Fig. 8.

Schematic diagram of grain development of the pAsGlo1:HvCslF6 transgenic line (A–C) relative to the wild type. (A) In transgenic endosperm, the early up-regulation of HvCslF6 gene expression relative to the WT from 7 DAP results in an increased amount of (1,3;1,4)-β-glucan (MLG) during the grain storage phase, which is followed by a decreased amount of starch and increased levels of glucose, sucrose, and total fructans. Early changes in carbohydrate biosynthesis allocation appear to influence endosperm transfer cell (ETC) differentiation and subsequently perturb sucrose uptake in the endosperm. (B) Consequently, high amounts of sucrose and fructans are accumulated in the grain cavity, causing the cavity to aberrantly expand and subsequent rupture (as indicated by the dotted line). Thinner cell walls in the non-uniformly developed ETCs of transgenic grain and variations in mannan labelling may contribute to ETC rupture in transgenic grain. (C) The transgenic grain has an elongated aleurone layer compared with the WT grain which persisted to maturity. As the grain matures, fluid in the transgenic cavity dries out, causing the grain to become shrunken. High levels of MLG and low levels of starch persist in the mature endosperm. Abbreviations: aleurone (al), cavity (c), endosperm (e), endosperm transfer cells (etc), nucellar projection (np), pericarp (p), peripheral endosperm (pe). Red arrows indicate probable osmotic pressure exerted from the cavity towards the endosperm. Grey boxes indicate findings at the genetic and metabolic level, while blue boxes indicate findings at the morphological level. Dark grey boxes highlight the mature phenotype. Arrangement of boxes roughly reflects observation time during the course of grain development.