Abstract :
Ten acidic and eight basic pathogenesis-related (PR) proteins
were induced in primary leaves of Phaseolus vulgaris
cv. Pinto following infection with southern bean mosaic
virus (SBMV), a virus that induces circular, brown necrotic
local lesions. These PR proteins included: four, 17
kDa, serologically related, acidic proteins of unknown
functions; two chitinases, one acidic (29 kDa) and one
basic (32 kDa) possessing antifungal activities; and four
(21 kDa, 28 kDa, 29 kDa, 36 kDa) serologically related,
acidic glucanases. The production of PR proteins was
minimal during the period of active SBMV multiphcation;
greatest increase of PR proteins occurred after
SBMV had reached a maximum level. Several of these
PR proteins, including the 29 kDa acidic chitinase and
two acidic glucanases (21 kDa and 36 kDa) accumulated
in the intercellular space fluid. Similar PR proteins were
synthesized in Pinto bean primary leaves infects with any
of three other viruses that formed lesions of divergent
phenotypes. However, the proportion of some of the PR
proteins in the various lesion-types differed considerably.
These results indicate that PR proteins play no active
role in viral localization or inactivation and that their
production is a metabolic adjustment to endogenous
stress
