Soluble and bound hydroxyproline-rich glycoproteins in control and wounded oat and barley primary leaves

Abstract

The partitioning of hydroxyproline-rich glycoprotein (HRGP) was determined between the apoplast and symplast of control and wounded six-day-old barley ( Hordeum vulgare) and oat ( Avena sativa) primary leaves. In controls, from 5% (barley) to 9% (oat) of the total HRGP was soluble or weakly ionically bound within the apoplast, 32% (barley) to 35% (oats) was symplastic and soluble in 50 mH K-Pi buffer, no HRGP was released by extracting washed cell wall preparations with 1 M NaCl, and about 60% of the HRGP was covalently bound to the cell wall in either species. Wounding dicot seedlings normally causes marked HRGP induction; in contrast, wounding barley or oat leaves 24 hr before sampling had no appreciable efrect on HRGP levels or localization, but apoplastic peroxidase activity increased markedly. These results suggest that HRGP may play an important role in dicots, but not in cereals such as oats and barley, as a defensive response to tissue damage.