Transcriptional Regulation of Genes Involved in Zinc Uptake, Sequestration and Redistribution Following Foliar Zinc Application to Medicago sativa.

Alessio Cardini,Laura Ercoli,Barbara Mazzolai,Philip J White,Elisa Pellegrino,Marco C Mascherpa

doi:10.3390/plants10030476

Abstract

Zinc (Zn) is an essential micronutrient for plants and animals, and Zn deficiency is a widespread problem for agricultural production. Although many studies have been performed on biofortification of staple crops with Zn, few studies have focused on forages. Here, the molecular mechanisms of Zn transport in alfalfa (Medicago sativa L.) were investigated following foliar Zn applications. Zinc uptake and redistribution between shoot and root were determined following application of six Zn doses to leaves. Twelve putative genes encoding proteins involved in Zn transport (MsZIP1-7, MsZIF1, MsMTP1, MsYSL1, MsHMA4, and MsNAS1) were identified and changes in their expression following Zn application were quantified using newly designed RT-qPCR assays. These assays are the first designed specifically for alfalfa and resulted in being more efficient than the ones already available for Medicago truncatula (i.e., MtZIP1-7 and MtMTP1). Shoot and root Zn concentration was increased following foliar Zn applications ≥ 0.1 mg plant−1. Increased expression of MsZIP2, MsHMA4, and MsNAS1 in shoots, and of MsZIP2 and MsHMA4 in roots was observed with the largest Zn dose (10 mg Zn plant−1). By contrast, MsZIP3 was downregulated in shoots at Zn doses ≥ 0.1 mg plant−1. Three functional gene modules, involved in Zn uptake by cells, vacuolar Zn sequestration, and Zn redistribution within the plant, were identified. These results will inform genetic engineering strategies aimed at increasing the efficiency of crop Zn biofortification.

Highlights

IntroductionA large proportion of the world’s population suffers from Zn-related diseases (i.e., malabsorption syndrome, liver disease, chronic renal disease, sickle cell disease, and other chronic diseases), since they rely on cereal-based diets with low Zn content due to poor soil Zn availability [1,2,3,4]
A large proportion of the world’s population suffers from Zn-related diseases, since they rely on cereal-based diets with low Zn content due to poor soil Zn availability [1,2,3,4]
Animals can suffer from Zn deficiencies that could be alleviated by biofortified feed or Zn supplementation, improving livestock health and quality of food products, which affect human health indirectly [5,6,7,8]

Summary

Introduction

A large proportion of the world’s population suffers from Zn-related diseases (i.e., malabsorption syndrome, liver disease, chronic renal disease, sickle cell disease, and other chronic diseases), since they rely on cereal-based diets with low Zn content due to poor soil Zn availability [1,2,3,4]. Diversification of the human diet and biofortification of edible crops are needed to alleviate Zn deficiency in humans. Animals can suffer from Zn deficiencies that could be alleviated by biofortified feed or Zn supplementation, improving livestock health and quality of food products, which affect human health indirectly [5,6,7,8]. Zinc is involved in various physiological functions, such as CO2 fixation, protein synthesis, free radical capture, regulation of growth and development, and disease resistance [9,10]. Many structural motifs in transcriptional regulatory proteins are stabilized by Zn, such as Zn finger domains [11]. Zinc deficiency reduces crop production, as does

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