Interaction of trehalose and ascorbic acid in growing Arabidopsis seedlings

Trehalose is an important disaccharide signal metabolite in plants which is involved in various aspects of plant function such as response to stress, photosynthesis and carbon allocation and partitioning. A mutant of Arabidopsis lacking trehalose-6-phosphate synthase activity (tps1) accumulates ascorbate. Exogenous ascorbate Application ameliorates trehalose induced growth inhibition of wild type Arabidopsis seedlings and affects its carbon partitioning. Thus, unknown interactions between trehalose and ascorbate metabolisms are expected. This research has tried to reveal part of these interactive effects by analyzing some growth and biochemical parameters of Arabidopsis seedlings fed with sorbitol (100 mM) as control, trehalose (100 mM), trehalose plus ascorbate (0.1 mM), and ascorbate alone. Trehalose fed plants displayed reduced root and shoot growth and higher levels of hydrogen peroxide, anthocyanins and greater catalase, peroxidase and polyphenol oxidase activities along with reduced chlorophyll contents. Exogenous ascorbate application reversed these effects which suggest the prevailing oxidative stress in trehalose fed plants has probably compromised their growth. Control plants accumulated starch in root tips whereas, trehalose fed plants accumulated starch in cotyledons. The effect of trehalose on carbon allocation, however, was reversed following ascorbate application. It was assumed that trehalose feeding affects plant source-sink relations, thus by imposing oxidative stress on roots it reduces sink strength accompanied with declined withdrawal of carbohydrate from shoot. As a result of oil body mobilization in cotyledons, starch is accumulated in this organ. The exogenous ascorbate, however, by promoting root growth increases sink strength, thus carbon is withdrawn more from cotyledons. This leads to starch build up in roots. Unexpectedly, the greatest level of endogenous ascorbate was found in trehalose fed plants which might imply ascorbate utilization for confronting oxidative stress is somehow restricted.