Bg. Lane et al., GERMIN, A PROTEIN MARKER OF EARLY PLANT DEVELOPMENT, IS AN OXALATE OXIDASE, The Journal of biological chemistry, 268(17), 1993, pp. 2239-2242
Germin is a homopentameric glycoprotein, the synthesis of which coinci
des with the onset of growth in germinating wheat embryos. There have
been detailed studies of germin structure, biosynthesis, homology with
other proteins, and of its value as a marker of wheat development. Ge
rmin isoforms associated with the apoplast have been speculated to hav
e a role in embryo hydration during maturation and germination. Antige
nically related isoforms of germin are present during germination in a
ll of the economically important cereals studied, and the amounts of g
ermin-like proteins and coding elements have been found to undergo con
spicuous change when salt-tolerant higher plants are subjected to salt
stress. In this report, we describe how circumstantial evidence arisi
ng from unrelated studies of barley oxalate oxidase and its coding ele
ments have led to definitive evidence that the germin isoform made dur
ing wheat germination is an oxalate oxidase. Establishment of links be
tween oxalate degradation, cereal germination, and salt tolerance has
significant implications for a broad range of studies related to devel
opment and adaptation in higher plants. Roles for germin in cell wall
biochemistry and tissue remodeling are discussed, with special emphasi
s on the generation of hydrogen peroxide during germin-induced oxidati
on of oxalate.