3.10 BPH infestation activated defense-related phytohormones
pathways though dynamic m6A modifications
We investigated whether anti-herbivore defense hormones JA and SA
metabolic pathways are regulated by m6A modification
and whether the expression profiles of their metabolic genes are altered
by BPH infestation in rice. All 9 selected biosynthesis genes in the
JA pathway, except downregulatedOsLOX5 , were upregulated
in BPH-infested
plants (Figure 5a). Expression
levels of all the JA-responsive genes, OsPR5-1 , OsPR10 ,
and OsRbohC-F , were downregulated in BPH-infested samples; the
remaining genes, apart from non-regulated OsWRKY10 , were
significantly upregulated (Figure 5b,c).
Among the JA biosynthesis genes,OsAOS2 , OsJMT1 , and OsLOX8only exhibited
upregulated
differential m6A
sites; OsAOS1 , OsLOX2 , and OsLOX5 exhibited both
up-, and down-directed m6A sites
(Supporting Information: Table S15,
S16). For JA-responsive genes, OsPR2 , OsPR5-2 ,OsPR5-3 , OsPR5-4 , OsMYB2 , and OsWRKY28 only
contained up-directed differential
m6A sites, while OsPR5-1 , OsPR10 ,OsRbohD , and OsRbohF only showed down-directed
differential m6A sites. OsRbohB ,OsRbohC , and OsRbohE contained both up- and down-directed
m6A sites (Supporting Information: Table S15, S17).
Most upregulated genes showed a positive correlation with the
up-directed m6A modification positions, such asOsJMT1 , OsAOS1 , OsAOS2 , and OsLOX8 in
biosynthesis genes, andOsPR2 , OsPR5-2 ,OsPR5-3 , OsPR5-4 ,OsMYB2 , and OsWRKY28 in
responsive genes. Both
m6A modification and the relative expression ofOsPR5-1 , OsPR10 , OsLOX5 , and OsRbohC-F were
significantly downregulated in
BPH-infested
plants (Figure 5a-c; Supporting
Information: Table S15-17).
In the SA pathway, all candidate
biosynthesis-related genes were
upregulated in
BPH-infested samples
(Figure S12a). Among the
response-related genes, OsPR1-12 , OsPR1-51 , OsPR1a ,OsPR1b , and OsWRKY4 5 were upregulated, whileOsPR1-21 , andOsPR1-101 were downregulated
in BPH-infested samples (Figure S12b). Regarding the
m6A position direction, OsCM andOsWRKY45 only exhibited up-directed differential
m6A sites; OsICS1 and OsPR1-101contained down-directed differential m6A sites; andOsEDS1 , OsPAL , and OsPAL1 showed both up- and
down-directed m6A sites (Supporting Information: Table
S15, S18, S19). The m6A modification level of SA
pathway-related genes also showed a positive correlation with
transcriptional regulation. The genes that followed such pattern
included OsPAL1 and OsCM in the biosynthesis genes andOsPR1-101 and OsWRKY45 in the responsive genes (Supporting
Information: Figure S12; Table S15, S18, S19). However, the proportion
of m6A modified genes was lower than that of the JA
pathway-related genes.
BPH infestation successfully induced phytohormones accumulation in
plants. This degree of induction was more
pronounced for JA production than for
SA (Figure 5d,e; Supporting Information: Figure S12c), which validated
the RT-qPCR and transcriptome data of the related transcripts. These
were accompanied by dynamic m6A methylation
modification and gene expression changes in major hormonal
pathway-related genes, especially in genes related to the JA metabolic
pathway.