Silencing Nicotiana attenuata LHY and ZTL alters circadian rhythms in flowers

Abstract

SummaryThe rhythmic opening/closing and volatile emissions of flowers are known to attract pollinators at specific times. That these rhythms are maintained under constant light or dark conditions suggests a circadian clock involvement. Although a forward and reverse genetic approach has led to the identification of core circadian clock components in Arabidopsis thaliana, the involvement of these clock components in floral rhythms has remained untested, probably because of the weak diurnal rhythms in A. thaliana flowers.Here, we addressed the role of these core clock components in the flowers of the wild tobacco Nicotiana attenuata, whose flowers open at night, emit benzyl acetone (BA) scents and move vertically through a 140°arc.We first measured N. attenuata floral rhythms under constant light conditions. The results suggest that the circadian clock controls flower opening, BA emission and pedicel movement, but not flower closing.We generated transgenic N. attenuata lines silenced in the homologous genes of Arabidopsis LATE ELONGATED HYPOCOTYL (LHY) and ZEITLUPE (ZTL), which are known to be core clock components. Silencing NaLHY and NaZTL strongly altered floral rhythms in different ways, indicating that conserved clock components in N. attenuata coordinate these floral rhythms.

Effect of Different Photoperiods on Flower Opening Time in <i>Portulaca umbraticola</i>

“…However, though our results have some degree of similarities with elf3 mutants, the circadian clock is a complex system and variations can be found from species to species, so the reason for the variable period length in LL in P. umbraticola will remains unclear until there is further molecular evidence. Recent studies in Nicotiana attenuata have reported that silencing of clock component genes NaLHY and NaZTL resulted in altered circadian rhythms of flower opening, floral scent emission, and vertical movement of flowers (Yon et al, 2016). This report clearly demonstrated the involvement of the circadian clock components in the rhythmic regulation of physiological processes in floral organs.…”

Fitness consequences of a clock pollinator filter in Nicotiana attenuata flowers in nature

“…Plant growth conditions and phenotyping T 3 homozygous irLHY-406, and irZTL-314 (Yon et al 2016) were used for all pollination experiments described in this study, and the 31 st inbred generation wild-type (WT) Nicotiana attenuata plants were used as pollen donors. In the field, seedlings were transferred into hydrated 50 mm peat pellets and later transplanted to an irrigated field plot at the Lytle Ranch Preserve, as described in Kessler et al 2012.…”

“…For instance, the floral scents of Petunia are under the control of internal clocks, called the circadian clock, and synchronize emissions with the active time of the flower's pollinators (Hoballah et al 2005;Fenske et al 2015). Flower opening/closing and flower movement are also regulated by the circadian clock (Atamian et al 2016;Yon et al 2016). However, it remains largely untested how the circadian clock functions for a plant's reproductive success in nature when more than one pollinator species are available.…”

“…The solanaceous species Nicotiana attenuata, a wild tobacco, is an interesting ecological model plant to study the function of floral rhythms for plant-pollinator interactions. N. attenuata flowers have three distinctive diurnal rhythms; flowers rhythmically open at night and close during the day; emit scents at night; and move vertically (Yon et al 2016).…”

“…Silencing the clock genes alters the plant's floral rhythms and its interaction with the Manduca sexta hawkmoths, under glasshouse conditions (Yon et al 2016). The flowers of N. attenuata LHY (NaLHY)-silenced lines (irLHY) were shifted towards an earlier display and silencing NaZTL (irZTL) abolished floral rhythms (Yon et al 2016;Yon et al 2017; Figure S1). …”