Seed coat-derived ABA regulates seed dormancy of Pyrus betulaefolia by modulating ABA and GA balance

Xiaoting Wang¹Lufang He²Jianzhao Li³Songling Bai⁴Yuanwen Teng^4*Wei Hui^2*

• ¹Xi’an Botanical Garden of Shaanxi Province (Institute of Botany of Shaanxi Province), Xi'an, China
• ²Shaanxi Normal University, Xi'an, China
• ³Ludong University, Yantai, China
• ⁴Zhejiang University, Hangzhou, China

Plant seeds have evolved diverse dormancy types and regulatory mechanisms to adapt to environmental conditions and seasonal changes. As a commonly used rootstock for cultivated pears, Pyrus betulaefolia faces challenges in seedling production and large-scale cultivation due to limited understanding of seed dormancy mechanisms. In this study, we report that Pyrus betulaefolia seeds exhibit non-deep physiological dormancy, with seed coats playing a pivotal regulatory role.Exogenous abscisic acid (ABA) treatment, fluridone application and seed coat bedding assay demonstrated that dormant seed coats actively synthesized ABA to inhibit embryo germination during imbibition. ABA in imbibed dormant seed coats stimulated ABA biosynthesis in embryos, leading to increased expression of genes involved in ABA biosynthesis (PbeNCED-3) and ABAresponsive (PbeABI3-1, PbeABI5-1, and PbeABI5-5). Importantly, PbeABI5-5 directly binds to the promoters of GIBBERELLIN 2-OXIDASE 3/4 (PbeGA2ox-3/4) to activate their transcription. We establish that in dormant Pyrus betulaefolia seeds, the seed coat controls embryo dormancy release through coordinated regulation of PbeABI5-GA2ox module, thereby maintaining the critical balance between ABA and GA.