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Malate as a key carbon source of leaf dark-respired CO2 across different environmental conditions in potato plants.

ABSTRACT: Dissimilation of carbon sources during plant respiration in support of metabolic processes results in the continuous release of CO2. The carbon isotopic composition of leaf dark-respired CO2 (i.e. ? (13) C R ) shows daily enrichments up to 14.8‰ under different environmental conditions. However, the reasons for this (13)C enrichment in leaf dark-respired CO2 are not fully understood, since daily changes in ?(13)C of putative leaf respiratory carbon sources (? (13) C RS ) are not yet clear. Thus, we exposed potato plants (Solanum tuberosum) to different temperature and soil moisture treatments. We determined ? (13) C R with an in-tube incubation technique and ? (13) C RS with compound-specific isotope analysis during a daily cycle. The highest ? (13) C RS values were found in the organic acid malate under different environmental conditions, showing less negative values compared to ? (13) C R (up to 5.2‰) and compared to ? (13) C RS of soluble carbohydrates, citrate and starch (up to 8.8‰). Moreover, linear relationships between ? (13) C R and ? (13) C RS among different putative carbon sources were strongest for malate during daytime (r(2)=0.69, P?0.001) and nighttime (r(2)=0.36, P?0.001) under all environmental conditions. A multiple linear regression analysis revealed ? (13) C RS of malate as the most important carbon source influencing ? (13) C R . Thus, our results strongly indicate malate as a key carbon source of (13)C enriched dark-respired CO2 in potato plants, probably driven by an anapleurotic flux replenishing intermediates of the Krebs cycle.

SUBMITTER: Lehmann MM

PROVIDER: S-EPMC4566975 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature

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Malate as a key carbon source of leaf dark-respired CO2 across different environmental conditions in potato plants.

Lehmann Marco M MM Rinne Katja T KT Blessing Carola C Siegwolf Rolf T W RT Buchmann Nina N Werner Roland A RA

Journal of experimental botany 20150702 19

Dissimilation of carbon sources during plant respiration in support of metabolic processes results in the continuous release of CO2. The carbon isotopic composition of leaf dark-respired CO2 (i.e. δ (13) C R ) shows daily enrichments up to 14.8‰ under different environmental conditions. However, the reasons for this (13)C enrichment in leaf dark-respired CO2 are not fully understood, since daily changes in δ(13)C of putative leaf respiratory carbon sources (δ (13) C RS ) are not yet clear. Thus, ...[more]

PMID: 26139821

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Project description:Responses to altered source–sink balance have been characterized in many crops at the physiological level, but the underlying genetic and molecular mechanisms are largely unknown. Detailed transcriptional profiling was performed in partially defoliated and shaded tomato plants to explore the effect of reduced source-to-sink ratio on molecular changes in the remaining source leaves. Transcription profiles of the remaining leaves 48 h after partial defoliation or partial shading were compared to leaves of control plants. Common significantly altered genes in the two treatments were assumed to be related to the reduced source-to-sink ratio. Sets of major genes in the abscisic acid, ethylene and gibberellin signal-transduction pathways were downregulated by both treatments. On the other hand, genes encoding cytokinin biosynthesis were upregulated. Most genes coding for transcription factors were also downregulated, especially those related to biotic and abiotic stress responses. Perhaps the most pronounced effect of reduced source-to-sink ratio was related to genes involved in the regulation of photosynthetic activity. Numerous genes coding for light-harvesting proteins, as well as those encoding plastocyanin, ferredoxin and ferredoxin NADP+ oxidoreductase were upregulated. Direct spectrophotometric analyses showed higher maximal potential activity of photosystem I with reduced source-to-sink ratio. As expected, the increased capacity for photosynthetic activity was associated with upregulation of almost all genes coding for the Calvin–Benson cycle and those encoding ATP biosynthesis in the mitochondria. Numerous transcriptional changes were observed 48 h after reducing source-to-sink ratio. Major genes in the photosynthetic-activity pathways were upregulated, whereas those in the pathways of defense mechanisms and responses to stress were downregulated. Genes involved in leaf senescence were also downregulated, suggesting that in addition to increased photosynthetic activity, the remaining leaves undergo a process of rejuvenation.

Dataset Information

Malate as a key carbon source of leaf dark-respired CO2 across different environmental conditions in potato plants.

Publications

Malate as a key carbon source of leaf dark-respired CO2 across different environmental conditions in potato plants.

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