Abstract
BackgroundFlower longevity is closely related to pollen dispersal and reproductive success in all plants, as well as the commercial value of ornamental plants. Mutants that display variation in flower longevity are useful tools for understanding the mechanisms underlying this trait. Heavy-ion beam irradiation has great potential to improve flower shapes and colors; however, few studies are available on the mutation of flower senescence in leguminous plants.ResultsA mutant (C416) exhibiting blossom duration eight times longer than that of the wild type (WT) was isolated in Lotus japonicus derived from carbon ion beam irradiation. Genetic assays supported that the delayed flower senescence of C416 was a dominant trait controlled by a single gene, which was located between 4,616,611 Mb and 5,331,876 Mb on chromosome III. By using a sorting strategy of multi-sample parallel genome sequencing, candidate genes were narrowed to the gene CUFF.40834, which exhibited high identity to ethylene receptor 1 in other model plants. A physiological assay demonstrated that C416 was insensitive to ethylene precursor. Furthermore, the dynamic changes of phytohormone regulatory network in petals at different developmental stages was compared by using RNA-seq. In brief, the ethylene, jasmonic acid (JA), and salicylic acid (SA) signaling pathways were negatively regulated in C416, whereas the brassinosteroid (BR) and cytokinin signaling pathways were positively regulated, and auxin exhibited dual effects on flower senescence in Lotus japonicus. The abscisic acid (ABA) signaling pathway is positively regulated in C416.ConclusionSo far, C416 might be the first reported mutant carrying a mutation in an endogenous ethylene-related gene in Lotus japonicus, rather than through the introduction of exogenous genes by transgenic techniques. A schematic of the flower senescence of Lotus japonicus from the perspective of the phytohormone regulatory network was provided based on transcriptome profiling of petals at different developmental stages. This study is informative for elucidating the molecular mechanism of delayed flower senescence in C416, and lays a foundation for candidate flower senescence gene identification in Lotus japonicus. It also provides another perspective for the improvement of flower longevity in legume plants by heavy-ion beam.
Highlights
Flower longevity is closely related to pollen dispersal and reproductive success in all plants, as well as the commercial value of ornamental plants
Ethylene, jasmonic acid (JA), and salicylic acid (SA) signaling pathways were negatively regulated in C416, whereas the BR and cytokinin signaling pathway were positively regulated, and auxin exhibited dual effects on flower senescence in Lotus japonicus
The abscisic acid (ABA) signaling pathway was positively regulated in C416, and ABA might be the major phytohormone factor that promotes senescence when the ethylene signaling pathway is blocked in Lotus japonicus
Summary
Flower longevity is closely related to pollen dispersal and reproductive success in all plants, as well as the commercial value of ornamental plants. Flower longevity is the duration of time that flowers remain open and functional It is an important trait for ornamental plants because of its effects on floral displays. It has been reported that, cysteine protease has the potential to regulate ethylene biosynthesis and signal transduction by acting as a dual-function protein with enzymatic activity and transcriptional factor activity that bonded to the cis element to activate the expression of ACC synthesize gene. Few studies are available on flower senescence of leguminous plants, which cover 20,000 species and play important roles in agronomic activities and environmental improvement due to their nitrogenfixing ability and ornamental value. Stable mutants displaying alterations in flower longevity are ideal tools for understanding the mechanism of flower longevity in Lotus japonicus
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