DMMADS4, A DEF-LIKE GENE FROM DENDROBIUM IS REQUIRED FOR FLORAL ORGAN IDENTITY AND FLOWER LONGEVITY OF ORCHID

Two Class B MADS-Box genes were isolated from Dendrobium moniliforme i.e. DMMADS4 and DMPI. DMMADS4 encodes for protein with a predicted length of 224 amino acids; it shares 89% identity with PeMADS4 at the amino acid level. DMPI encodes for a 210 amino acid protein that showed 94% identity to PeMADS6 from Phalaenopsis. The results from RT-PCR analysis showed that DMMADS4 was transcribed in petals, lip and column; however, DMPI was expressed in all four floral whorls.
Expression pattern of DMMADS4 is broader than that of PeMADS4 which is expressed only in the part of the lip.
Therefore, DMMADS4 does not specify only lip development like PeMADS4. Interestingly, the expression of DMMADS4 and DMPI were also detected during the ovule development.
A high level of expression of both genes was found in pre-pollinated ovules of flowers.
Yeast two-hybrid analysis demonstrated that DMMADS4 and DMPI were able to form heterodimers.
The phenotype of 35S::DMMADS4 transformed Arabidopsis plants was indistinguishable from that of wild-type plants except plants size was reduced.
However, in the 35S::DMPI plants, flowers have conversed sepals into a petaloid-like structure in whorl 1. The crossing between 35S::DMMADS4 and 35S::DMPI resulted in the alteration of sepals into petaloid-like structures in whorl 1. Also, the plants maintained flower bud stage longer than wild-type plants.
These results suggested that the B-function genes, DMMADS4 and DMPI, are necessary for petal development and might be necessary for flower longevity of orchid.

XXIII International Eucarpia Symposium, Section Ornamentals: Colourful Breeding and Genetics

S. Sirisawat, N. Fukuda, H. Ezura, T. Handa

MADS-Box genes, Dendrobium moniliforme, petaloid, heterodimer, flower longevity

https://doi.org/10.17660/ActaHortic.2009.836.37