# The Snapdragon LATE Elongated Hypocotyl
## 4 Discussion  
In this work, we have performed a functional analysis of the _Antirrhinum majus LHY_ gene. The _LHY_ gene is found as a single copy gene in many plants such as _Petunia_, Arabidopsis, tomato, or _Nicotiana attenuata_[23; 57]. Our results indicate that in _Antirrhinum_ there is a single gene that may have similar functions to the ones described in Arabidopsis, _Petunia_, or _Nicotiana_, including control of growth and scent emission. In this work, we have uncovered a function in floral development where it enhances growth speed. We found that loss of function of _LHY_ in _Antirrhinum_ does not affect organ identity. Despite the importance of the plant circadian clock on the maintenance of the photosynthetic apparatus [63; 64], our results indicate that the plant circadian clock is not involved in the degradation of the chlorophyll machinery during petal development. Sepaloid petals result from decreased activity of B function genes and their targets [65], but we could not find evidence for an effect of _AmLHY_ on petal identity. The transcriptional structure of the plant circadian clock varies between tissues and possible changes of the plant clock in petals versus other tissues or organs remains to be determined. The size of plant lateral organs is the result of a combination of cell division and expansion. A variety of mutants affecting these processes in _Antirrhinum_ show that petal growth can be differentially affected by genes indicating an intricate coordination of cell division, cell expansion, and compensation mechanisms [66]. The plant circadian clock is known to control cell expansion, our results demonstrate that _AmLHY_ did not affect equally all the floral parameters analyzed. Our results did not differ from the findings in nightshades as down regulation of _LHY_ does not affect floral size, petal junction distance, and corolla length, in _Nicotiana attenuata_ or _Petunia_[27; 28]. The temporal timing of cell division and expansion plays a key role in plant development. Both the length of the growth period and growth rate determine the final size of an organ. Our phenolic analysis of the _Antirrhinum_ flower shows that the growth period is not controlled by _AmLHY_ whereas the growth rate is substantially reduced. We may conclude that the period between cell divisions could be elongated in _RNAi:AmLHY_ plants, resulting in organs with fewer and/or smaller cells. This hypothesis may require additional testing. Recent studies indicate that _LHY_ represses abscisic acid (ABA) synthesis and signaling pathways [61], indicating that the newly identified effect of _AmLHY_ on growth may occur via modulation of ABA. Our results are congruent due to the slow growth rate observed in RNAi plants highlighting the role of the circadian clock in flower development. The fact that floral organ size is not significantly reduced but growth speed is slowed in _AmLHY_ knockdown lines indicates that compensation in terms of growth time may be occurring in order to achieve wild type organ size. Floral scent profiles play a key role in the interaction of plants with both pollinators and pests [14]. The volatile blend is thought to be a complex interphase of interaction, and it is specific for a species [60]. The _A. majus_ scent profile is highly complex as it comprises phenylpropanoids/benzenoids, and terpen amongst the major VOCs. Previous studies showed that silencing _ZTL_ in _Nicotiana attenuatta_ causes a major reduction of benzyl acetone while _LHY_ causes an early emission. The down regulation of _PhLHY_ causes an earlier emission and reduction of methyl benzoate and benzyl benzoate [27; 28]. Interestingly, bumblebees, one of the _A. majus_ pollinators, are capable of detecting variations in aroma blends among snap dragon species, and wild _Antirrhinum_ emitting different scent blends appear to have specialized pollinators [67; 68]. As silencing _AmLHY_ resulted in new aroma ratios, it may alter pollininators behaviour.