DNA methylation profile revealed the dynamically epigenetic regulation of the distinct heteromorphic leaf development in Populus euphratica

The heteromorphic leaves of Populus euphratica are typically an adaptive trait in reaction to the dry desert surroundings. The involvement of DNA methylation in plant organ development and response to the environment is well-established. Nevertheless, there is still limited understanding regarding the specific regulatory processes governing DNA methylation during the formation and adjustment of heteromorphic leaves in P. euphratica. Here, the comprehensive DNA methylation landscape for 90 samples across two growth stages in P. euphratica was presented for the first time. In combination with the corresponding mRNA transcriptomes, insights into the epigenetic regulation of heteromorphic leaves were brought to light. It was observed that linear and lanceolate leaves demonstrated an increase in DNA methylation compared with ovate and broad-ovate leaves, and DNA methylation gradually decreased with leaf ripening. Additionally, methylation regulated the expression of specific genes related to leaf structure and function, such as CUS2 and Rab-H1b, indicating a mechanism for enhancing adaptability. The auxin hormone signaling pathway was closely linked to the formation of heteromorphic leaves, and alterations in the transcript levels of auxin response factor were tightly regulated by DNA methylation. This research expands the knowledge of epigenetic mechanisms involved in the formation of heteromorphic leaves, and thus could contribute to further studies on the adaptive evolution in P. euphratica.