CsmiR396d targeting of <i>CsGS2</i> plays an important role in glutamine metabolism of tea plant (<i>Camellia sinensis</i>)

Nitrogen (N) is a critical element to improve tea production and quality. However, the role of miRNA in nitrogen nutrition of tea plants is still unclear. Glutamine, produced from assimilated nitrogen, plays a central role in the nitrogen cycle. In this study, 5' RNA ligase-mediated rapid-amplification of cDNA ends (5' RLM-RACE) and transient tobacco transformation experiments confirmed glutamine synthetase (CsGS2) was cleaved by CsmiR396d. Gene silencing and over-expression experiments of tea plant leaves show when CsmiR396d was over-expressed, the expression level of CsGS2 and the content of glutamine were decreased; when miR396d was silenced, the expression level of CsGS2 and the content of glutamine were increased. The results of the over-expression experiment in Arabidopsis was consistent with those in tea leaves. These results revealed the regulatory role of CsmiR396d in nitrogen nutrition of tea plant, which will provide further information and theoretical basis for tea plant utilization and quality improvement.