Cloning And Characterization Of B Function MADS-box Genes Involved In Floral Development From Phalaenopsis Orchid

Genes of the MADS box family encoding transcription factors are found in a diverse range of eukaryotic organisms including yeasts,plants,insects,amphibians and mammals.MADS-box gene family plays a key role in the plant development, especially the specification of the identity of the floral organs.However,little is known in the monocot species compared with the dicot.The highly evolved flower of orchid with colorful sepals and fused column offers an opportunity to discover novel MADS-box genes involved in the floral development in monocot species.We have cloned and characterized three homologous PISTALLATA-like(PI-like)genes and a APETALA3-like(P3-like)gene from Phalaenopsis hybrid cultivar named phPI9(Phalaenopsis PI STILLATA#9), PhPI10,PhPI15 and PhAP3(Phalaenopsis APETALA3),respectively.The deduced amino acid residue sequences of PhPI9,PhPI10 and PhPI15 all have the typical PI-motif.They also formed a subclade with other monocot PI-type genes in the phylogenetic analysis;the deduced amino acid residue sequence of PhAP3 has a conserved PI-derived motif and a paleo-AP3 motif.It falls into the monocot AP3-type in the phylogenetic tree.Southern analysis showed that all these four genes were present in the Phalaenopsis orchid genome as a single copy.Furthermore.PhPI15 was expressed in all the whorls of the Phalaenopsis flower,while PhPI9 and PhPI10 were only expressed in the lip of the Phalaenopsis flower.All these three PI-like genes were not expressed in vegetative organs.But the expression of PhAP3 can be detected in all vegetative organs and all floral organs.The expressions of PI-like genes of Phalaenopsis were focused in the pollen while the expression signal of PhAP3 was found enrichment in the anther cap.The flowers of the transgenic tobacco plants ectopically expressing PhPI15 showed reduced size compared with the wild type plant and male-sterile phenotypes.Concerning all mentioned above,we have cloned four B-function MADS-box genes involved in the floral organ identity in Phalaenopsis orchids.