# Dynamic Metabolome and Transcriptome Profiling Provide Molecular Insights into Floral Bud Differentiation in Michelia ‘Xin’

## TL;DR

This study explores the molecular mechanisms behind flower development in Michelia 'Xin', identifying key genes and pathways involved in the process.

## Contribution

The study provides new insights into the stage-specific regulation of floral bud differentiation in Michelia 'Xin' through integrated transcriptomic and metabolomic profiling.

## Key findings

- Floral bud differentiation in Michelia 'Xin' is divided into five distinct developmental stages.
- Phytohormones and transcription factors synergistically regulate the differentiation process.
- Candidate genes and molecular pathways essential for reproductive organ formation were identified.

## Abstract

Floral bud differentiation (FBD) is a highly organized and regulated process crucial for the development of functional floral organs and plant reproduction. Despite the promising high ornamental value of Michelia ‘Xin’, scarce studies have been conducted on this species, limiting the understanding of its molecular functioning and improvement. This study aimed to characterize the phenology and molecular mechanisms underlying FBD in Michelia ‘Xin’. We characterized the FBD process into five stages (T1 to T5). FBD in Michelia ‘Xin’ is stage-specifically regulated by synergy and interplay between phytohormones and transcription factors. The control of dormancy-related, flowering-promoting and circadian-related genes were essential for the induction and formation of reproductive organs. Key involved molecular pathways and candidate genes were screened out. Our findings offer important resources for dissecting the molecular network regulating FBD and improving the ornamental value of Michelia ‘Xin’.

Michelia ‘Xin’ is an evergreen rare ornamental tree species that undergoes FBD only once but blooms twice a year. However, the molecular mechanisms controlling its FBD process remain largely unknown. This study characterized the FBD process and delved into the key molecular regulatory mechanisms through transcriptomic and metabolomic analyses of developing flower buds. FBD in Michelia ‘Xin’ was characterized into five stages, including vegetative (T1), floral meristem transition (T2), tepal primordia differentiation (T3), stamen primordia differentiation (T4), and pistil primordia differentiation (T5). Analyses revealed a stage-specific metabolic and transcriptional regulation of FBD, with increasing numbers of differential metabolites and a decreasing number of DEGs from T1 to T5. Most phytohormone and transcription factor-related DEGs were highly induced from T2. The down-regulation of dormancy-associated protein homologs and CONSTANS-LIKE proteins associated with significant induction of flowering-promoting factor, CLAVATA3, trichome birefringence-like, and GRAVITROPIC IN THE LIGHT proteins was essential for the induction and reproductive organs’ development. Porphyrin biosynthesis, chlorophyll a-b binding proteins, DNA replication, flavonoid biosynthesis, and starch and sucrose metabolism were also significantly induced from T2. Key pivotal candidate genes were screened out. Our results provide fundamental resources for dissecting the molecular network regulating FBD and molecular-assisted flowering control in Michelia ‘Xin’.