Morphological, phenological, and transcriptional analyses provide in sight into the diverse flowering traits of a mutant of the relic woody plant Liriodendron chinense

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(slbl)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 slbl 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 slbl mutants.Interestingly,we discovered a unique FT splicing variant with intron retention specific to slbl mutants,representing a potential causal mutation in the slbl mutants.Surprisingly,most slbl 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 slbl mutants.This study reports an example of a perennial tree mutant that flowers continuously,providing a rare resource for both breeding and genetic research.