Reference "Evolution and differential expression of the (1-->3)-beta-glucan endohydrolase-encoding gene family in barley, Hordeum vulgare"

Reference ID

8623

Title

Evolution and differential expression of the (1-->3)-beta-glucan endohydrolase-encoding gene family in barley, Hordeum vulgare

Source

Gene, 1992, vol. 120, pp. 157-165

Authors (3)

Xu-P	Wang-J
Fincher-G-B

Abstract

The (1-->3)-beta-D-glucan glucanohydrolases [(1-->3)-GGH; EC 3.2.1.39] of barley
(Hordeum vulgare L., cv Clipper) are encoded by a small gene family. Amino acid
sequences deduced from cDNA and genomic clones for six members of the family
exhibit overall positional identities ranging from 44% to 78%. Specific DNA and
oligodeoxyribonucleotide (oligo) probes have been used to demonstrate that the
(1-->3)-GGH-encoding genes are differentially transcribed in young roots, young
leaves and the aleurone of germinated grain. The high degree of sequence
homology, coupled with characteristic patterns of codon usage and insertion of a
single intron at a highly conserved position in the signal peptide region,
indicate that the genes have shared a common evolutionary history. Similar
structural features in genes encoding barley (1-->3,1-->4)-beta-glucan 4-
glucanohydrolases [(1-->3,1-->4)-GGH; EC 3.2.1.73] further indicate that the (1-->3)-
GGHs and (1-->3,1-->4)-GGHs are derived from a single 'super' gene family, in
which genes encoding enzymes with related yet quite distinct substrate
specificities have evolved, with an associated specialization of function. The
(1-->3,1-->4)-GGHs mediate in plant cell wall metabolism through their ability
to hydrolyse the (1-->3,1-->4)-beta-glucans that are the major constituents in
barley walls, while the (1-->3)-GGHs, which are unable to degrade the plant (1-->3,1-->4)-beta-
glucans, can hydrolyse the (1-->3)- and (1-->3,1-->6)-beta-glucans of fungal
cell walls.