Cloning, Characterization, and Functional Analysis of LeMYB1 and Its Promoter in Lithospermum erythrorhizon

MYB transcription factors (TFs) are well known to play important roles in regulating the biosynthesis of secondary metabolites in plants. Here, LeMYB1, a member of MYB gene family of Lithospermum erythrorhizon was cloned by using rapid amplification of cDNA ends method. Alignment of the predicted translations of LeMYB1 with other MYB proteins revealed that LeMYB1 contains an N-terminal R2R3 repeat and a high degree of amino acid identity to NtMYBJS1 that was involved in jasmonic acid signaling and regulating phenylpropanoid biosynthetic pathway. To reveal the expression pattern of LeMYB1, we cloned its promoter and sequence analysis showed that a number of potential regulatory motifs related to tissue-specific gene expression, abiotic- and biotic-stress responses were predicted. Real-time PCR results suggested that LeMYB1 was dramatically induced transiently during the early stage when L. erythrorhizon cells were transferred from B5 to M9 medium for shikonin formation. Exogenous methyl jasmonate (MeJA), an effective inducer of shikonin biosynthesis, remarkably induced the LeMYB1 expression rapidly. Compared with the treatment of MeJA, IBU, one inhibitor of jasmonate biosynthesis, significantly inhibited LeMYB1 expression. Similarly, 2, 4-D, the other inhibitor of shikonin formation, also markedly repressed the expression of LeMYB1. Tissue-specific expression analysis showed that LeMYB1 mRNA predominantly accumulated in the roots where shikonin was biosynthesized. These results indicated that LeMYB1 gene could be a valuable member of the R2R3-MYB family in L. erythrorhizon and may be involved in the regulation of shikonin biosynthesis.