OsPHR3 affects the traits governing nitrogen homeostasis in rice

BACKGROUND: Phosphate (Pi) and Nitrogen (N) are essential macronutrients required for plant growth and development. In Arabidopsis thaliana (Arabidopsis), the transcription factor PHR1 acts as a Pi central regulator. PHL1 is a homolog of PHR1 and also plays a role in maintaining Pi homeostasis. In rice (Oryza sativa), OsPHR1–4 are the orthologs of PHR1 and have been implicated in regulating sensing and signaling cascades governing Pi homeostasis. RESULTS: Here the role of OsPHR3 was examined in regulating the homeostasis of N under different Pi regimes. Deficiencies of different variants of N exerted attenuating effects on the relative expression levels of OsPHR3 in a tissue-specific manner. For the functional characterization of OsPHR3, its Tos17 insertion homozygous mutants i.e., osphr3–1, osphr3–2, and osphr3–3 were compared with the wild-type for various morphophysiological and molecular traits during vegetative (hydroponics with different regimes of N variants) and reproductive (pot soil) growth phases. During vegetative growth phase, compared with the wild-type, OsPHR3 mutants showed significant variations in the adventitious root development, influx rates of (15)N-NO(3)(−) and (15)N-NH(4)(+), concentrations of total N, NO(3)(−) and NH(4)(+) in different tissues, and the relative expression levels of OsNRT1.1a, OsNRT2.4, OsAMT1;1, OsNia1 and OsNia2. The effects of the mutation in OsPHR3 was also explicit on the seed-set and grain yield during growth in a pot soil. Although Pi deficiency affected total N and NO(3)(−) concentration, the lateral root development and the relative expression levels of some of the NO(3)(−) and NH(4)(+) transporter genes, its availability did not exert any notable regulatory influences on the traits governing N homeostasis. CONCLUSIONS: OsPHR3 plays a pivotal role in regulating the homeostasis of N independent of Pi availability. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12870-018-1462-7) contains supplementary material, which is available to authorized users.