Cloning and expression analysis of LoCCD8 during IAA-induced bulbils outgrowth in lily (Oriental Hybrid ‘Sorbonne’)

Abstract Aerial bulbils, which resemble tiny bulbs, develop from axillary buds and facilitate rapid propagation of Lilium . In most species of lily, bulbils are perpetually dormant and little is known about induction of these vegetative structures. Herein, we proposed that strigolactones (SLs) may regulate the induction of bulbils in Lilium . We tested this hypothesis by isolating and investigating the expression patterns of 2 copies of the carotenoid cleavage dioxygenase8 ( CCD8 ) gene in lily— LoCCD8a and LoCCD8b —with regard to biosynthesis of SLs. Expression analyses revealed that LoCCD8a principally is expressed during vegetative growth, whereas LoCCD8b mainly is expressed during reproductive growth. The maximum quantity of LoCCD8a transcripts was observed in the basal plate in most developmental stages, which suggests that SLs may originate from underground parts, especially the basal plate, and move upward. The effects of treatments with indole-3-acetic acid or SL analog (GR24) on outgrowth of bulbils and expression of LoCCD8 genes suggested that SLs function downstream of auxin to inhibit the outgrowth of bulbil. The expression patterns of LoCCD8a and LoCCD8b at sprouting and bulblet weighting stages also implied that SLs may function in nutrient redistribution. Our findings are expected to promote the utilization of bulbils as vegetative propagules for commercial practice.