Lignin masks the presence of fibrillar network structure in the cell corner middle lamella (CCML)

Abstract

Abstract The presence of fibrillar structures (FS) in the cell corner middle lamella (CCML) regions was demonstrated in several species of plants. The FS in the CCML of bass wood, oak wood, and bamboo became clearly visible after removal of lignin by wood decay fungi. The occurrence of FS in the CCML was also confirmed by examining early stages of cell wall formation in silver poplar, Japanese red pine, Arabidopsis and alfalfa. The fibrillar texture became increasingly less defined with the onset of lignification as the interfibrillar spaces were masked by lignin polymers and the fibrillar network became embedded within the lignin matrix. The FS stained positively with PATAg and ruthenium red, which is interpreted to be an indicator of the presence of structural polysaccharides (non-cellulosics and pectins). Our work demonstrated that fibrillar network is a characteristic feature of CCML of plant cell walls that is clearly visible prior to lignification of this cell wall region, but becomes invisible after the deposition of lignin.