Nitrogen and phosphorus interaction and cytokinin: responses of the primary root of Arabidopsis thaliana and the pdr1 mutant.

Nitrogen (N) and phosphorus (P) are the two most limiting nutrients for plant yield. Plants modify their metabolism and growth to cope with resources availability, consequently the integration of diverse signals is required. There is mounting evidence of N and P interaction, however, the sharing components of their signaling pathways have not been revealed yet. The pdr1 mutant has proved potentially useful in understanding the responses to nitrate (Ni), P and cytokinin. The mutation conferred pdr1 reduced root length in response to Ni under P deficiency and no effect of low cytokinin concentration. High N availability and high cytokinin caused strong root growth inhibition by different paths in wild type. Cytokinin repressed cell division, exhausted the quiescent center, caused changes in the pattern of AtPT1 expression and reduced AtACP5 expression. On the contrary, high N induced cell division as well as increased the expression of AtPT1 and AtACP5 even at high P availability. The data indicated interaction in the root modulation by N and P; and PDR1 is probably a signaling component of the nutritional status in Arabidopsis thaliana that modulates the response to N and P only partially mediated by cytokinin.