Plant Molecular Biology 38: 929–943, 1998.
© 1998 Kluwer Academic Publishers. Printed in the Netherlands.
Arabidopsis thaliana contains a large family of germin-like proteins:
characterization of cDNA and genomic sequences encoding 12 unique
Clay Carter, Richard A. Graham and Robert W. Thornburg
2212 Molecular Biology Building, Department of Biochemistry and Biophysics, Iowa State University Ames,
IA 50011, USA (
author for correspondence)
Received 17 March 1998; accepted in revised form 25 April 1998
Key words: germin, germin-like proteins, oxalate oxidase, multigene family, Arabidopsis thaliana
We have identiﬁed 39 Arabidopsis thaliana ESTs encoding germin-like proteins (GLPs) and have completely
sequenced 25 of these cDNAs. Our analysis demonstrates that the Arabidopsis genome contains a gene family with
at least 12 GLP genes. Comparisons with other known germins and germin-like proteins indicate that these Ara-
bidopsis GLP subfamilies are unique from wheat germin. All other known GLPs fall into one of these subfamilies.
The translated GLPs show approximately 35% amino acid identity with other GLPs outside of their subfamily and
signiﬁcantly higher levels of identity within their respective subfamily. The 3
ends of many of the GLP cDNAs are
heterogeneous and several sites of polyadenylation are used. Ten of the GLPs have N-terminal signal sequences
and most appear to be exported from the cell. Structurally, the GLPs are predicted to have a high content of β-
pleated sheet. Seven conserved regions of β-sheet were found in each of the GLP proteins along with α-helices
located at both N- and C-termini. These same structural elements are also conserved in wheat germin. With one
exception, all GLP family members contain at least one N-glycosylation site. All of these sites are conserved in
an unstructured loop between β-1 and β-2. Genes for two of these GLPs were identiﬁed in genomic sequences
previously deposited in the GenBank. The GLP3b gene is physically linked to the polyubiquitin 4 gene. The 3
of the GLP3b mRNA is only 0.5 kb from the ubq4 start of transcription. Analysis of the GLP3b promoter shows
the presence of a single putative auxin-response sequence located at −124 to −111 upstream from the 5
the GLP3b mRNA. The GLP9 gene was identiﬁed in an Arabidopsis contig from Chromosome 4.
Abbreviations: GLPs, germin-like proteins; ABRC, Arabidopsis Biological Resource Center at The Ohio State
University (arabidopsis + @osu.edu).
is a 130 kDa homopentameric protein 
ﬁrst detected in germinating cereals. Later, this protein
was found to be present in cereal cell walls, and still
later by combined analysis of its genetic coding ele-
ments and assay of its possible activity was found to
be an enzyme: oxalate oxidase (for review, see ).
Journal Paper No. J-17352 of the Iowa Agriculture and Home
Economics Experiment Station, Ames, Iowa. Project No. 3340.
Germin is expressed primarily in germinating embryos
Proteins with sequence identity to germins have
been identiﬁed from wheat  as well as from other
plant species. The expression of these germin-likepro-
teins (GLPs) varies widely among plant species. In
Sinapis alba, a germin-like protein, SaGLP, is ex-
pressed in a circadian oscillation in the epidermis and
spongy parenchyma of young leaves . This accu-
mulation occurs in the extracellular spaces and when
the primary cell wall material is lost, the SaGLP is