Abstract:

In order to explore the role of AmMYB2 in the betalain synthesis in Amaranthus tricolor，the bioinformatics，gene expression and functional analysis of AmMYB2（Genbank accession No. KY814751.1）in the red amaranth cultivar‘Dahong’were conducted. The results showed that the open reading frame（ORF）of the AmMYB2 is 678 bp in length. The coding protein molecular mass fraction is 25.96 kD，which belongs to R2R3 MYB transcription factor with R2R3 MYB domain. Subcellular localization assay revealed that the AmMYB2 protein was localized in the nucleus. Nucleotide sequence analysis revealed that the AmMYB2 is relatively close to betalain synthesis-related BvMYB1 and AmMYB1，with an identity of 62.11% and 49.93%，respectively. Quantitative real-time PCR（qRT-PCR）results showed that the expression level of AmMYB2 was higher in red amaranth cultivar than that in green，and was different in different tissues and the different parts of leaves from the‘Dahong’amaranth，consistent with the proportional to the content of betalains. After the over expression vector of AmMYB2 was constructed and transferred to tobacco and Arabidopsis thaliana，the expression level of AmMYB2 was higher in both plants，without color changes. Therefore，the AmMYB2 may be a positive regulatory factor for the synthesis of betalains in amaranth，and maybe not involved in anthocyanin synthesis.

Key words: Amaranthus tricolor, AmMYB2, betalain, expression analysis, functional identification