GENETIC DIFFERENCES BETWEEN DENDROBIUM CHRYSOTOXUM NATIVE TO NORTHEASTERN AND NORTHERN REGIONS OF THAILAND BASED ON GALANTHUS NIVALIS AGGLUTININ-RELATED LECTINS AND INTERNAL TRANSCRIBED SPACER REGIONS OF RIBOSOMAL DNA

Abstract

Dendrobium chrysotoxum Lindl., native to the Northeastern region and that native to the Northern region of Thailand have some different morphological characters. Their genetic differences were then determined at molecular level. Galanthus nivalis agglutinin (GNA)-related lectins were purified from the pseudobulbs using mannan-agarose column chromatography. The molecular masses of polypeptide subunit and native form, and pI of GNA-related lectin were 13.9 kDa, 54.1 kDa, and 5.16 for D. chrysotoxum (Northeast) while they were 13.7 kDa, 48.2 kDa, and 4.90 for D. chrysotoxum (North), respectively. The sequence tags from liquid chromatography-tandem mass spectrometry (LC-MS/MS) of both lectins were identical to parts of a lectin precursor from D. findleyanum. The lectins exhibited divergent abilities to agglutinate erythrocytes and were named D. chrysotoxum agglutinin-Northeast (DCA-NE), and D. chrysotoxum agglutininNorth (DCA-N). For binding activities, the activities of DCA-NE and DCA-N decreased after treatment with 2- mercaptoethanol; they also showed different specificities towards D-mannose. The lectins showed variation at nucleotide and deduced amino acid sequences. From internal transcribed spacer (ITS) sequences, the genetic distance between the two orchids had greater value than those among many Dendrobium species. The molecular data revealed that D. chrysotoxum native to the different geographical regions of Thailand had a large genetic difference; and should be placed to be as two species or at least two varieties of the genus.