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C4 photosynthesis is a carbon-concentrating mechanism that increases delivery of carbon dioxide to RuBisCO and as a consequence reduces photorespiration. The C4 pathway is therefore beneficial in environments that promote high photorespiration. This pathway has evolved many times, and involves restricting gene expression to either mesophyll or bundle sheath cells. Here we review the regulatory mechanisms that control cell-preferential expression of genes in the C4 cycle. From this analysis, it is clear that the C4 pathway has a complex regulatory framework, with control operating at epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels. Some genes of the C4 pathway are regulated at multiple levels, and we propose that this ensures robust expression in each cell type. Accumulating evidence suggests that multiple genes of the C4 pathway may share the same regulatory mechanism. The control systems for C4 photosynthesis gene expression appear to operate in C3 plants, and so it appears that pre-existing mechanisms form the basis of C4 photosynthesis gene expression. [ABSTRACT FROM AUTHOR]

Identification of potential cis-regulatory motifs controlling the development of C4 photosynthesis is a major focus of current research. In this study, we used time-series RNA-seq data collected from etiolated maize and rice leaf tissues sampled during a de-etiolation process to systematically characterize the expression patterns of C4-related genes and to further identify potential cis elements in five different genomic regions (i.e. promoter, 5'UTR, 3'UTR, intron, and coding sequence) of C4 orthologous genes. The results demonstrate that although most of the C4 genes show similar expression patterns, a number of them, including chloroplast dicarboxylate transporter 1, aspartate aminotransferase, and triose phosphate transporter, show shifted expression patterns compared with their C3 counterparts. A number of conserved short DNA motifs between maize C4 genes and their rice orthologous genes were identified not only in the promoter, 5'UTR, 3'UTR, and coding sequences, but also in the introns of core C4 genes. We also identified cis-regulatory motifs that exist in maize C4 genes and also in genes showing similar expression patterns as maize C4 genes but that do not exist in rice C3 orthologs, suggesting a possible recruitment of pre-existing cis-elements from genes unrelated to C4 photosynthesis into C4 photosynthesis genes during C4 evolution. [ABSTRACT FROM AUTHOR]

In the leaves of most C4 plants, mesophyll (M) and bundle sheath (BS) cells develop and maintain highly differentiated biochemical networks. Separation and analysis of M and BS cells has greatly influenced our understanding of the C4 pathway. A number of approaches including mechanical separation, digestion with cell wall-degrading cocktails, laser-capture microdissection, and leaf rolling have been used to isolate these cell types. Although leaf rolling is conceptually and practically the simplest method, to date it has only been used to assess the metabolite content of M cells from C4 leaves of maize. This study reports an adapted leaf-rolling method for the isolation of high-quality RNA from M cells of sorghum. Analysis of leaf cell structure, RNA integrity, and transcript abundance of marker genes demonstrated that the sap collected by leaf rolling was from M cells and had no significant contamination. It was concluded that leaf rolling is a fast, cheap, and efficient method of measuring transcript abundance in M cells of sorghum. [ABSTRACT FROM AUTHOR]

In which cells of the flower volatile biosynthesis takes place is unclear. In rose and snapdragon, some enzymes of the volatile phenylpropanoid/benzenoid pathway have been shown to be present in the epidermal cells of petals. It is therefore generally believed that the production of these compounds occurs in these cells. However, whether the entire pathway is active in these cells and whether it is exclusively active in these cells remains to be proven. Cell-specific transcription factors activating these genes will determine in which cells they are expressed. In petunia, the transcription factor EMISSION OF BENZENOIDS II (EOBII) activates the ODORANT1 (ODO1) promoter and the promoter of the biosynthetic gene isoeugenol synthase (IGS). The regulator ODO1 in turn activates the promoter of the shikimate gene 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). Here the identification of a new target gene of ODO1, encoding an ABC transporter localized on the plasma membrane, PhABCG1, which is co-expressed with ODO1, is described. PhABCG1 expression is up-regulated in petals overexpressing ODO1 through activation of the PhABCG1 promoter. Interestingly, the ODO1, PhABCG1, and IGS promoters were active in petunia protoplasts originating from both epidermal and mesophyll cell layers of the petal, suggesting that the volatile phenylpropanoid/benzenoid pathway in petunia is active in these different cell types. Since volatile release occurs from epidermal cells, trafficking of (volatile) compounds between cell layers must be involved, but the exact function of PhABCG1 remains to be resolved. [ABSTRACT FROM PUBLISHER]

C 4 photosynthesis is a carbon-concentrating mechanism that increases delivery of carbon dioxide to RuBisCO and as a consequence reduces photorespiration. The C 4 pathway is therefore beneficial in environments that promote high photorespiration. This pathway has evolved many times, and involves restricting gene expression to either mesophyll or bundle sheath cells. Here we review the regulatory mechanisms that control cell-preferential expression of genes in the C 4 cycle. From this analysis, it is clear that the C 4 pathway has a complex regulatory framework, with control operating at epigenetic, transcriptional, post-transcriptional, translational, and post-translational levels. Some genes of the C 4 pathway are regulated at multiple levels, and we propose that this ensures robust expression in each cell type. Accumulating evidence suggests that multiple genes of the C 4 pathway may share the same regulatory mechanism. The control systems for C 4 photosynthesis gene expression appear to operate in C 3 plants, and so it appears that pre-existing mechanisms form the basis of C 4 photosynthesis gene expression., (© The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Identification of potential cis-regulatory motifs controlling the development of C4 photosynthesis is a major focus of current research. In this study, we used time-series RNA-seq data collected from etiolated maize and rice leaf tissues sampled during a de-etiolation process to systematically characterize the expression patterns of C4-related genes and to further identify potential cis elements in five different genomic regions (i.e. promoter, 5'UTR, 3'UTR, intron, and coding sequence) of C4 orthologous genes. The results demonstrate that although most of the C4 genes show similar expression patterns, a number of them, including chloroplast dicarboxylate transporter 1, aspartate aminotransferase, and triose phosphate transporter, show shifted expression patterns compared with their C3 counterparts. A number of conserved short DNA motifs between maize C4 genes and their rice orthologous genes were identified not only in the promoter, 5'UTR, 3'UTR, and coding sequences, but also in the introns of core C4 genes. We also identified cis-regulatory motifs that exist in maize C4 genes and also in genes showing similar expression patterns as maize C4 genes but that do not exist in rice C3 orthologs, suggesting a possible recruitment of pre-existing cis-elements from genes unrelated to C4 photosynthesis into C4 photosynthesis genes during C4 evolution., (© The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.)