Genetics, anatomy and expression of antisense ACC oxidase gene in transgenic Dendrobium draconis Rchb.f.

Abstract. This research was aimed to compare chromosome number, anatomy and expression of antisense ACC oxidase gene between nontransgenic and transgenic Dendrobium draconis Rchb.f. obtained by Homkrajae (2005). Plant materials were cultivated on modified MS medium supplemented with 5 mg/L hygromycin and 15% coconut water for four months. It was found that the frequency of hygromycin-resistant D. draconis was 80 % while 20 % were escape plants. One hundred percent of the hygromycin-resistant plants were viable when further cultured on the same medium for eight months. GUS assay used to verify transient gene expression in transgenic D. draconis showed positive results. An anatomical study in leaves, stems and roots of transgenic plants showed positive blue coloration in all tissues while those of nontransgenic plants showed negative results. PCR analysis confirmed the integration of 35S promoter, NOS terminator and antisense ACC oxidase gene in D. draconis. A cytological study revealed that there was no change in chromosome number (2n = 38). Furthermore, both transgenic and nontransgenic orchids exhibited no significant difference in chlorophyll content.