Molecular Analysis of Iron Deficiency Response in Hexaploid Wheat

Meng Wang,Yuta Kawakami,Navreet K Bhullar

doi:10.3389/fsufs.2019.00067

Meng Wang, Yuta Kawakami + Show 1 more

Open Access

https://doi.org/10.3389/fsufs.2019.00067

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Abstract

Iron deficiency leads to severe chlorosis in crop plants, including wheat, thereby reducing total yield and quality. Furthermore, grains of most bread wheat varieties are poor source of iron, which is vital for human nutrition. Despite the significance, iron uptake and translocation mechanisms in bread wheat have not been studied in detail, particularly under iron limited growth conditions. In this study, bread wheat plants were grown under iron deficiency stress until maturity. Data were collected at three distinct developmental time points during grain-filling. The plants experiencing low iron availability exhibited significantly lower chlorophyll content as well as low iron concentration in leaves and grains. The expression levels of bread wheat genes homologous to iron deficiency responsive genes of rice, barley, and Arabidopsis were significantly changed under iron deficiency stress. The wheat homologs of genes involved in phytosiderophore (PS) synthesis and transport were significantly up-regulated in the iron-deficient roots through all development stages, confirming an important role of deoxymugineic acid (DMA) in iron acquisition. The up-regulation of NICOTIANAMINE SYNTHASE (NAS) and DEOXYMUGINEIC ACID SYNTHASE (DMAS) in flag leaves and grains suggested the involvement of nicotianamine (NA) and DMA in iron chelation and translocation in wheat, particularly at the commencement of grain-filling. In line with this, the homolog of gene encoding TRANSPORTER OF MUGINEIC ACID (TOM) was up-regulated in the wheat roots under iron deficiency. Additionally, genes encoding long-distance iron transporter YELLOW STRIPE-LIKE (YSL), the vacuolar transporter NATURAL RESISTANCE ASSOCIATED MACROPHAGE PROTEIN (NRAMP), and the transcription factor BASIC HELIX-LOOP-HELIX (bHLH), were also up-regulated upon iron starvation. A tissue specific and growth stage specific gene expression differences in response to iron deficiency stress were observed, providing new insights into iron translocation, storage and regulation in bread wheat.

Highlights

Iron is an essential micronutrient for all living organisms
The chlorophyll content in flag leaves and metal concentration in roots, flag leaves and grains were measured in the iron deficiency stressed plants in comparison to the plants grown on normal condition
Several reports have shown that iron deficiency in rice, barley and maize increases the expression of genes involved in NA and deoxymugineic acid (DMA) synthesis (Negishi et al, 2002; Inoue et al, 2003, 2008; Kobayashi et al, 2005; Bashir et al, 2006; Zheng et al, 2009; Zhou et al, 2013)

Summary

Introduction

Iron is an essential micronutrient for all living organisms. In plants, iron functions as redox-active metal in many important reactions of metabolic processes such as photosynthesis, mitochondrial respiration, nitrogen assimilation, hormone biosynthesis, and the production and scavenging of reactive oxygen species (Hansch and Mendel, 2009). Iron deficiency causes interveinal chlorosis because of insufficient chlorophyll production that is often identified as alternate yellow and green stripes in younger leaves of most cereals (Barker and Stratton, 2015). Several studies investigated plant responses to iron deficiency stress and its effect on iron uptake, translocation and utilization (Thimm et al, 2001; Kobayashi et al, 2005; Buckhout et al, 2009; Yang et al, 2010; Rodriguez-Celma et al, 2013) but such information is rather limited for wheat (Bonneau et al, 2016; Beasley et al, 2017; Connorton et al, 2017; Garnica et al, 2018; Kumar et al, 2018; Mathpal et al, 2018)

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