# Integrated BSA-Seq and WGCNA Analyses Reveal Candidate Genes Associated with Winter Bud Dormancy Maintenance in Fruit Mulberry (Morus spp.)

## TL;DR

This study identifies genes involved in maintaining winter bud dormancy in fruit mulberry, which could help breed varieties with extended ripening periods.

## Contribution

The study integrates BSA-Seq and WGCNA to identify MaSVP as a key gene regulating winter bud dormancy in fruit mulberry.

## Key findings

- MaSVP represses winter bud dormancy release and is crucial for dormancy maintenance.
- Genes like MaSVP, MaSAPK3, and MaCASL2 are downregulated as budburst approaches.
- Winter bud dormancy in Morus wittiorum is linked to ABA and GA metabolism.

## Abstract

The excessively concentrated ripening period of mulberries causes seasonal surplus. Fruit mulberry (Morus spp.) exhibits the unique trait of “simultaneous flowering and leaf flushing”, rendering budburst timing closely correlated with fruit ripening time. Thus, deciphering the molecular mechanism underlying winter bud dormancy maintenance in fruit mulberry is urgently needed. Herein, an F1 hybrid population comprising 337 individuals, derived from Morus wittiorum (♀) and ‘322’ (♂), was utilized as research material. Through Bulked Segregant Analysis Sequencing (BSA-Seq), we successfully mapped a dormancy-associated QTL interval designated as LB (Late Burst), spanning 9,990,001–11,990,000 bp on Chromosome 13. Integrating Weighted Gene Co-expression Network Analysis (WGCNA) results, MaSVP was identified as a candidate gene within this interval. Virus-induced gene silencing (VIGS) of MaSVP in winter buds of Morus wittiorum significantly accelerated budburst compared to the control, demonstrating that MaSVP represses winter bud dormancy release and plays a crucial role in regulating dormancy maintenance in fruit mulberry. Dynamic expression profiling of dormancy-related genes revealed that the transcript levels of MaSVP, MaSAPK3, MaCASL2, and MaPYR8 were significantly downregulated (Tukey’s test, p < 0.05) as budburst approached, whereas those of MaFT and MaGA20ox1-D were significantly upregulated (Tukey’s test, p < 0.05). These results indicate that winter bud dormancy maintenance in Morus wittiorum is associated with abscisic acid (ABA) and gibberellin (GA) metabolism. Collectively, this study provides critical insights into the biological basis of winter bud dormancy maintenance in fruit mulberry and offers valuable genetic resources for breeding late-maturing cultivars.