International Journal of Horticulture, 2024, Vol.14, No.6, 438-450 http://hortherbpublisher.com/index.php/ijh 438 Research Insight Open Access Sex Determination Pathways in Dioecious Plants: Insights from Eucommia ulmoides Huaijuan Jiao1, Xi Chen2 , Degang Zhao1,2 1 National-local Joint Engineering Research Center of Karst Region Plant Resources Utilization & Breeding (Guizhou), College of Life Sciences/Institute of Agro-Bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China 2 Plant Conservation & Breeding Technology Center, Guizhou Key Laboratory of Agricultural Biotechnology/Guizhou Institute of Prataculture, Guizhou Academy of Agricultural Sciences, Guiyang, 550006, Guizhou, China Corresponding authors: 15761626900@163.com; dgzhao@gzu.edu.cn International Journal of Horticulture, 2024, Vol.14, No.6 doi: 10.5376/ijh.2024.14.0043 Received: 13 Nov., 2024 Accepted: 17 Dec., 2024 Published: 30 Dec., 2024 Copyright © 2024 Jiao et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Jiao H.J., Chen X., and Zhao D.G., 2024, Sex determination pathways in dioecious plants: insights from Eucommia ulmoides, International Journal of Horticulture, 14(6): 438-450 (doi: 10.5376/ijh.2024.14.0043) Abstract Eucommia ulmoides, a dioecious plant endemic to China, holds significant medicinal and economic value. This study, utilizing high-quality chromosome-level genome sequences and transcriptome data, reveals the mechanisms of sex determination in E. ulmoides. Key genes associated with sex differentiation, such as EuAP3 and EuAG within the MADS-box transcription factor family, were identified. The results demonstrate that these genes exhibit significant sex-biased expression in male and female individuals, highlighting their crucial roles in sex determination. Additionally, several sex-linked molecular markers were discovered, which can be used for early sex identification, thereby optimizing breeding strategies. The study not only provides new insights into the mechanisms of sex determination in E. ulmoides but also offers theoretical support for the improvement of other economically important dioecious crops. The findings are of great significance for enhancing the breeding efficiency of E. ulmoides and other dioecious plants. Keywords Eucommia ulmoides; Sex determination; Dioecious plants; Genome assembly; Transcriptome analysis; MADS-box genes; Sex-biased genes; Breeding 1 Introduction Dioecious plants, which have distinct male and female individuals, represent a fascinating minority within the plant kingdom, accounting for approximately 5%-10% of flowering plant species (Kersten et al., 2017; Leite Montalvão et al., 2021; Razumova et al., 2023). This separation of sexes provides a unique opportunity to study the mechanisms of sex determination and the evolution of sex chromosomes. Unlike hermaphroditic plants, which possess both male and female reproductive organs within the same flower, dioecious plants must rely on genetic and environmental cues to determine sex, making them an excellent model for understanding the complexities of sex expression and differentiation (Heikrujam et al., 2014; Pannell, 2017; Leite Montalvão et al., 2021). Understanding the mechanisms of sex determination in dioecious plants is crucial for several reasons. Firstly, it provides insights into the evolutionary processes that lead to the development of separate sexes from hermaphroditic ancestors (Wang et al., 1999; Pannell, 2017; Henry et al., 2018; Leite Montalvão et al., 2021). Secondly, it aids in the identification of sex-determining regions (SDRs) and sex chromosomes, which are essential for breeding programs and the cultivation of economically important dioecious crops (HIrish and Nelson, 1989; Heikrujam et al., 2014; Razumova et al., 2023). Advances in genome sequencing and gene editing have facilitated the discovery of sex-determining genes and pathways, revealing that similar genetic mechanisms may be employed across different species to achieve dioecy (Wang and Zhang, 2017; Leite Montalvão et al., 2021; Zhang et al., 2022). Eucommia ulmoides, commonly known as the hardy rubber tree, is a dioecious plant endemic to China with significant medicinal and economic value (Du et al., 2023; Zhang et al., 2023). It is renowned for its production of α-linolenic acid and gutta, a natural rubber-like substance, making it a valuable resource for both pharmaceutical
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