Carbon allocation and sugar status in individual cells of barley leaves affects expression of sucrose:fructan 6-fructosyltransferase gene

Heterogeneity of function in plant tissues requires precise regulation of metabolic systems controlling resource allocation at the level of single cells. Differential distribution of metabolites between epidermis, mesophyll and parenchymatous bundle sheath (PBS) cells has already been demonstrated in barley (Hordeum vulgare L.) source leaves and partitioning of sugars in barley leaves has been proven to be highly cell-type specific. Carbohydrate metabolism of barley leaves induced to accumulate sucrose and fructans was investigated further at the individual cell level, using single cell sampling and analysis techniques. A novel approach using reverse transcription followed by polymerase chain reaction (RT-PCR) was used to analyse expression of the enzyme Sucrose: Fructan 6-Fructosyltransferase (6-SFT) in individual cells of barley leaves. Accumulation of sucrose and the synthesis of fructans were induced by reducing export of sugars from leaves (root cooling), by increasing photosynthesis (high photon fluence rates), or by supplying sugars exogenously. In all cases there was a positive qualitative correlation between the presence of 6-SFT transcripts and accumulation of fructan and sucrose in both mesophyll and PBS cells.