Nodule-Inception-Like Protein (NLP) Gene Family Identified in Physcomitrella Patens Genome Responds to Variable Nitrogen Supply

NODULE-INCEPTION-like proteins (NLPs) are plant specific transcription factors that play significant role in orchestrating nitrogen response. NLPs have been widely studied in vascular plants but very less is known about NLPs in non-vascular bryophytes till date. In current study, first, the in silico tools were employed for identification and characterization of NLPs in model bryophyte Physcomitrella patens genome. Furthermore, the expression profiles of PpNLPs were assessed under variable supply of nitrogen. A total of 6 Physcomitrella patens NLP genes (PpNLPs) were identified that shared resemblance in their physical and chemical attributes with Arabidopsis thaliana NLPs (AtNLPs). PpNLP genes possesses similarities in there iso-electric point and hydropathicity values with those of AtNLPs while gene lengths, protein lengths, and molecular weights were found higher in PpNLPs than AtNLPs. It was further observed that all PpNLPs, except PpNLP6, yield acidic hydrophilic proteins localized in nucleus and share a significant degree of homology in their gene structures and protein motifs with AtNLPs. Phylogenetic analysis indicated that PpNLPs possess significant evolutionary linkage with Arabidopsis thaliana, Oryza sativa, and Zea mays. Protein-protein interaction analysis suggested that PpNLPs possess substantial coordination with nitrogen responsive genes like nitrate reductase. Expressions of all PpNLPs were up-regulated in the availability of nitrate (5 and 10 mM) as sole nitrogen source while no significant increment was observed in the absence (0 mM) of nitrogen. The expression levels increased with increasing retention-time treatment of 0, 6, 12, 24, 48, and 72 hours. Results proposed that NLPs are responsive to as well as significantly regulated by nitrogen supply.

Rice PIN Auxin Efflux Carriers Modulate the Nitrogen Response in a Changing Nitrogen Growth Environment

Auxins play an essential role in regulating plant growth and adaptation to abiotic stresses, such as nutrient stress. Our current understanding of auxins is based almost entirely on the results of research on the eudicot Arabidopsis thaliana, however, the role of the rice PIN-FORMED (PIN) auxin efflux carriers in the regulation of the ammonium-dependent response remains elusive. Here, we analyzed the expression patterns in various organs/tissues and the ammonium-dependent response of rice PIN-family genes (OsPIN genes) via qRT–PCR, and attempted to elucidate the relationship between nitrogen (N) utilization and auxin transporters. To investigate auxin distribution under ammonium-dependent response after N deficiency in rice roots, we used DR5::VENUS reporter lines that retained a highly active synthetic auxin response. Subsequently, we confirmed that ammonium supplementation reduced the DR5::VENUS signal compared with that observed in the N-deficient condition. These results are consistent with the decreased expression patterns of almost all OsPIN genes in the presence of the ammonium-dependent response to N deficiency. Furthermore, the ospin1b mutant showed an insensitive phenotype in the ammonium-dependent response to N deficiency and disturbances in the regulation of several N-assimilation genes. These molecular and physiological findings suggest that auxin is involved in the ammonium assimilation process of rice, which is a model crop plant.