A novel tetrasaccharide, with a structure similar to the terminal sequence of an arabinogalactan-protein, accumulates in rice anthers in a stage-specific manner

Abstract

Analysis of free sugars in developing rice anthers by high-performance anion-exchange chromatography (HPAEC) showed that a very high concentration of a novel oligosaccharide accumulated specifically during microsporogenesis. Structural analysis of the purified oligosaccharide by methylation analysis, mass spectrometry/mass spectrometry (MS/MS), and nuclear magnetic resonance (NMR) spectroscopy revealed its structure to be β-L-Araf-(1→3)-α-L-Ara f-(1→3)-β-D-Galp-(1→6)-D-Gal, which is closely related to a tetrasaccharide unit found in the glycan chain of a plant cell surface proteoglycan, the arabinogalactan-protein (AGP). Chilling treatment (12°C, 4 days), which injures rice anthers during microsporogenesis, decreased the concentration of the tetrasaccharide, but the sucrose level increased. This effect was especially evident in a chilling-sensitive mutant line, YM56-1. These results suggest that this unique tetrasaccharide may play an important role in both the development of the rice anther and its response to chilling.