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

摘要

Zinc (Zn) is an essential micronutrient whichrnaffects plant growth and development in deficiency and can berntoxic when present in excess. in Arabidopsis thaliana, differentrnfamilies of cation transporters play pivotal roles in Znrnhomeostasis. in the present study, we evaluated the effects ofrnZn in its deficiency (0 μM; Zn-) and excess (75 μM; Zn++) onrnvarious morphophysiological and molecular traits. Primary rootrnlength was reduced in Zn- seedlings, whereas there werernsignificant increases in the number and length of lateral rootsrnunder Zn- and Zn++ conditions, respectively. Concentration ofrnvarious macro- and microelements showed variations underrndifferent Zn regimes and notable among them was the reducedrnlevel of iron (Fe) in Zn++ seedlings compared to Zn+. Certainrnmembers of the ZiP family (ZIP4, ZIP9, and ZIP 12) showed significant induction in roots and shoots of the Zn- seedlings.rnTheir suppression under Zn++ condition indicated their transcriptional regulation by Zn and their roles in the maintenance of itsrnhomeostasis. Zn-deficiency-mediated induction of HMA2 in roots and shoots suggested its role in effluxing Zn into xylem forrnlong-distance transport Attenuation in the expression of Fe-responsive FRO2 and IRT1 in Zn- roots and their induction in Zn+rn+ roots provided empirical evidence toward the prevalence of a cross talk between Zn and Fe homeostasis. Variable effects ofrnZn- and Zn++ on the expression of subset of genes involved in the homeostasis of phosphate (Pi), potassium (K), and sulfurrn(S) further highlighted the prevalence of cross talk between the sensing and signaling cascades of Zn and macronutrients.rnFurther, the inducibility of ZIP4 and ZIP12 in response to cadmium (cd) treatment could be harnessed by tailoring them inrnhomologous or heterologous plant system for removing pollutant toxic heavy metals from the environment.