Irregular Deposition of Cell Wall Polymers Resulting from Defective Cellulose Synthase Complexes

The crystalline cellulose microfibril is formed by the spontaneous association of about 36 β-D-glucan chains, which are simultaneously synthesised by a large membrane-localised multi-enzyme cellulose synthase complex. Antisense technology has been previously employed separately on two of the constituent cellulose synthase catalytic subunits (CesA) of the complex in potato (Solanum tuberosum), namely CesA2 and CesA4, to generate potato tuber cell walls with reduced cellulose content. Genetic crossing of two transgenic potato lines csr2-1 and csr4-8 was carried out to investigate the effects of two defective CesAs in the same genetic background, with respect to cellulose deposition in the potato tuber cell walls. It was striking to observe, through fluorescence microscopy with calcofluor white, a strong fluorescence in the cell corners and less prominent and uneven fluorescence around the cells of the csr2 tubers as compared to others. It was also noted that these phenotypes were not pronounced in the csr2/csr4 double transformants as expected.