Influence of nitrogen on the expression of TaDof1 transcription factor in wheat and its relationship with photo synthetic and ammonium assimilating efficiency.

Nitrogen is a crucial macronutrient needed in the greatest amount of all mineral elements required by plants. Development of crop varieties with high nitrogen use efficiency (NUE) is imperative for sustainable agriculture. Understanding how plant genes respond to different nitrogen conditions is essential for formulating approaches, for manipulating genes, for improving NUE. In the present study we analyzed the activity of three different enzymes involved in nitrogen assimilation viz., GS, GOGAT and GDH along with physiological parameters like chlorophyll variable yield (Fv/Fmax), photosynthesis rate and total chlorophyll content at four different growth stages of wheat plant development under different nitrogen treatments. For this study two different wheat varieties UP-2644 and Raj-4097 having high and low protein content, respectively in the grains were chosen. Gene expression profile of a Dof transcription factor (TaDof1 of wheat) was also included in the study to assess its role in nitrogen metabolism. Densitometry analysis at S(2) and S(3) stage of wheat spikes of both the wheat varieties grown at different nitrogen treatments showed that TaDof1 expression was up-regulated in low nitrogen treatment. In S(3) stage, in high protein content wheat variety UP-2644, TaDof1 expression was elevated in low and normal nitrogen treatment as compared to high nitrogen treatment. The gene expression profile of Dof 1 was found to coincide with the enzyme activities of GS, GOGAT at the S(3) stage. The activities of these enzymes were prolonged in the high protein content variety. Since, Dof transcription factor(s) have been previously reported to control the expression of genes involved nitrogen assimilation i.e., GS and GOGAT and may be the elevated expression of Dof 1 at the grain filling stage over expresses the GS and GOGAT genes thereby prolonging their activities.