Effects of Yariv dyes, arabinogalactan-protein binding reagents, on the growth and viability of Brazilian pine suspension culture cells

Abstract

Arabinogalactan-proteins (AGPs) are a family of highly glycosylated hydroxyproline-rich glycoproteins implicated in several aspects of plant growth and devel- opment. (b-D-glucosyl)3 Yariv phenylglycoside (b-GlcY), commonly known as Yariv reagent, selectively binds AGPs. We treated cell suspension cultures of Araucaria angustifolia, the Brazilian pine, with b-GlcY and observed inhibition of biomass increase in a culture medium with 50 lM b-GlcY. However, the growth was not inhibited by (a-D-galactosyl)3 Yariv phenylglycoside (a-GalY) which does not bind AGPs. Fluorescein diacetate staining of cells indicated that b-GlcY severely affected cell viability. However, cell swelling, bursting and release of cellular contents, all characteristics of necrotic cell death, were not observed in b-GlcY-treated cells. Instead, programmed cell death (PCD) structural changes such as cytoplasmic shrinkage and condensation were observed in b-GlcY- treated cells. In addition, callose accumulation, which is another marker of PCD, was also observed in b-GlcY- treated cells. The use of both, Ac-VEID-CHO, an inhibitor of caspase-like proteolytic activity related to PCD, and phenyl methyl sulphonyl fluoride (PMSF), a protease inhibitor known to suppress PCD, in the culture medium did not reverse the growth inhibition caused by b-GlcY. These data indicate that the b-GlcY-induced inhibition of Araucaria cell's growth is related to AGP perturbation, and also that this growth inhibition is due to increased cell death not driven by necrosis.