Cs-miR156 is involved in the nitrogen form regulation of catechins accumulation in tea plant (Camellia sinensis L.)

The nitrogen source affects the growth of tea plants and regulates the accumulation of catechins in the leaves. In this report, we assessed the influences of NH4+ and NO3− on plant growth, catechins accumulation and associated gene expression. Compared with the preferential nitrogen source NH4+, when NO3− was supplied as the sole nitrogen source, tea plants showed similar symptoms with the nitrogen-free treatments and showed lower nitrogen, free amino acid accumulation, chlorophyll content and biomass gain, indicating NO3− was not efficiently used by these plants. However, the total shoot catechins content was significantly higher for NO3− treatments than that for NH4+ treatment or combined NH4++NO3− treatment, suggesting that, in addition to its influence on plant growth, the nitrogen form regulated the accumulation of catechins in tea. The expression of catechins biosynthesis-related genes was associated with the regulation of catechins accumulation and composition changes mediated by nitrogen form. PAL, CHS, CHI, and DFR genes exhibited higher expression levels in plants supplied with NO3−, in which the transcript level of DFR in the shoots was significantly correlated with the catechins content. In the end, we identified a new function for the Cs-miR156, which was drastically induced through NH4+. Moreover, a potential mechanism of the Cs-miR156 pathway in regulating catechins biosynthesis in tea plants has been suggested, with particular respect to nitrogen forms. Cs-miR156 might repress the expression of the target gene SPL to regulate the DFR gene, which plays a vital role in catechins biosynthesis.