Abstract
Flowering is crucial to plant reproduction and controlled by multiple factors. However, the mechanisms underlying the regulation of flowering in perennial plants are still largely unknown. Here, we first report a super long blooming 1 (slb1) mutant of the relict tree Liriodendron chinense possessing a prolonged blooming period of more than 5 months, in contrast to the 1 month blooming period in the wild type (WT). Phenotypic characterization showed that earlier maturation of lateral shoots was caused by accelerated axillary bud fate, leading to the phenotype of continuous flowering in slb1 mutants. The transcriptional activity of genes related to hormone signaling (auxin, cytokinin, and strigolactone), nutrient availability, and oxidative stress relief further indicated active outgrowth of lateral buds in slb1 mutants. Interestingly, we discovered a unique FT splicing variant with intron retention specific to slb1 mutants, representing a potential causal mutation in the slb1 mutants. Surprisingly, most slb1 inbred offspring flowered precociously with shorter juvenility (~4 months) than that (usually 8–10 years) required in WT plants, indicating heritable variation underlying continuous flowering in slb1 mutants. This study reports an example of a perennial tree mutant that flowers continuously, providing a rare resource for both breeding and genetic research.
Highlights
Flowering, a phase change from vegetative to reproductive growth, is the most dramatic phase change and critical developmental switch in a plant’s life cycle
We found that multiple transcription factor (TF) families, including FAR1, bHLH, MIKC_MADS, MYB, bZIP, HD-ZIP, AUXIN RESPONSE FACTORs (ARFs), C2H2, C3H, and SBP, were differentially expressed in slb[1] mutants compared to wild type (WT) plants at all developmental stages (Supplementary Fig. 2), indicating that developmental heterogeneity is at least partially caused by differential transcriptional regulation mediated by distinct combinations of TFs
Indeterminate shoot growth in slb[1] mutants of L. chinense Plants have evolved species-specific visual appearances and structural features to enable them to optimize their adaptation to the environment and reproductive strategies
Summary
A phase change from vegetative to reproductive growth, is the most dramatic phase change and critical developmental switch in a plant’s life cycle. As sessile organisms living in constantly changing environments, have evolved sophisticated mechanisms to sense changing environments and adjust development to ensure the optimal timing of flowering, thereby maximizing their reproductive success and ensuring the continuation of their species[1]. Decades of research in model plant systems have provided most of what we currently know about the regulatory mechanism of flowering timing. Multiple major genetic pathways have been proposed to integrate both external cues (photoperiod, cold, and ambient temperature) and endogenous cues (gibberellin, age, and carbohydrate state) to determine the timing of flower initiation[3,4,5]. Recent advances have integrated epigenetic regulation factors (chromatin remodeling, histone modification, and miRNAs) into known flowering pathways, which synergistically contribute to
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