Publication Type: | Journal Article |
Year of Publication: | 2010 |
Authors: | Dal'Molin, CGomes de O, Quek, L-E, Palfreyman, RWilliam, Brumbley, SMichael, Nielsen, LKeld |
Journal: | Plant Physiology |
Volume: | 154 |
Issue: | 4 |
Date Published: | 2010 |
ISBN Number: | 00320889 |
Keywords: | Saccharum |
Abstract: | Leaves of C₄ grasses (such as maize [Zea mays], sugarcane [Saccharum officinarum], and sorghum [Sorghum bicolor]) form a classical Kranz leaf anatomy. Unlike C₃ plants, where photosynthetic CO₂ fixation proceeds in the mesophyll (M), the fixation process in C₄ plants is distributed between two cell types, the M cell and the bundle sheath (BS) cell. Here, we develop a C₄ genome-scale model (C4GEM) for the investigation of flux distribution in M and BS cells during C₄ photosynthesis. C4GEM, to our knowledge, is the first large-scale metabolic model that encapsulates metabolic interactions between two different cell types. C4GEM is based on the Arabidopsis (Arabidopsis thaliana) model (AraGEM) but has been extended by adding reactions and transporters responsible to represent three different C₄ subtypes (NADP-ME [for malic enzyme], NAD-ME, and phosphoenolpyruvate carboxykinase). C4GEM has been validated for its ability to synthesize 47 biomass components and consists of 1,588 unique reactions, 1,755 metabolites, 83 interorganelle transporters, and 29 external transporters (including transport through plasmodesmata). Reactions in the common C₄ model have been associated with well-annotated C₄ species (NADP-ME subtypes): 3,557 genes in sorghum, 11,623 genes in maize, and 3,881 genes in sugarcane. The number of essential reactions not assigned to genes is 131, 135, and 156 in sorghum, maize, and sugarcane, respectively. Flux balance analysis was used to assess the metabolic activity in M and BS cells during C₄ photosynthesis. Our simulations were consistent with chloroplast proteomic studies, and C4GEM predicted the classical C₄ photosynthesis pathway and its major effect in organelle function in M and BS. The model also highlights differences in metabolic activities around photosystem I and photosystem II for three different C₄ subtypes. Effects of CO₂ leakage were also explored. C4GEM is a viable framework for in silico analysis of cell cooperation between M and BS cells during photosynthesis and can be used to explore C₄ plant metabolism. |
URL: | http://www.jstor.org/stable/25758725 |
Short Title: | Plant Physiology |
C4GEM, a Genome-Scale Metabolic Model to Study C₄ Plant Metabolism
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