Light regulation of nitrate reductase gene expression and enzyme activity in the leaves of mulberry

Nitrate reductase (NR) is considered to be an essential enzyme in plants, as it catalyses the conversion of nitrate to nitrite. In mulberry (Morus spp.), a plant of sericultural importance, the NR enzyme activity is found to be regulated by light. Three mulberry genotypes used in the present study showed that the NR enzyme activity increased in response to light. To identify whether light also regulates NR gene at the transcriptional level the expression of NR mRNA has been studied. The analysis of NR gene expression showed that light plays a significant role in regulating the NR gene with basal or no expression in response to light during the day while it is found to increase in the dark during the night showing maximum expression at pre-dawn hours.