Flower development of Lilium longiflorum - The Lilium information ...

Epilogue
is an appropriate system allowing (or speeding up) heterologous functional
characterisation of floral genes.
Transformation system for lily
In our efforts to genetically transform lily, described in chapter five, we were
able to generate three transgenic lily clones that were resistant to bialaphos in in vitro
conditions via particle bombardment.
This transformation method has proven to be of low efficiency in lily and the
current trend is towards Agrobacterium systems (Mercuri et al., 2003). However, our
preliminary results indicated that this system is also recalcitrant and considerable input
is still needed to increase its applicability in lily species.
The low number of transgenic clones recovered in the work reported in this
chapter did not allow us to reach further goals, such as characterising the activity of a
transcription factor and of a gene promoter from dicot species in lily. Nevertheless,
given the recalcitrance of lily to transformation, obtaining three transgenic clones out
of a single experiment is already a remarkable result.
We conclude, based on this work and on our further experience, that lily
transformation is feasible, although the particle bombardment protocols currently
available do not always provide us with reproducible transformation rates.
Nevertheless, we suggest more investigation into methods based on Agrobacterium,
since a consistent transformation method is already available for other Liliaceae
species, such as onion and shallots (Zheng et al., 2001).
Novel floral mutants of lily and new challenges
Two types of homeotic floral mutants were found in lily during our studies.
Some double flowers, i.e. agamous-like homeotic lily mutants, are commercially
available and the correlated phenotype is found in several species. It is clear that it
involves the C function of the ABCDE model (Roeder and Yanofsky, 2001), due to its
coupled abnormalities (homeotic mutation and loss of floral determinacy). It would be
very interesting to investigate at what level this function is misregulated. It is possible
that the LLAG1 gene is involved in the process, since it showed a C function when
expressed in Arabidopsis (chapter two).
We also speculated about a novel homeotic floral phenotype found in lily and
never observed in other species, which challenges the current ABCDE model because
it presents a homeotic change in only one whorl. In this conceptual chapter, we raised
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