Reduced CHH methylation levels reveal a critical role of aging pathway genes in Moso bamboo flowering

Moso bamboo holds significant economic importance in China, serving various purposes, such as food, material, ornamentation, and greenery. Despite its versatility, the occurrence of flowering in Moso bamboo poses a threat to bamboo forests, resulting in substantial losses. The underlying cause of bamboo flowering remains elusive. Dynamic fluctuations in DNA methylation govern the transcriptional levels of crucial genes pivotal for plant growth and development. In this study, we conducted comprehensive DNA methylation (by whole-genome bisulfite sequencing) and transcriptome (by RNA-seq) analyses on non-flowering leaves, flowering leaves, and spikelets of Moso bamboo. Our findings revealed a notable reduction in the overall DNA methylation level, particularly CHH methylation, from leaves to spikelets, influencing the expression of differentially regulated genes. Notably, we identified DNA methylation as a regulatory mechanism for numerous flowering-related genes, including SPLs, FT, and SOC1. Specifically, the SPL3f gene, a key regulator of the aging pathway, exhibited hypomethylation and a high expression level in spikelets. Conversely, SOC1c displayed transcriptional silencing attributed to hypermethylation in the CHH context in the leaves of non-flowering plants. DNA methylation may affect the flowering mechanism of Moso bamboo by regulating the expression of key genes. In summary, our results shed light on the dynamic changes in DNA methylation between leaves and spikelets, unraveling an important epigenetic modification mechanism for flowering in Moso bamboo.