[Plants for Life Seminar] From fixation to end-product synthesis: following the path of carbon in C3 and C4 plants by dynamic 13CO2 labelling
Stephanie Arrivault, Max Planck Institute of Molecular Plant Physiology
| When |
23 Apr, 2019
from
02:30 pm to 03:30 pm |
|---|---|
| Where | Auditorium |
| Contact Name | Isabel Abreu |
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Title: From fixation to end-product synthesis: following the path of carbon in C3 and C4 plants by dynamic 13CO2 labelling
Speaker: Stephanie Arrivault
Affiliation: Max Planck Institute of Molecular Plant Physiology, Germany
Abstract
Understanding the regulation and integration of CO2 fixation with end-product synthesis and other pathways is one of the major challenges in plant biochemistry. Therefore, it is important to determine the temporal kinetics of carbon flow into central carbon metabolism. This can be achieved by supplying 13CO2 to plants, harvesting them by quenching at various time intervals and using MS-based methods to monitor the incorporation of 13C into metabolites of central carbon metabolism. Here we present the applications of such methods to Arabidopsis (C3) rosette leaves (Szecowka et al., 2013, Plant Cell), focusing on the possible reasons for an incomplete labelling of metabolites from the Calvin-Benson cycle after 1h of 13CO2 treatment, and to maize (C4) leaves (Arrivault et al., 2017 J Exp Bot.). C4 plants are historically classified into three biochemical subtypes based on the main enzyme involved in C4 acid decarboxylation: NADP-malic enzyme (NADP-ME), NAD-malic enzyme (NAD-ME) or phosphoenolpyruvate carboxykinase (PEPCK). However multiple lines of evidence suggest that more than one decarboxylation pathway might operate in parallel within the same leaf, implying that the classical assignment of C4 species into the three subtypes is an over-simplification. Our analyses confirmed that there is a concentration gradient of malate to drive diffusion from the mesophyll to the bundle sheath cells for decarboxylation by NADP-ME in maize but we also found concentration gradients of aspartate, alanine and phosphenolpyruvate that could drive metabolite transport associated with a NAD-ME and/or a PEPCK pathway, carrying 10-14% of the fixed carbon into the bundle sheath cells.
