Distinct accumulation and remobilization of fructans in barley cultivars contrasting for photosynthetic performance and yield

Abstract

Fructans are easily mobile storage carbohydrate in crops. In barley (Hordeum vulgare L.), a variable amount of fructans is stored in the stem or remobilized to the grain after flowering, which might be impacted by the photosynthetic performance. The aim of this work was to analyze the connection between photosynthetic performance, fructan content and activity of genes involved in the synthesis (1-SST, sucrose:sucrose-1-fructosyltransferase and 6-SFT, sucrose:fructan-6-fructosyltransferase) and remobilization (1-FEH, fructan 1-exohydrolase) of fructans at three developmental growth stages: flowering, grain filling and ripening stage in two spring barley cultivars differing in their yield. Photosynthetic performance was assessed by using chlorophyll a fluorescence measurement expressed as total performance index (PItotal) and maximum quantum yield (Fv/Fm), fructan content was determined spectrophotometrically using resorcinol reagent and gene activity by semi-quantitative RT-PCR. The PItotal was higher in cultivar Jaran than in Astor, indicating its better photosynthetic performance. Cultivar Jaran accumulated significantly less fructans in three basal internodes compared to cultivar Astor. Such observations could be explained by concurrent synthesis and remobilization and better sink strength in cultivar Jaran due to congruent expression of genes regulating biosynthesis and fructan remobilization. On the other hand, the higher fructan content in basal internodes of cultivar Astor could possibly be the consequence of lower expression of 1-FEH gene responsible for fructan remobilization. Our results showed that fructan synthesis and remobilization to the grain are dependent on synchronized activity of regulatory genes, indicating a strong influence of photosynthetic performance and genotype.