Temporal and spatial expression patterns of the LEAFY homologue NLF during florogenesis in Narcissus tazetta

Studies of flower development in numerous plants suggest that the LEAFY gene (LFY) of Arabidopsis and its homologues in other species act as integrators of floral inductive signals and determine the fate of meristems. In Narcissus tazetta, the LFY homologue NLF was identified, and its expression pattern during flower development was studied under various temperature conditions. In N. tazetta, flower initiation and differentiation occur within the bulb during summer dormancy, and are promoted by relatively high temperatures (25–30 °C). NLF was detected in the apical meristem throughout its development from the vegetative state to fully differentiated flowers, under ambient summer conditions in Israel. A dramatic increase in expression was observed twice: during meristem transition from vegetative to reproductive development, and during differentiation of flower primordia. At later stages of flower differentiation, NLF was expressed in the developing anthers. NLF was also found in leaf primordia, but not in mature leaves, suggesting a role in young leaf development. Temperature conditions during florogenesis affected NLF expression in the apical meristem. Summer storage of Narcissus bulbs at a constant 30 °C resulted in florogenesis and an expression pattern of NLF similar to that observed under ambient temperatures. However, at 12 °C, meristems remained morphologically vegetative and did not produce flowers. At the same time, a high expression level was observed in these non-differentiated meristems. Our results suggest that NLF plays a major role in floral development of N. tazetta, but that temperature does not affect NLF expression directly.