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

as visualised in double flowers.
Chapter 6
Many studies on the genetics of flower development have been carried out in
Arabidopsis and other model species creating an extensive catalogue of homeotic
mutants, showing wide allelic series of floral homeotic genes in many cases.
Strikingly, we found a novel homeotic mutant phenotype in lily flower that has
not been reported in other species. The phenotype, with normal tepals in the first two
whorls, presents a complete homeotic conversion of its stamens into tepals, as it is seen
in the agamous-like mutant, but shows a completely normal carpel development in its
innermost whorl, differing from the C-type loss of function. We called this phenotype
festiva (from the Latin, "joyful, pretty") (Figure 1 and 2).
This phenotype is interesting commercially not only for having more tepals, but
also for not producing pollen, since in mature stages of wild-type flowers it speckles
tepals, clothes and the furniture. Many consumers remove the lily anthers prior to
display, in order to avoid pollen flecking. Phenotypes such as festiva are, therefore, of
great interest to breeding programs, and unravelling the molecular mechanisms behind
this phenotype may lead to the development of molecular tools that facilitate replacing
stamens by tepals.
Unfortunately, we were not able to perform molecular analysis of the festiva
genotype in the time frame established to generate this thesis, but instead, we tried here
to draw some hypotheses that can be explored later, raising some fascinating
perspectives for further investigation.
Hypotheses regarding the festiva phenotype
The phenotype shown by festiva can, with its perfect homeotic changes of
stamens into tepals, be easily pictured as an extension of an A-type function towards
the third whorl, to the detriment of the C-type function in this whorl.
The challenge, however, is in understanding the exact mechanism through
which this function replacement originated. We speculate that the whorl-specific
homeotic change seen in festiva can be due to modifications of regulatory elements of
A or C genes or to a third whorl-specific factor acting in stamen development.
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