Physiological and molecular investigations on a high-yielding variety and near-isogenic line of rice under continuous phosphorus stress reveal major regulatory function of Pup1 QTL.

Phosphorous (P) plays crucial roles in cellular functioning including respiration, photosynthesis, and membranes. P deficiency in the soil causes stunted growth, smaller/erect leaves, lesser tillers, and a considerable decrease in yield. To decipher the functions of Pup1 QTL and delineate the potential effects of continuous P stress on plant growth, yield/quality, physio-biochemical and molecular analyses of rice [Pusa-44 (P deficiency sensitive) and a near-isogenic line-23 (NIL-23), (harbouring Pup1 QTL, tolerant genotype)] were hydroponically grown under P continuous stress [deficiency (4 ppm) or extravagance (≥32 ppm)] till maturity. Decrease in the number of tillers and panicles under stress led to poor agronomic performance of rice. P concentration in roots, leaves, and seeds raised significantly with increasing concentration of P in hydroponic culture. Higher P concentration in the medium led to elevated phytate concentration in seeds; however, it was comparatively more in seeds of the tolerant (NIL-23) genotype. Comparative transcriptome analysis indicated differential expression of genes for P transporters and those implicated in P mobilization/homeostasis, carbohydrate/lipid metabolism, etc. on P deficiency. Moreover, the regulatory function of Pup1 in reprograming the gene expression involved in chromatin assembly, histone/DNA methylation, cell wall organization, etc. was detected in the panicle of tolerant genotype on P deficiency. This study confirms a major regulatory function of Pup1 and outlines the potential effects of excessive P on plant development, productivity, and quality of seeds. These findings would be useful in improving P uptake/use efficiency in rice and prudent/sustainable usage of phosphatic fertilizers.