International Journal of Horticulture, 2024, Vol.14, No.6, 438-450 http://hortherbpublisher.com/index.php/ijh 440 genes. MeGI is an autosomal gene that encodes homeodomain transcription factors that regulate flower development and anther fertility in a dose-dependent manner (Akagi et al., 2014). Figure 1 Functional analysis of OGI andMeGI (Adopted from Akagi et al., 2014) 2.2 Environmental factors influencing sex determination Climate change drivers can influence sex determination in some intersex plants. For example, biomass accumulation, photosynthetic capacity and water and nitrogen utilization rates of female aspen trees increase significantly under high temperature conditions, while the positive effects of high CO2 concentration on male aspen trees are higher than that of female aspen trees, which may affect the distribution and population dynamics of dioecious plants in the future (Chen et al., 2020). It is known that environmental factors, including temperature and CO2, can affect the expression of sex-determining genes in other plant species. This suggests that similar mechanisms might be at play in E. ulmoides and other dioecious plants. Nutritional and hormonal factors also play a role in sex determination. Plant hormones, such as cytokinins, have been implicated in the regulation of sex expression in several dioecious species (Leite Montalvão et al., 2021). Regulation of gibberellin can lead to high differentiation of male flowers in pomegranate during growth (Engin and Gökbayrak, 2019). In Eucommia ulmoides, the presence of phytohormone-response cis-elements in MADS-box genes suggests that hormonal regulation could be a critical factor in sex determination (Zhang et al., 2023). Additionally, nutritional status can influence the development and differentiation of male and female flowers, although specific studies on E. ulmoides are needed to confirm this (Heikrujam et al., 2014). 2.3 Epigenetic regulation in sex determination Epigenetic mechanisms, such as DNA methylationexhibit 5' cytosine methylation and inhibition of MeGI expression in the bud that forms the male flower, but not in the rest of the plant body or in the bud that forms the female flower, and when treated with methylation inhibitors the developing male flower causes its sex reversal to
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