Interaction Between Macro‐ and Micro-Nutrients in Plants

Abstract

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. The deficiency of any of these nutrients may lead to defects in plant growth and decreased productivity. 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. Macro-nutrients like N, P, and/or S not only show the interacting pathways for each other but also affect micro-nutrient pathways. Limited reports are available on the investigation of two-by-two or multi-level nutrient interactions in plants. 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. Similarly, light-responsive transcription factors were identified to be involved in modulating nutrient responses in Arabidopsis. 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. 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. 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.

Cross-Talks Between Macro- and Micronutrient Uptake and Signaling in Plants

“…This demonstrated that specific nutrient-deficiency response signaling (such as induction of FIT in double S and Fe deficiencies) can control this cross-regulation. On the other hand, fewer S-or Fedeficiency-responsive genes were co-regulated in response to the K deficiency, while the genes involved in the S and Fe assimilation 5) Zn transport and homeostasis are also involved in a PHR1-dependent manner; under Pi starvation, PHR1 positively regulates the expression of zinc transporter genes ZIP2 and ZIP4 through binding to the P1BS cis-elements in these gene promoters (Briat et al, 2015;Kumar et al, 2021; see following Figure 3A). The arrows and flat-ended lines indicate the positive and negative influences, respectively.…”

“…Furthermore, the nitrate-inducible GARP-type transcriptional repressor 1 (NIGT1) proteins bind to and repress the promoters of SPX genes in Arabidopsis to modulate the PHR activity, PHT1;1 expression, and Pi acquisition (Ueda et al, 2020; also see Figure 2). Finally, these findings are summarized as follows: (i) N application increases the PHR1 protein stability in plants (Medici et al, 2019;Kumar et al, 2021); (ii) NRT1.1 interacts with SPX to degrade the SPX protein during nitrate supply (Hu et al, 2019;Kumar et al, 2021); and (iii) the nitrate-NIGT1-SPX-PHR1-PHT1 signaling is the key regulatory pathway that mediates Pi uptake in response to N availability (Ueda et al, in press). These molecular actors that integrate N and P signals into crops may have implications in biotechnology and agricultural practices.…”

“…The role of PHR1 in the coordination of Pi-Zn homeostasis has been demonstrated (Khan et al, 2014), while the expression of PHT1 and PHO1 genes is essential for Pi uptake and accumulation in plants through the Pi regulatory-signaling pathway (PHR1-miR399-PHO2) (Fujii et al, 2005;Aung et al, 2006;Bari et al, 2006;Chiou et al, 2006;Khan et al, 2014;Liu et al, 2014). In addition, the P-starvation-signaling PHR1-P1BS module in both roots and shoots leads to the Zn overaccumulation in plants as this module upregulates the ZIP2 subfamily genes belonging to the ZIP family (Briat et al, 2015;Kumar et al, 2021). Moreover, these authors proposed that plant ZIP2 and ZIP4 genes may be transcriptionally induced via the activated PHR1 transcription factor (Briat et al, 2015;Kumar et al, 2021).…”

“…In addition, the P-starvation-signaling PHR1-P1BS module in both roots and shoots leads to the Zn overaccumulation in plants as this module upregulates the ZIP2 subfamily genes belonging to the ZIP family (Briat et al, 2015;Kumar et al, 2021). Moreover, these authors proposed that plant ZIP2 and ZIP4 genes may be transcriptionally induced via the activated PHR1 transcription factor (Briat et al, 2015;Kumar et al, 2021). This proposition is consistent with our finding that at least one P1BS (GNATATNC) cis-element, which is directly bound by the PHR1, is present in the promoter regions of plant ZIP2 subfamily genes (see Figure 3A), implying that Zn transporter ZIP2 may regulate plant Zn homeostasis in a phosphorus-dependent manner.…”

“…Recently, some studies have revealed that the MYB transcription factor, such as PHR1, regulated the genes essential for Pi, Zn, and Fe uptake and homeostasis in plants (Rouached et al, 2011;Bournier et al, 2013;Khan et al, 2014;Briat et al, 2015;Kumar et al, 2021). Therefore, PHR1 acts as the first common regulator of Pi, Zn, and Fe homeostasis and serves as an integrator of multiple mineral signals in plants (Briat et al, 2015; see Figures 3, 4).…”