| Literature References | 1. RUIZ-MEDRANO, R., JIMENEZ-MORAILA, B., HERRERA-ESTRELLA, L. AND
RIVERA-BUSTAMANTE, R.F.
Nucleotide sequence of an osmotin-like cDNA induced in tomato during viroid
infection.
PLANT MOL.BIOL. 20(6) 1199-1202 (1992).
2. EDENS, L., HESLINGA, L., KLOK, R., LEDEBOER, A.M., MAAT, J., TOONEN, M.Y.
VISSER, C. AND VERRIPS, C.T.
Cloning of cDNA encoding the sweet-tasting plant protein thaumatin and its
expression in Escherichia coli.
GENE 18(1) 1-12 (1982).
3. SINGH, N.K., NELSON, D.E., KUHN, D., HASEGAWA, P.M. AND BRESSAN, R.A.
Molecular cloning of osmotin and regulation of its expression by ABA and
adaption to low water potential.
PLANT PHYSIOL. 90(3) 1096-1101 (1989).
4. REBMANN, G., MAUCH, F. AND DUDLER, R.
Sequence of a wheat cDNA encoding a pathogen induced thaumatin-like protein.
PLANT MOL.BIOL. 16(6) 1089-1091 (1991).
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| Documentation | Pathogenesis related (PR) proteins, which are induced by various agents
ranging from ethylene to pathogens, are structurally diverse and apparently
ubiquitous in plants [1]: they include thaumatin, osmotin, tobacco major
and minor PR proteins, alpha-amylase/trypsin inhibitor, and P21 and PWIR2
soybean and wheat leaf proteins. The proteins are involved in systematically
acquired resistance and stress response in plants, although their precise
role is unknown [1]. Thaumatin is an intensely sweet tasting protein
(about 100,000 times sweeter than sucrose [2]) found in the West African
shrub Thaumatacoccus danielli: it is induced by attack by viroids, which
are single-stranded unencapsulated RNA molecules that do not code for
protein. Like other PR proteins, thaumatin is predicted to have a mainly
beta structure, with a high content of beta-turns and little helix [1].
Tobacco cells exposed to gradually increased salt concentrations develop a
greatly increased tolerance to salt, due to the expression of osmotin [3],
a member of the PR protein family. Wheat plants attacked by barley powdery
mildew express a PR protein (PWIR2), which results in resistance against
that infection [4]. The similarity between this and other PR proteins to
the maize alpha-amylase/trypsin inhibitor has suggested that PR proteins
may act as some form of inhibitor [4].
THAUMATIN is a 6-element fingerprint that provides a signature for
thaumatin and pathogenesis-related proteins. The fingerprint was derived
from an initial alignment of 6 sequences: the motifs were drawn from
conserved regions spanning the full alignment length, motif 4 including the
region encoded by PROSITE pattern THAUMATIN (PS00316), which contains 3
Cys residues known to be involved in disulphide bond formation. Two
iterations on OWL22.1 were required to reach convergence, at which point
a true set comprising 22 sequences was identified. Two partial matches
were also found, both of which are osmotin-like proteins that fail to make
significant matches with motifs 2 and 4.
An update on SPTR37_9f identified a true set of 32 sequences, and 22
partial matches.
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