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Charcterisation of two tomato fruit-expressed cDNAs encoding xyloglucan endo-transglycosylase

Arrowsmith, D.A., De Silva, J.
Plant molecular biology 1995 v.28 no.3 pp. 391-403
Solanum lycopersicum var. lycopersicum, complementary DNA, transferases, xyloglucans, multigene family, nucleotide sequences, amino acid sequences, ripening, enzyme activity, messenger RNA, gene expression
Xyloglucan endo-transglycosylase (XET) catalyses the cleavage and concomitant transfer of one xylo-glucan molecule to another. It is thought to be an important component of cell wall metabolism, particularly in expanding tissue and ripening fruits. The recently reported cloning of a cDNA encoding a seed-expressed XET from nasturtium has enabled two XET-encoding cDNAs to be isolated from tomato fruit (breaker stage) cDNA library. Their deduced amino acid sequences exhibit ca. 40% identity to nasturtium XET. One of the tomato cDNA clones (tXET-B2) was over-expressed in Escherichia coli; following purification and refolding, the recombinant protein was shown to have XET activity with no detectable hydrolytic activity. Southern hybridisation analysis suggests that these clones are members of a small multi-gene family encoding tomato XET. Ribonuclease protection assays show that transcripts protected by one of the clones (tXET-B1) are most abundant in pink fruit pericarp and were also detected in stems.