Genome-wide transcriptome profiling provides insights into floral bud development of summer-flowering Camellia azalea

Zhengqi Fan,Bin Wu,Zhongchi Liu,Xinlei Li,Hengfu Yin,Jiangying Wang,Jiyuan Li

doi:10.1038/srep09729

Abstract

The transition from vegetative to reproductive growth in woody perennials involves pathways controlling flowering timing, bud dormancy and outgrowth in responses to seasonal cues. However little is known about the mechanism governing the adaptation of signaling pathways to environmental conditions in trees. Camellia azalea is a rare species in this genus flowering during summer, which provides a unique resource for floral timing breeding. Here we reported a comprehensive transcriptomics study to capture the global gene profiles during floral bud development in C. azalea. We examined the genome-wide gene expression between three developmental stages including floral bud initiation, floral organ differentiation and bud outgrowth, and identified nine co-expression clusters with distinctive patterns. Further, we identified the differential expressed genes (DEGs) during development and characterized the functional properties of DEGs by Gene Ontology analysis. We showed that transition from floral bud initiation to floral organ differentiation required changes of genes in flowering timing regulation, while transition to floral bud outgrowth was regulated by various pathways such as cold and light signaling, phytohormone pathways and plant metabolisms. Further analyses of dormancy associated MADS-box genes revealed that SVP- and AGL24- like genes displayed distinct expression patterns suggesting divergent roles during floral bud development.

Highlights

The transition from vegetative to reproductive growth in woody perennials involves pathways controlling flowering timing, bud dormancy and outgrowth in responses to seasonal cues
We showed that transition from floral bud initiation to floral organ differentiation required changes of genes in flowering timing regulation, while transition to floral bud outgrowth was regulated by various pathways such as cold and light signaling, phytohormone pathways and plant metabolisms
We showed the development of floral buds and floral organs was associated with bud size (Fig. 1), and we identified three representative stages of floral bud development, including floral bud initiation, floral organ differentiation, and floral bud outgrowth stages (Fig. 1)

Summary

Introduction

The transition from vegetative to reproductive growth in woody perennials involves pathways controlling flowering timing, bud dormancy and outgrowth in responses to seasonal cues. There is a great diversity of plant adaptations to seasonal cues, the model systems have provided foundations to uncover the molecular mechanisms of annuals as well as perennials Some key integrators, such as CONSTANS (CO) and FLOWERING LOCUS T (FT), have been shown to possess conserved functions in the control of flowering time in both annuals and perennials[9]. Characterization of the evergrowing (evg) mutant has revealed multiple MADS-box genes [Dormancy-associated MADS-box (DAM)] which were required for growth cessation[12] These DAM genes were found to be members of SVP/AGL24 sub-clade of MADS-box gene family which has been shown to be involved in flowering time control in A. thaliana[13]. Other systems biology investigations, such as gene co-expression network, Gene Ontology (GO) analysis and gene family analysis, have greatly improved our knowledge of gene functions by interrogating high-throughput transcriptome data

Methods

Results

Conclusion