Isolation and characterization of the AGAMOUS homologous gene NTAG in Chinese narcissus (Narcissus tazetta var. chinensis Roem)

Abstract

Amaryllidaceae, a monocot plant family, consists of many important ornamental bulb flower species. Chinese narcissus (Narcissus tazetta var. chinensis Roem), its flowers developed at high temperatures and bloomed at lower temperatures during the Chinese Spring Festival, is a traditional Chinese flower with high economic and ornamental value. To study its flower development, a full length cDNA containing MADS box domain from narcissus was isolated by a reverse transcription polymerase chain reaction (RT-PCR) with degenerate oligo-nucleotide primers derived from a conserved MADS-and K-box domain sequence. The 5′ and the 3′ regions of the gene were amplified using the PCR protocol for the rapid amplification of cDNA ends (RACE). The 690 bp open reading frame encodes 230 amino acid residues. A comparison of the deduced amino acid sequence of NTAG with the sequence of other MADS box proteins showed 91.3% amino acid identities with HAG (Hyacinthus orientalis). Sequence analysis and alignment showed significant similarity with other AG homologues. RNA blot analysis indicated that the narcissus NTAG gene was expressed only in reproductive organs, especially in stamens and carpels. These results indicated that the NTAG gene was an AG homologue and that the AG genes appeared to be structurally and functionally conserved between dicots and monocots.