3.11 BPH infestation affected m6A modification
of genes involved in growth-related phytohormones pathways
The overall m6A methylation position in rice was
significantly attenuated by the BPH treatment (Figure 1f,g; Supporting
Information: S4). However, the defense-related pathways were activated
by BPH infestation which was accompanied by a large proportion of
upregulated transcripts and m6A methylation sites
(Figure 4, 5; Table S11, S15). Plant defense against herbivores is
costly and is often associated with growth repression (Deng et al.,
2020). We then explored m6A modification and
transcriptional regulation of genes involved in plant growth-related
phytohormones pathways especially auxin and gibberellin (GA).
Among the selected 32 genes
containing m6A modification sites, 11 up- and 79
down-directed m6A modification positions were present
in BPH-infested plants compared with those in the un-infected plants. A
total of 27 genes were found to have down-directed m6A
sites, among which 26 genes showed down-trending m6A
methylation; that is, the number of down-directed m6A
sites was higher than up-directed m6A sites
(Supporting Information: Table S20).
For transcriptome regulation, 27 of these 32 transcripts were
significantly downregulated in BPH-infested plants, 25 of which
displayed down-trending m6A methylation (Figure 6a-d,
Supporting Information: Table
S20-S22). This indicated a positive correlation between
m6A modifications and the expression of key genes
responsible for rice growth. In contrast, for the GA metabolic process,
three of the five candidate genes were upregulated in the BPH-infested
group. There were 9 up- and 5 down-directed m6A
modification positions in the BPH-infected plants compared to those in
the un-infected plants.
m6A modifications and gene expression were also
positively correlated (Figure 6e, Supporting Information: Table S20,
S22). The m6A modification levels of auxin pathway-
and GA biosynthesis-related genes were significantly attenuated under
BPH attack. This was accompanied by the downregulated expression of
these transcripts. Meanwhile, m6A modification was
involved in the activation of GA catabolism-related genes. Thus, rice
growth was restricted during BPH attack to optimize resource allocation
for plant defense though affecting m6A modification of
genes involved in defense- and growth-related phytohormones pathways.