MYB transcription factor genes play important roles in developmental and various other processes in plants. In this
study, functional characterization of AmMYB1, a single-repeat MYB transcription factor isolated from the salt-tolerant
mangrove tree Avicennia marina is reported. AmMYB1 cDNA was 1046 bp in length with an open reading frame of
783 bp, encoding 260 amino acids. The corresponding gene had two introns and three exons and was present as a
single copy in A. marina. The deduced amino acid sequence showed similarities to MYB proteins reported in other
plants, including the conserved MYB binding domain. RNA gel blot analysis showed that the AmMYB1 transcript
expression was more pronounced in green photosynthetic tissue and was strongly induced by stresses such as salt
(500 mM), light (500 μE m−2 s−1), and the exogenous application of ABA (100 μM). An analysis of the upstream sequence
of AmMYB1 gene revealed the presence of regulatory elements identical to those present in the promoters of stress
inducible genes. The promoter was responsive to NaCl and could enhance reporter gene expression in planta. An
in vitro DNA binding assay using the promoter region (TGGTTAG) of the AtRD22 gene and a transactivation assay in
yeast cells suggest the possibility of AmMYB1 protein regulating the expression of other genes during salt stress.
Transgenic tobacco plants constitutively expressing the AmMYB1 transcription factor showed better tolerance to
NaCl stress.