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

Abstract

We examined a novel rice mutant, Fukei 71 (Oryza sativa L.), for alterations in the levels of hydroxycinnamoyl esters that are linked to cell wall polysaccharides and lignin units. In this mutant, a recessive mutation at a single 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 Mäule reaction, which is specific for syringyl 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 antibodies specific for phenylalanine ammonia-lyase (PAL) revealed higher levels of PAL in the abnormal parenchyma tissue of Fukei 71 than in the parenchyma tissue of the parent cultivar Fujiminori. These results and the observation that PAL was produced at a greatly elevated level indicated that the phenylpropanoid pathway that leads to the biosynthesis of polysaccharide-linked FA and PCA was abnormally activated in the irregularly shaped and collapsed internode parenchyma cells, in which the biosynthesis of lignin is normally repressed.

Transcription profiling identifies candidate genes for secondary cell wall formation and hydroxycinnamoyl-arabinoxylan biosynthesis in the rice internode

“…Most CesA genes were significantly down-regulated, which is consistent with a previous report that the cell walls of F71 pith parenchyma have a 25% reduction in glucose that is presumably derived from cellulose (Nishikubo et al 2000). Furthermore, β-xylosidase was downregulated, leading to the accumulation of 1,4-β-dxylan, and UDP-xylose 4-epimerase was up-regulated, leading to an increase in UDP-l-arabinose in the F71 pith parenchyma, which might be closely associated with the activation of AX synthesis in the F71 pith parenchyma.…”

“…When F71 is grown at a high temperature (25-30°C), it exhibits a dwarf phenotype and over-accumulates hydroxycinnamoyl-AX in irregularly shaped internode pith parenchyma cells Futsuhara 1981, 1982;Nishikubo et al 2000). All probe sets are listed in Table S3, and the top 15 probe sets are listed in Table 2 according to the fold changes in the normalized intensities.…”

“…Candidate genes related to secondary cell wall formation were examined in wildtype rice by comparing pith parenchyma cells without secondary cell walls and whole internodes containing cells with secondary cell walls. The rice dwarf mutant Fukei71 (F71) was previously isolated by gamma-ray irradiation, which has non-uniform internode pith parenchyma cells with abnormally thickened cell walls that contain large amounts of hydroxycinnamoyl-AX Futsuhara 1981, 1982;Nishikubo et al 2000). Recently, the F71 causal gene, D50, was found to encode an inositol polyphosphate 5-phosphatase and to possibly function in formation of intercalary meristem, including the direction of cell division, deposition of cell wall pectins and control of actin organization (SatoIzawa et al 2012).…”

Phenylalanine ammonia-lyase and cell wall peroxidase are cooperatively involved in the extensive formation of ferulate network in cell walls of developing rice shoots

“…A dwarf rice mutant that had irregularly shaped parenchyma cells contained a large quantity of cell wall-bound FA (Nishikubo et al, 2000). The mutant contained a higher level of PAL proteins compared to the wild strain.…”

A chickpea Kunitz trypsin inhibitor is located in cell wall of elongating seedling organs and vascular tissue

“…Lignin is stained purplish-red after the Mäule reaction, while brownish-yellow deposits are known as "negative reaction products" (Nishikubo et al 2000). Figure 6 shows that almost no lignin was present in 4-day-old epicotyl sections.…”