Fungal pathogens cause extensive plant diseases that damage crop
production in the agricultural industry, resulting in annual crop loss,
diminished food security, and historically significant epidemics. Though
effective fungicides are available, their risks to the environment and
animal health have increased the demand for more sustainable methods to
control fungal pathogens. In plants, polygalacturonic-inhibiting
proteins (PGIPs) play critical roles for resistance to fungal disease by
inhibiting the pectin-depolymerizing activity of endopolygalacturonases
(PGs), one type of enzyme secreted by pathogens that compromise plant
cell walls and leave the plant susceptible to disease. Here, the
interactions between PGIPs from Phaseolus vulgaris (PvPGIP1 and PvPGIP2)
and PGs from Aspergillus niger (AnPG2), Botrytis cinerea (BcPG1, BcPG2),
and Fusarium moniliforme (FmPG3) were reconstituted through a yeast two
hybrid (Y2H) system to investigate the inhibition efficiency of various
PvPGIP1 and 2 truncations and mutants. We found that tPvPGIP2_5-8,
which contains LRR5 to LRR8 and is of only one-third the size of the
full-length peptide, exhibits the same level of interactions with AnPG
and BcPGs as the full length PvPGIP2 via Y2H. The inhibitory activities
of tPvPGIP2_5-8 on the growth of A. niger were then examined and
confirmed on pectin agar. Application of both full length PvPGIP2 and
tPvPGIP2_5-8 clearly slows down the growth of A. niger and B. cinerea
in the presence of pectin. The investigation on the sequence-function
correlation of PvPGIP2 suggests that LRR5 could have the most essential
structural feature for the inhibitory activities, and may be a possible
target for the future engineering of PGIP with enhanced activity. This
work highlights the potential of using plant-derived PGIPs as an
exogenously applied fungal control agent both to plants and postharvest
crops while minimally impacting the environment and human health.
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