AUXIN DEPRIVATION INDUCES SYNCHRONOUS GOLGI DIFFERENTIATION IN SUSPENSION-CULTURED TOBACCO BY-2 CELLS

To date, the lack of a method for inducing plant cells and their Golgi stacks to differentiate in a synchronous manner has made it difficult to characterize the nature and extent of Golgi retailoring in biochem ical terms. Here we report that auxin deprivation can be used to induc e a uniform population of suspension-cultured tobacco (Nicotiana tabac um cv BY-2) cells to differentiate synchronously during a 4-d period. Upon removal of auxin, the cells stop dividing, undergo elongation, an d differentiate in a manner that mimics the formation of slime-secreti ng epidermal and peripheral root-cap cells. The morphological changes to the Golgi apparatus include a proportional increase in the number o f trans-Golgi cisternae, a switch to larger-sized secretory vesicles t hat bud from the trans-Golgi cisternae, and an increase in osmium stai ning of the secretory products. Biochemical alterations include an inc rease in large, fucosylated, mucin-type glycoproteins, changes in the types of secreted arabinogalactan proteins, and an increase in the amo unts and types of molecules containing the peripheral root-cap-cell-sp ecific epitope JIM 13. Taken together, these findings support the hypo thesis that auxin deprivation can be used to induce tobacco BY-2 cells to differentiate synchronously into mucilage-secreting cells.