Abstract: 【Objective】 In this study, the responses of miR828 and its targets to phosphate deficiency and the role of miR828 in anthocyanin biosynthesis under phosphate deficiency were investigated by using wild-type and miR828 overexpressed transgenic tomatoes. 【Method】 The potential targets of miR828 were predicted and validated by psRNATarget and RLM-5′RACE, respectively. An alignment of deduced amino acid sequences of SlMYB7-like with orthologs from Arabidopsis thaliana (AtMYB7) and Antirrhinum majus (AmMYB330) was constructed using MegAlign of DNAStar. The phylogenetic tree of SlMYB7-like and the selected R2R3 MYBs was constructed using neighbor-joining method using MEGA5. The expressions of miR828 and SlMyb7-like in AC, MicroTom and LA1996 tomato seedlings were analyzed. The expression of miR828 in different tissues/organs of tomato (AC) was analyzed by qRT-PCR. Wild-type and miR828 overexpressed transgenic tomatoes were cultured under normal phosphate (KH₂PO₄ 3.4 g·L^-1) and phosphate deficiency (KCl 1.86 g·L^-1) for 15 d. The phenotypic changes and the expression of miR828, SlMyb7-like (SGN-U320618), several anthocyanin biosynthetic genes as well as the anthocyanin content were detected. 【Result】SlMyb7-like was validated to be a direct target of miR828. Protein sequence analysis showed that the SlMYB7-like protein shares the highest homology with the Arabidopsis subgroup 4 MYB7 (AtMYB7), and Snapdragon MYB330, having more than 80% sequence similarity. Phylogenetic analysis grouped SlMYB7-like in a clade with AtMYB7 and AmMYB330. SlMYB7-like contains the conserved amino acid motif ([D/E]L_X2[R/K]_X3L_X6L _X3R/DLIVRLHSLLGNRWSLIAGR), a signature feature common to subgroup 6 R2R3 MYBs (AtMYB75/90/113) that are involved in anthocyanin biosynthesis. The highest abundance of miR828 was detected in MicroTom seedlings, where the transcript of its target gene (SlMyb7-like) was accumulated the lowest. The expression of miR828 in different tissues of tomato tested was very low with relatively higher levels in buds, flowers and green fruits. Under the normal phosphate condition, the expression of anthocyanin biosynthetic genes in the miR828 over-expressed tomatoes decreased by 30%-60% and the content of anthocyanin decreased by 40%. Phosphate deficiency induced both the expression of miR828 and SlMyb7-like. The expression of SlMyb7-like, anthocyanin biosynthetic genes and the content of anthocyanin in the miR828 overexpressed tomatoes were lower than that in control plants under phosphate deficiency. The above data suggest that miR828 negatively regulates the anthocyanin biosynthesis in tomato under phosphate deficiency.【Conclusion】SlMyb7-like is a direct target gene of miR828. Both the expressions of miR828 and SlMyb7-like are induced under phosphate deficiency. MiR828 negatively controls anthocyanin pathway by repressing the expression of SlMyb7-like, and thereby negatively regulating anthocyanin biosynthetic genes in tomato under phosphate deficiency.

Key words: tomato, phosphate deficiency, miR828, SlMyb7-like, anthocyanin