Deciphering the Regulatory Mechanism of PmMYB21 in Early Flowering of Prunus mume through Dap-Seq and WGCNA Analysis

Abstract

Prunus mume Siebold & Zucc (mei) is a horticulturally important fruit tree that undergoes anthesis in winter. Therefore, its flowering process is challenged by low-temperatures conditions. The transcription factor (TF) MYB21 is pivotal in regulating the flowering process, and particularly functions in petal expansion and filament elongation. However, the regulatory mechanism of PmMYB21 in mei remains unknown. To breed early-flowering cultivars, a deeper understanding of PmMYB21-regulated genes is essential. We employed DNA affinity purification sequencing (Dap-seq) to identify downstream genes bound by PmMYB21. The results revealed the promoter region is the primary binding region of PmMYB21, and the AGTTAGGTARR motif (motif1) is the predominant binding sequence type. Our analysis identified 8533 genes that are potentially bound by PmMYB21 with the motif1 sequence type, within the promoter region. These genes are involved in biological processes critical to flowering. Further refinement of candidate genes was achieved through Weighted Gene Co-expression Network Analysis (WGCNA), which identified the co-expressed genes of PmMYB21 during flowering activity. Integrating Dap-seq and WGCNA data, we narrowed down the candidate gene list to 54, with a focus on 4 MADS-box genes and 2 hormone signaling genes that are crucial to the flowering process under low-temperature conditions. This study offers valuable insights into the molecular underpinnings of PmMYB21’s role in the low-temperature flowering regulation of mei, paving the way for the development of new cultivars adapted to early blooming.