Identification of a peroxidase gene negatively regulating rice
resistance to blast disease
Among the 321 core genes, a peroxidase gene, Os07g0677200, drew
our attention, with the highest FPKM value at 12 hpi of M. oryzaein Nipponbare and the second highest FPKM value in Hui1586 (Supplemental
dataset 7). To test the function of Os07g0677200 (hereby namedPerox4 following the names of published peroxidase genes in rice)
in rice blast disease resistance, we used CRISPR/Cas9 technology to
knock out the Perox4 gene in the rice cultivar Zhonghua 11
(ZH11). Japonica rice ZH11 is moderately susceptible to M. oryzaeisolate Guy11 and has been used in a large-scale gene knockout project
in our group. A 20-nt sequence in the third exon of the Perox4gene was designed as the target site for Cas9 cleavage, and multiple
putative transgenic lines were generated and verified by sequencing. We
found one line (named perox4-1 ) carrying a one-base insertion in
the target site that truncates the Perox4 open reading frame, and
another line (named perox4-2 ) carrying a three-base deletion in
the Perox4 gene (Fig. S3A).
The perox4 lines were challenged with the blast isolate Guy11. We
found that the lesion numbers and lesion size were dramatically reduced
in the perox4 lines compared with ZH11 (Figs. 8A and 8B).We then measured the expression of defense-related genes, such asOsPR4 and OsPR 5, in perox4 and ZH11 plants withM. oryzae infection using qRT-PCR. We observed that the
expression levels of these marker genes were elevated in perox4compared with ZH11 plants (Fig. 8C). Together, these results
demonstrated that the Perox4 negatively regulated rice resistance
to M. oryzae.