Abstract:
Freezing is a major
environmental stress, which limits plant’s
distribution, growth and productivity. Ice
nucleation active bacteria can catalyze ice
formation at temperatures as high as -2°C. A
membrane protein confer the ability of ice
nucleation, called ice-nucleating proteins
(INPs), which is encoded by a single gene.
Mutation in this gene will lead to delaying
of ice nucleation. In this study, leaf tissues
of several plants with freezing symptoms
were collected from different locations and
40 bacterial isolates with yellow circular
colonies and regular margins were isolated
from samples. Finally, total of 12 isolates
belong to Xanthomonas were selected for
ice nucleate activity (INA) by Dropletfreezing
test and presence of INA gene was
surveyed by PCR. According to the
obtained results, isolate 28 was targeted to
mutagenesis by using Tn5 transposon. After
mutagenesis, isolates with ability to grow on
kanamycin, which lack of INAx gene in
PCR were considered as mutated isolates
and their freezing effects were evaluated on
bean seedlings. Results showed that isolates
with mutated INA gene cannot induce
freezing on bean seedlings, while primary
identified isolate (isolate 28) could do it.
These results show that if we could replace
wild type ice nucleation active bacteria with
mutated forms (just different in ice
nucleation activity), we could, probably,
prevent freezing and subsequent economic
losses.
