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A role for Carbon metabolism in leaf growth response to soil water deficit ? An integrated perspective
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Edité par CCSD -
International audience. Understanding what limits plant growth under water deficit is an important issue because it could help in identifying key processes at which genetic variation of stress tolerance relies on, and provide prospects for breeding. We evaluated responses to soil water deficit in C metabolism and leaf growth in Arabidopsis using two complementary approaches. First, we questioned whether water deficit depreciates or improves the C status of the plant. Most activities of enzymes from central metabolism were increased under water deficit, while all C metabolites accumulated. Strikingly, only glutamate dehydrogenase and acid invertase activities, which are known to increase under sugar starvation, decreased under water deficit. A survey of 20 sugar responsive genes then confirmed that in WT, carbon status was improved by water deficit. Furthermore, it showed that C status was improved at night in the starchless mutant pgm, which experiences C starvation every night under well watered conditions. Second, we evaluated the impact of C metabolism on the response of leaf growth to water deficit by using a set of mutants affected in starch metabolism. During the early steps following the emergence of a leaf, strong day-night growth fluctuations were visible in these mutants only, in phase with the fluctuations of their C status. Moreover, leaf growth at night in these mutants was increased by water deficit as compared to well watered conditions. Finally, the extent of the daily accumulation of transient C forms was strongly related to the rate of leaf growth at night, and this association became looser as the level of water deficit increased. Taken together, these findings suggest that C metabolism has a strong impact on growth in the early, heterotrophic, stages of the leaf, but that this influence decreases with leaf age and water deficit, probably as other limitations take place.
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