-University, D-40225 Düsseldorf, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Streubel
authors.affiliation: Institute of Plant Biochemistry, Universitätsstrasse 1, Heinrich-Heine-University, D-40225 Düsseldorf, Germany Cluster of Excellence on Plant Sciences (CEPLAS) 'From Complex Traits towards Synthetic Modules', D-40225 Düsseldorf, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bräutigam
authors.affiliation: Institute of Plant Molecular and Developmental Biology, Universitätsstrasse 1, Heinrich-Heine-University, D-40225 Düsseldorf, Germany gowik@uni-duesseldorf.de.
authors.forename: Udo
authors.initials: U
authors.lastname: Gowik
mesh_terms: D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D017343:Genes, Plant / Q000502:physiology*; D017403:In Situ Hybridization; D010788:Photosynthesis / Q000235:genetics*; D018749:RNA, Plant / Q000235:genetics / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction; D045868:Sorghum / Q000166:cytology / Q000235:genetics* / Q000502:physiology
chemical_list: D018749:RNA, Plant
keywords: C4 photosynthesis; CO2 fixation; Sorghum bicolor.; differential gene expression; evolution; photorespiration