Unraveling mannitol metabolism in celery plants

MINEN, ROMINA I.; IGLESIAS, ALBERTO A.; FIGUEROA, CARLOS M.

Buenos Aires

Congreso; Reunión conjunta de sociedades de biociencias; 2017

SAIB y otras

Sugar alcohols (like mannitol and glucitol) are major photosyntheticproducts in a significant number of agronomically important species.These metabolites also play a key role as compatible solutesunder different abiotic stress conditions (including salinity, droughtand cold). In celery (Apium graveolens) almost 80% of newly fixedCO2 is equally partitioned between sucrose and mannitol, while onlya small part is allocated to starch. Carbon partitioning in these plantsis more complex than in other species and must be orchestrated accordingly.However, the molecular mechanisms regulating mannitolsynthesis, storage and transport are far from being well understood.In this work, we grew celery plants under long (16 h), normal (12h) and short (8 h) photoperiods. Leaves were harvested every 2h for a complete light/dark cycle to measure the levels of solublesugars and starch. Additionally, we produced and characterizedmannose 6-phosphate reductase and mannitol dehydrogenase, thekey enzymes for mannitol synthesis and degradation, respectively.These proteins were also used to quantify mannose 6-phosphateand mannitol in samples from celery plants grown under differentconditions. We found that accumulation of both starch and solublesugars is higher in longer photoperiods. Interestingly, the pattern ofstarch accumulation differs from that observed for Arabidopsis thaliana,which accumulates large amounts of starch in leaves duringthe photoperiod to use it as carbon source during the following night.Our results suggest that carbon allocation is differentially regulatedin celery leaves and reveal that caution should be taken when extrapolatingresults from model plants to other species.