MiR858b Inhibits Proanthocyanidin Accumulation by the Repression of and in Persimmon.

Persimmon proanthocyanidin (PA) biosynthesis is controlled by structural genes and regulated by transcription factors (TFs). MicroRNAs are a key factor involved in regulating gene expression at the posttranscriptional level whose functions in persimmon PA biosynthesis are poorly understood. Here, we identified a microRNA, miR858b, that putatively targets two R2R3-MYB TFs, and . , , and miR858b showed divergent expression patterns during fruit development, and the interaction between miR858b and or was experimentally validated by 5' RNA ligase-mediated RACE, LUC enzyme activity analysis, and GFP signal detection. The DkMYB19 localized to the nucleus as well as the cytoplasm and DkMYB20 localized to the nucleus. The overexpression of miR858b led to the downregulation of and , which reduced the content of PA, whereas a reduction in miR858b activity upregulated and , resulting in a high content of PA in leaves transiently expressing a small tandem target mimic construct for blocking miR858 (STTM858b) . The transient transformation of miR858b in fruit discs also reduced the content of PA, while the content of PA increased under the transient transformation of fruit discs with STTM858b, , or . A similar phenomenon was observed upon the overexpression of miR858b in wild-type (WT) and or in persimmon leaf calli. These findings suggested that miR858b repressed the expression of and , which contributed to the PA accumulation in persimmon.