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stems and petioles (Del Campillo and Lewis. 1992; Eynl
cr
01..
1993).
In
inflorescences PR-proteins
are
detected in sepals, pedicels, anthers. pistils, stigmata
and ovaries (Van Loon, 1999; Buchel and Linthorst. 1909). In seeds of ~naize.
sorghum, oat. barley, and wheat a group of PR-proteins is established commonly
named permatins, characterized as PR-5 (Vigers
et
01..
1991).
2.2.3. Induction of PR-proteins
Besides the known PR inducers of biotic origin viz.. pathogens, insects.
nematodes and herbivores (Fidantsef
el
01.. 1999; Van Loon. 1999; Rohert
et
ul..
2001: Reiss m d Horstmann, 2001; Schultheiss
er
al..
2003b). a new type of biotic
inducers. Orobunche weeds, also has been reported in tobacco (Joel and Portnoy,
1998). Pathogen-derived elicitors are potent PR-protein inducers. Well-characterized
elicitor includes glucan and chitin fragments derived from fungal cell walls, fungus-
secreted glycoproteins, peptides and proteins of elicitin family (Miinch-Garthoff
er
ul., 1997; HonCe
er
ul., 1998; Zhou, 1999; Kombrink
er
ul.. 2001; Edreva
et
ul.,
2002). Protein products of avirulence genes in fungi and bacteria
are
capable of
inducing PR-proteins (Staskawicz et
ul.,
1995; Hennin
et
ul.,
2001). Cell wall splitting
enzymes, such as polygalacturonases induced the accumulation of PR-proteins
(Pierpoint et ul., 1981). It has been shown that polygalacturonases release biologically
active pectic fragments from plant cell walls, named endogenous elicitors (Mc Neil
el
01..
1984). capable of inducing a set of defense responses in plants, including the
accumulation of PR-proteins (Boudart
el
ul., 1998).
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