Effects of N, P, K and S on metabolism: new knowledge gained from multi-level analysis. Similarly, Fe homeostasis is also regulated in a PHR1-dependent manner.Īmtmann A., Armengaud P. Besides, PHO1 H3 is repressed by sufficient Zn supply, and the PHR1 and PHO1 proteins help to maintain the Pi–Zn homeostasis cross-talk. Likewise, Zn sufficiency inactivates the Zn-regulatory network and represses Zn transporters for Zn homeostasis. Also, ZIP2 and ZIP4 are activated by PHR1 binding to the P1BS sequences in the promoter of the genes. PHR1 acts as a regulator of P-transporters (PHT1 and PHO1) via the PHR1–miR399–PHO2 module. The arrow-heads and flat-ended lines indicate the positive and negative effects of PHR1, respectively. PHR1 also acts as a central regulator of sulfate transport ( SULTR1 3, SULTR2 1, and SULTR3 4). Transcriptional regulation of some of the genes involved in maintaining Fe and Zn homeostasis is PHR1-dependent it includes FER1 (encoding Fe storage protein ferritin) and ZIP2 and ZIP4 (zinc transporters). Other genes known to be involved in P-deficiency signaling/sensing include miR827 and miR399. At the molecular level, transcription factor PHR1 (initially identified as a key regulator of the phosphate-starvation induced genes) up-regulates phosphate transporters ( PHT1 1), PHO1 H1, and the genes involved in phosphate deficiency sensing/signaling ( SPX1, miR399, and miR827). The interactions between phosphorus (P), iron (Fe), sulfur (S), and zinc (Zn) homeostasis are indicated by ↔ arrows. Schematic representation of the macro‐ and micro-nutrient homeostasis. Thus, the phosphate-starvation response is attenuated by N-starvation because of the accumulation of negative regulators (SPXs and PHO2) and a decrease in the positive regulator (PHR1). PHO2 expression is down-regulated in response to +N by NIGT1/HHOs and CHL1/NRT1.1. On the contrary, PHR is positively regulated by +N.

SPXs transcription is directly repressed in response to +N by NIGT1/HHOs. OsSPX4 is degraded through 26S proteasome pathway in response to N supply (+N) via the action of OsNRT1.1B and an E3 ligase OsNBIP1 (NRT1−NBIP). miR399 represses PHO2, which acts in association with NLA (an E3 ligase) to repress/degrade PHO1 and PHT1. During P-starvation, PHR1 up-regulates the IPS1 and miR399 expression. PHR1 is negatively regulated by SPXs through inositol polyphosphate (insP)-triggered Pathway. PHR1 acts as a major transcriptional regulator of P-starvation response, which is accompanied by the activation of phosphate starvation-induced (PSI) genes followed by phosphate uptake and translocation by phosphate transporters (PHO1 and PHT1s). Schematic representation of nitrogen-starvation response and phosphate-starvation responses explaining N/P interactions. P-Fe-Zn tripartite interaction iron nutrient homeostasis nutrient interaction nutrient pathways interaction phosphorus sulfur zinc.Ĭopyright © 2021 Kumar, Kumar and Mohapatra. Integrated studies on pathways interactions/cross-talks between macro- and micro-nutrients in the agronomically important crop plants would be essential for sustainable agriculture around the globe, particularly under the changing climatic conditions. Identification of the important candidate genes for interactions between N, P, S, Fe, and/or Zn metabolic pathways might be useful for the breeders to improve nutrient use efficiency and yield/quality of crop plants. This review focuses on the recent advances in our understanding of how plants coordinate the acquisition, transport, signaling, and interacting pathways for N, P, S, Fe, and Zn nutrition at the molecular level. Similarly, light-responsive transcription factors were identified to be involved in modulating nutrient responses in Arabidopsis. Such studies on the nutrient interaction pathways suggest that an MYB-like transcription factor, phosphate starvation response 1 (PHR1), acts as a master regulator of N, P, S, Fe, and Zn homeostasis. Limited reports are available on the investigation of two-by-two or multi-level nutrient interactions in plants. Macro-nutrients like N, P, and/or S not only show the interacting pathways for each other but also affect micro-nutrient pathways. Plant responses to the deficiency of N, P, S, Fe, or Zn have been studied mainly as a separate event, and only a few reports discuss the molecular basis of biological interaction among the nutrients.

The deficiency of any of these nutrients may lead to defects in plant growth and decreased productivity. Nitrogen (N), phosphorus (P), sulfur (S), zinc (Zn), and iron (Fe) are some of the vital nutrients required for optimum growth, development, and productivity of plants.

Micro and macro nutrients plants