3.9 BPH infestation altered the expression and m6A modification of cellulose synthesis-related genes
Both Bph30 and Bph40genes were significantly upregulated upon BPH infestation (Figure 4a). Therefore, the potential correlation between m6A levels and the expression of rice genes involved in cellulose and hemicellulose synthesis was analyzed. Among thirteen candidate cellulose synthesis genes which containing m6A modification sites, eight genes were upregulated in BPH-infested plants (Figure 4b). Moreover, there were total 39 up- and 23 down-directed differential m6A modification positions among the 13 cellulose synthesis genes, 5 of which showed up-trending m6A methylation, that is, the number of up-directed m6A sites was higher than that of down-directed m6A sites (Supporting Information: Table S11, S13). m6A modifications and the relative expression of genes in cellulose synthesis were positively correlated, suggesting that m6A modification is largely involved in the synthesis of cellulose. Additionally, four of the six hemicellulose synthesis (CSLF4 , CSLHl ,IRX10 , and IRX14 ) were upregulated, while IRX9 was downregulated in BPH-infested plants (Figure 4c). However, only four genes (CSLF2 , CSLHl , IRX9 , and IRX14 ) were detected with m6A positions (Supporting Information: Table S11, S14) and no fixed regular patterns were found.
Moreover, the contents of cellulose and hemicellulose were measured. BPH infestation induced cellulose and hemicellulose accumulation in rice. This degree of induction was more pronounced for cellulose accumulation than for hemicellulose (Figure 4d,e), which were validated the RT-qPCR and transcriptome data. Taken together, BPH infestation activated the expression and m6A modification of cellulose but not apparent in hemicellulose synthesis-related genes, and was more prominent in cellulose synthesis.