We report the generation of Solanum tuberosum transformants
expressing Cicer arietinum βIII-Gal. βIII-Gal is a
β-galactosidase able to degrade cell wall pectins during cell
wall loosening that occurs prior to cell elongation. cDNA
corresponding to the gene encoding this protein was identified
among several chickpea β-galactosidase cDNAs, and
named CanBGal-3. CanBGal-3 cDNA was expressed in
potato under the control of the granule-bound starch
synthase promoter. Three βIII-Gal transformants with varying
levels of expression were chosen for further analysis.
The transgenic plants displayed no significant altered phenotype
compared to the wild type. However, β-galactanase
and β-galactosidase activities were increased in the transgenic
tuber cell walls and this affected the potato tuber
pectins. A reduction in the galactosyl content of up to 50%
compared to the wild type was observed in the most
extreme transformant, indicating a reduction of 1,4-β-
galactan side-chains, as revealed by analysis with LM5 specific
antibodies. Our results confirm the notion that the
pectin-degrading activity of chickpea βIII-Gal reported in
vitro also occurs in vivo and in other plants, and confirm
the involvement of βIII-Gal in the cell wall autolysis process.
An increase in the homogalacturonan content of transgenic
tuber cell walls was also observed by Fourier
transform infrared spectroscopy (FTIR) analysis.
