LNC159c Negatively Regulates Anthocyanin Biosynthesis via miR159c in Malus spectabilis Under Low Nitrogen

Low-nitrogen (LN) conditions typically promote anthocyanin biosynthesis in plants. Although previous studies primarily explored structural genes and transcription factors involved in anthocyanin biosynthesis, the role of long noncoding RNAs (lncRNAs) in this process under LN conditions remains less understood. This study identified LNC159c as a potential regulator of anthocyanin biosynthesis, with its expression notably downregulated under LN conditions. LNC159c functions as the host gene of miR159c, which regulates its expression. A dual-luciferase reporter assay and GFP signal detection demonstrated that miR159c inhibited MsMYB10 expression through base complementary pairing. Yeast one-hybrid (Y1H) and dual-LUC reporter assays jointly verified that MsMYB10 binds to the F3'H promoter. Stable overexpression in apple calli and transient overexpression in apple fruit peels and M. spectabilis leaves showed that LNC159c overexpression promoted miR159c expression, while inhibiting MsMYB10 expression and anthocyanin biosynthesis. MsMYB10 overexpression promoted anthocyanin biosynthesis, whereas the opposite results were observed in MsMYB10-silenced tissues. Thus, under LN conditions, reduced LNC159c expression limits miR159c production, relieving MsMYB10 inhibition and enhancing anthocyanin accumulation. These findings highlight the regulatory role of lncRNAs in anthocyanin biosynthesis under LN conditions.