Summary
mi
RNA
s contribute to plant resistance against pathogens. Previously, we found that the function of miR398b in immunity in rice differs from that in Arabidopsis. However, the underlying mechanisms are unclear.
In this study, we characterized the mutants of miR398b target genes and demonstrated that multiple superoxide dismutase genes contribute to miR398b‐regulated rice immunity against the blast fungus
Magnaporthe oryzae
.
Out of the four target genes of miR398b, mutations in
Cu/Zn‐Superoxidase Dismutase1
(
CSD
1
),
CSD
2
and
Os11g09780
(
Superoxide DismutaseX
,
SODX
) led to enhanced resistance to
M. oryzae
and increased hydrogen peroxide (H
2
O
2
) accumulation. By contrast, mutations in
Copper Chaperone for Superoxide Dismutase
(
CCSD
) resulted in enhanced susceptibility. Biochemical studies revealed that
csd1
,
csd2
and
sodx
displayed altered expression of
CSD
s and other superoxide dismutase (
SOD
) family members, leading to increased total
SOD
enzyme activity that positively contributed to higher H
2
O
2
production. By contrast, the
ccsd
mutant showed
CSD
protein deletion, resulting in decreased
CSD
and total
SOD
enzyme activity.
Our results demonstrate the roles of different
SOD
s in miR398b‐regulated resistance to rice blast disease, and uncover an integrative regulatory network in which miR398b boosts total
SOD
activity to upregulate H
2
O
2
concentration and thereby improve disease resistance.