The auxin signaling pathway contributes to phosphorus-mediated zinc homeostasis in maize

Abstract

Although the interaction between P and Zn has long been recognized in plants, the physiological and molecular mechanisms underlying P and Zn interactions are poorly understood. We show here that P supply decreases the Zn concentration in maize shoots and roots. Compared to +P + Zn (addition of both P and Zn), +P-Zn reduced and -P-Zn increased the total length of 1° lateral roots (LRs). Under +P + Zn, both P and Zn concentrations were lower in the sl1 mutant roots than in wild-type (WT) maize roots, and P accumulation did not reduce the Zn concentration in ll1 mutant roots. Transcriptome profiling showed that the auxin signaling pathway contributed to P-mediated Zn homeostasis in maize. Auxin production and distribution were altered by changes in P and Zn supply. Cytosolic Zn co-localized with auxin accumulation under +P + Zn. Exogenous application of 1-NAA and L-Kyn altered the P-mediated root system architecture (RSA) under Zn deficiency. -P-Zn repressed the expression of miR167. Overexpression of ZmMIR167b increased the lengths of 1° LRs and the concentrations of P and Zn in maize. These results indicate that auxin-dependent RSA is important for P-mediated Zn homeostasis in maize.HighlightAuxin-dependent RSA is important for P-mediated Zn homeostasis in maize.

Recent advances in unraveling the mystery of combined nutrient stress in plants

“…Further analysis revealed a novel binding motif (GTGTCGAA) that binds to the transcription factor bZIP23, which is associated with Zn deficiency response (Kisko et al, 2018). Interestingly, Wang et al (2023) found recently that in maize, Pi concentration affects Zn concentration before Zn affects Pi. This may be due at least in part to Pi application increasing plant mass and thus decreasing Zn concentration by dilution.…”

“…This may be due at least in part to Pi application increasing plant mass and thus decreasing Zn concentration by dilution. It is, however, a point for experimental design regarding Pi‐Zn homeostasis (Wang et al., 2023).…”

“…The free content of the common auxin indole‐3‐acetic acid (IAA) at sites of emerging lateral roots was found to be lowest in −Pi/−Zn conditions and highest under +P/−Zn. Fluorescent tagging shows cytosolic Zn colocalizes with free IAA at the vascular connection with the parent root under +Pi/+Zn but not under −Pi/−Zn (Wang et al., 2023).…”

“…In many plant species, a deficiency in Zn leads to an overaccumulation of P (Wang et al., 2023). This phenomenon has been attributed to the regulation of Pi transporters by Zn (Huang et al., 2000).…”

“…Interestingly, Wang et al. (2023) found recently that in maize, Pi concentration affects Zn concentration before Zn affects Pi. This may be due at least in part to Pi application increasing plant mass and thus decreasing Zn concentration by dilution.…”