Abstract
BackgroundFloral transition plays an important role in development, and proper time is necessary to improve the value of valuable ornamental trees. The molecular mechanisms of floral transition remain unknown in perennial woody plants. “Bairihua” is a type of C. bungei that can undergo floral transition in the first planting year.ResultsHere, we combined short-read next-generation sequencing (NGS) and single-molecule real-time (SMRT) sequencing to provide a more complete view of transcriptome regulation during floral transition in C. bungei. The circadian rhythm-plant pathway may be the critical pathway during floral transition in early flowering (EF) C. bungei, according to horizontal and vertical analysis in EF and normal flowering (NF) C. bungei. SBP and MIKC-MADS-box were seemingly involved in EF during floral transition. A total of 61 hub genes were associated with floral transition in the MEturquoise model with Weighted Gene Co-expression Network Analysis (WGCNA). The results reveal that ten hub genes had a close connection with the GASA homologue gene (Cbu.gene.18280), and the ten co-expressed genes belong to five flowering-related pathways. Furthermore, our study provides new insights into the complexity and regulation of alternative splicing (AS). The ratio or number of isoforms of some floral transition-related genes is different in different periods or in different sub-genomes.ConclusionsOur results will be a useful reference for the study of floral transition in other perennial woody plants. Further molecular investigations are needed to verify our sequencing data.
Highlights
Floral transition plays an important role in development, and proper time is necessary to improve the value of valuable ornamental trees
The early flowering (EF) buds were subgrouped into three consecutive differentiation stages, namely, vegetative buds (Vb), transition buds (Tb), and reproductive buds (Rb), according to their anatomical structure (Fig. 1b)
Since the molecular regulation of floral transition begins far before morphological changes occur, many critical molecular regulations should have already occurred in the Vb [29, 31, 47]
Summary
Floral transition plays an important role in development, and proper time is necessary to improve the value of valuable ornamental trees. A set of floral transition-related genes, such as SPL (Squamosa-promoter binding protein-like) [5,6,7], TOC (Timing of cab expression 1) [8], LUX (Luxarrhythmo) [8], PIF (Phytochrome interacting factor) [9], CO (constans) [10], FRI (Frigida) [11], GA20ox (GA20oxidases) [7], GA3ox (GA3oxidases) [12], SOC1 (Suppressor of overexpression of constans 1) [13], have been detected, in addition to others [14, 15] These genes are mainly categorized into five major pathways that regulate floral transition, including the age pathway, photoperiod and circadian clock pathway, autonomous pathway, vernalisation pathway and GA pathway [4].
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