Specific accumulation of polysaccharide-linked hydroxycinnamoyl esters in the cell walls of irregularly shaped and collapsed internode parenchyma cells of the dwarf rice mutant Fukei 71

We examined a novel rice mutant, Fukei 71 (Oryza sativa L.), for alteration s in the levels of hydroxycinnamoyl esters that are linked to cell wall pol ysaccharides and lignin units. In this mutant, a recessive mutation at a si ngle locus caused the collapse of parenchyma cells in the internodes. Light microscopy revealed that the abnormal walls of internode parenchyma cells of Fukei 71 were stained by the Maule reaction, which is specific for syrin gyl units in phenolic compounds. These walls were not stained by Wiesner's reagent (phloroglucinol-HCl), which reacts cinnamaldehyde in lignin. Levels of p-coumaric acid (PCA) and ferulic acid (FA) were apparently elevated in the abnormal tissue of the mutant. Western blotting analysis with antibodi es specific for phenylalanine ammonia-lyase (PAL) revealed higher levels of PAL in the abnormal parenchyma tissue of Fukei 71 than in the parenchyma t issue of the parent cultivar Fujiminori. These results and the observation that PAL was produced at a greatly elevated level indicated that the phenyl propanoid pathway that leads to the biosynthesis of polysaccharide-linked F A and PCA was abnormally activated in the irregularly shaped and collapsed internode parenchyma cells, in which the biosynthesis of lignin is normally repressed.