Effects of Deficiency and Excess of Zinc on Morphophysiological Traits and Spatiotemporal Regulation of Zinc-Responsive Genes Reveal Incidence of Cross Talk between Micro- and Macronutrients

Abstract

Zinc (Zn) is an essential micronutrient which affects plant growth and development in deficiency and can be toxic when present in excess. In Arabidopsis thaliana , different families of cation transporters play pivotal roles in Zn homeostasis. In the present study, we evaluated the effects of Zn in its deficiency (0 μM; Zn-) and excess (75 μM; Zn++) on various morphophysiological and molecular traits. Primary root length was reduced in Zn- seedlings, whereas there were significant increases in the number and length of lateral roots under Zn- and Zn++ conditions, respectively. Concentration of various macro- and microelements showed variations under different Zn regimes and notable among them was the reduced level of iron (Fe) in Zn++ seedlings compared to Zn+. Certain members of the ZIP family (ZIP4, ZIP9, and ZIP12) showed significant induction in roots and shoots of the Zn- seedlings. Their suppression under Zn++ condition indicated their transcriptional regulation by Zn and their roles in the maintenance of its homeostasis. Zn-deficiency-mediated induction of HMA2 in roots and shoots suggested its role in effluxing Zn into xylem for long-distance transport. Attenuation in the expression of Fe-responsive FRO2 and IRT1 in Zn- roots and their induction in Zn++ roots provided empirical evidence toward the prevalence of a cross talk between Zn and Fe homeostasis. Variable effects of Zn- and Zn++ on the expression of subset of genes involved in the homeostasis of phosphate (Pi), potassium (K), and sulfur (S) further highlighted the prevalence of cross talk between the sensing and signaling cascades of Zn and macronutrients. Further, the inducibility of ZIP4 and ZIP12 in response to cadmium (cd) treatment could be harnessed by tailoring them in homologous or heterologous plant system for removing pollutant toxic heavy metals from the environment.

Phosphate/Zinc Interaction Analysis in Two Lettuce Varieties Reveals Contrasting Effects on Biomass, Photosynthesis, and Dynamics of Pi Transport

“…Huang et al, 2000 have provided evidence for the involvement of the high affinity Pi transporter (PHT) in the increase of Pi uptake in barley Pi-deficient plants. These results [11, 12] showed that Zn deficiency could induce the expression of the PHT1;1 in Arabidopsis. Recently, genes that are necessary for the increase in Pi overaccumulation in response to Zn deficiency in Arabidopsis have been identified, namely, the Pi exporter PHO1 and its homologue PHO1;H3 [12].…”

Comprehensive study of excess phosphate response reveals ethylene mediated signaling that negatively regulates plant growth and development

“…These variations may be due to the use of different growth conditions such as light, sucrose, incubation time 51, 52 . Also, the concentration of P i 23, 24 and, the use of the various gelling media possessing varying levels of P i contamination may attribute to these variations 52, 53 . Ethylene is known to reduce primary root length under P i -sufficient condition 54–56 .…”

“…The nutrient composition of P, Fe, Zn, Mn and Ca plays a crucial role in determining RSA plasticity 24, 53 . Earlier studies reported that the micronutrients deficiency in plants caused by high P condition 19, 20, 47, 48 .…”

Heavy Metals Induce Iron Deficiency Responses at Different Hierarchic and Regulatory Levels

“…In the case of Zn, changes in root traits depended more strongly on the applied Zn dose. Lower concentrations of Zn induced lateral root elongation and caused no further changes in RSA (Jain et al, 2013), while higher concentrations inhibited both primary and lateral root growth (Fukao et al, 2011;Richard et al, 2011). However, so far, root architectural responses have always been analyzed separately under Fe deficiency or metal excess (Lequeux et al, 2010;Giehl et al, 2012;Gruber et al, 2013;Jain et al, 2013;Yuan et al, 2013).…”