# Transcriptomic Reprogramming in Leaves During Floral Bud Morphogenesis in Blueberry

## TL;DR

This study explores how blueberry leaves change at the molecular level during flower bud development, revealing key genes and processes involved in this transition.

## Contribution

The study provides novel insights into the transcriptomic reprogramming of blueberry leaves during floral bud morphogenesis and identifies potential regulatory genes.

## Key findings

- Leaf gene expression shifts through four distinct modules associated with photosynthesis, stress, hormone signaling, and carbon metabolism.
- Key flowering genes like FT, AP2, and COL9 show dynamic expression patterns across developmental stages.
- Brassinosteroid signaling is the most represented hormone pathway, with 101 associated genes identified.

## Abstract

Background/Objectives: Floral bud morphogenesis is a critical developmental process determining yield potential in blueberry, yet the molecular regulatory mechanisms in leaves during this phase remain poorly understood. Methods: In this study, we employed a time-series transcriptomic approach to investigate leaf gene expression dynamics during floral bud morphogenesis in rabbiteye blueberry. Leaves were sampled at six time points spanning the critical developmental window from the cessation of summer shoot growth to bud swell and dormancy onset. Results: RNA-seq analysis generated 121.68 Gb of clean data, and weighted gene co-expression network analysis (WGCNA) identified four stage-specific modules (brown, red, blue, turquoise) significantly associated with distinct morphogenetic phases. The brown module (0–6W) was enriched in photosynthesis and hormone signaling pathways, while the red (9W) and blue (12W) modules featured protein processing, stress and hormone signaling, and carbohydrate metabolism. The turquoise module (15W) was dominated by carbon metabolism and flavonoid biosynthesis genes. Key flowering-related genes exhibited dynamic expression patterns: FT was specifically upregulated at the late stage (15W), AP2 genes peaked at mid-stage (9–12W), and COL9 showed early high expression (0–3W). Hormone-related gene analysis revealed extensive involvement of multiple pathways, with brassinosteroid (BR) signaling comprising the largest number of genes (101). Co-expression networks further identified hub genes, including FT, COL9, AP2, ERF1, SR160, LOX3-1, and transcription factor genes like MYB-related, as potential central regulators. Conclusions: Our findings demonstrate that blueberry leaves undergo a phased functional transition from a photosynthetic source to a hub for signal integration and metabolic support during floral bud morphogenesis, actively contributing to reproductive development through systemic signaling. This study provides novel insights into flowering regulation in woody perennials and establishes a foundation for marker-assisted breeding and cropping season management in blueberry.