The control of source to sink carbon flux during tuber development in potato

We have used top-down metabolic control analysis to investigate the control of carbon flux through potato (Solanum tuberosum) plants during tuberisation. The metabolism of the potato plant was divided into two blocks of reactions (the source and sink blocks) that communicate through the leaf apoplastic sucrose pool. Flux was measured as the transfer of 14C from CO2 to the tuber. Flux and apoplastic sucrose concentration were varied either by changing the light intensity or using transgenic manipulations that specifically affect the source or sink blocks, and elasticity coefficients were measured. We have provided evidence in support of our assumption that apoplastic sucrose is the only communicating metabolite between the source and sink blocks. The elasticity coefficients were used to calculate the flux control coefficients of the source and sink blocks, which were 0.8 and 0.2, respectively. This work suggests that the best strategy for the manipulation of tuber yield in potato will involve increases in photosynthetic capacity, rather than sink metabolism

Leaf carbohydrate controls over Arabidopsis growth and response to elevated CO2: an experimentally based model

Transient starch production is thought to strongly control plant growth and response to elevated CO2. We tested this hypothesis with an experimentally based mechanistic model in Arabidopsis thaliana. Experiments were conducted on wild-type (WT) A. thaliana, starch-excess (sex1) and starchless (pgm) mutants under ambient and elevated CO2 conditions to determine parameters and validate the model. The model correctly predicted that mutant growth is approx. 20% of that in WT, and the absolute response of both mutants to elevated CO2 is an order of magnitude lower than in WT. For sex1, direct starch unavailability explained the growth responses. For pgm, we demonstrated experimentally that maintenance respiration is proportional to leaf soluble sugar concentration, which gave the necessary feedback mechanism on modelled growth. Our study suggests that the effects of sugar-starch cycling on growth can be explained by simple allocation processes, and the maximum rate of leaf growth (sink capacity) exerts a strong control over the response to elevated CO2 of herbaceous plants such as A. thaliana

Starch content and yield increase as a result of altering adenylate pools in transgenic plants

Starch represents the most important carbohydrate used for food and feed purposes. With the aim of increasing starch content, we decided to modulate the adenylate pool by changing the activity of the plastidial adenylate kinase in transgenic potato plants. As a result, we observed a substantial increase in the level of adenylates and, most importantly, an increase in the level of starch to 60% above that found in wild-type plants. In addition, concentrations of several amino acids were increased by a factor of 2–4. These results are particularly striking because this genetic manipulation also results in an increased tuber yield. The modulation of the plastidial adenylate kinase activity in transgenic plants therefore represents a potentially very useful strategy for increasing formation of major storage compounds in heterotrophic tissues of higher plants

13C-isotope-based protocol for prenyl lipid metabolic analysis in zebrafish embryos

Metabolism has a decisive role in many fundamental biological processes, including organism development and tissue homeostasis. Here we describe a protocol for fast and reliable 13C-isotope-based in vivo metabolic profiling. This protocol covers the loading of isotope precursor; extraction, preparation and quantification of the labeled lipid metabolites (e.g., the prenyl lipid CoQ10) by the means of HPLC-MS; and its analysis in zebrafish embryos. This protocol can be applied to different types of experimental settings, including tissue-specific metabolic analyses or dynamic metabolic changes that occur during vertebrate embryogenesis. The protocol takes 5\u20137 d to complete, requiring minimal equipment and analytical expertise, and it represents a unique alternative to the existing ex vivo (e.g., cell lines) isotope-based metabolic methods. This procedure represents a valuable approach for researchers interested in studying the effect of gene manipulation on lipid metabolism in zebrafish and in understanding the genetic conditions that result in metabolism dysfunction