To study the mechanism of pomegranate seed hardness,and the function of transcription factor gene PgMYB in lignin biosynthesis pathway of pomegranate seed coat,we measured the seed hardness and total lignin content in different pomegranate cultivars.A novel MYB transcription factor gene PgMYB was isolated from cultivar ‘Hongyushizi’ by reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE).The expression levels of PgMYB were analyzed by real time-PCR.The results showed that:(1)The hardness of pomegranate seed and the total lignin content in seed coat were positively correlated with a correlation coefficient of 0.906.(2)The full-length cDNA of PgMYB was 1 088 bp with an open reading frame of 921 bp encoding a protein of 306 amino acid residues.It’s a typical R2R3-MYB transcription factor gene in plant with two MYB DNA binding domains at its N-terminus.Blast X analysis showed that PgMYB had high identity with Leucaena leucocephala MYB1 and Arabidopsis thaliana MYB4 as 89% and 84%,respectively.(3)Real time-PCR analysis indicated that the relative expression of PgMYB was negatively correlated with the hardness of pomegranate seed and total lignin content in seed coat.(4)At each stage of ‘Hongyushizi’ fruit development,the relative expression of PgMYB was always negatively correlated with the total lignin content in seed coat.It was speculated that PgMYB might repress the biosynthesis of lignin in pomegranate seed coat.The results expected to lay a foundation for study the mechanism of pomegranate seed hardness.