Mapping of the Quantitative Trait Loci and Candidate Genes Associated With Iron Efficiency in Maize

Abstract

Iron (Fe) is a mineral micronutrient for plants, and Fe deficiency is a major abiotic stress in crop production because of its low solubility under aerobic and alkaline conditions. In this study, 18 maize inbred lines were used to preliminarily illustrate the physiological mechanism underlying Fe deficiency tolerance. Then biparental linkage analysis was performed to identify the quantitative trait loci (QTLs) and candidate genes associated with Fe deficiency tolerance using the recombinant inbred line (RIL) population derived from the most Fe-efficient (Ye478) and Fe-inefficient (Wu312) inbred lines. A total of 24 QTLs was identified under different Fe nutritional status in the Ye478 × Wu312 RIL population, explaining 6.1–26.6% of phenotypic variation, and ten candidate genes were identified. Plants have evolved two distinct mechanisms to solubilize and transport Fe to acclimate to Fe deficiency, including reduction-based strategy (strategy I) and chelation-based strategy (strategy II), and maize uses strategy II. However, not only genes involved in Fe homeostasis verified in strategy II plants (strategy II genes), which included ZmYS1, ZmYS3, and ZmTOM2, but also several genes associated with Fe homeostasis in strategy I plants (strategy I genes) were identified, including ZmFIT, ZmPYE, ZmILR3, ZmBTS, and ZmEIN2. Furthermore, strategy II gene ZmYS1 and strategy I gene ZmBTS were significantly upregulated in the Fe-deficient roots and shoots of maize inbred lines, and responded to Fe deficiency more in shoots than in roots. Under Fe deficiency, greater upregulations of ZmYS1 and ZmBTS were observed in Fe-efficient parent Ye478, not in Fe-inefficient parent Wu312. Beyond that, ZmEIN2 and ZmILR3, were found to be Fe deficiency-inducible in the shoots. These findings indicate that these candidate genes may be associated with Fe deficiency tolerance in maize. This study demonstrates the use of natural variation to identify important Fe deficiency-regulated genes and provides further insights for understanding the response to Fe deficiency stress in maize.

Identification of Quantitative Trait Loci Associated With Iron Deficiency Tolerance in Maize

“…In this study, qFe(III)-PH7-1 controlling plant height was co-localized with qFe(III)-RDW7-1 for root dry weight on Chromosome 7. Besides, another two loci in this study were co-localized with the loci identified in the Ye478 × Wu312 RIL population on the supply of Fe(III)-EDTA ( Xu et al, 2022 ). On Chromosome 3, qFe(III)-PH3-1 detected on deficient supply of Fe(III)-EDTA in this study was co-localized with three loci [ qFe(II)-PH3-1 , qFe(II)-SDW3-1 , and qFe(II)-R/S3-1 ] detected on the supply of ferrous iron.…”

“… Ten quantitative trait loci associated with Fe deficiency tolerance detected on Chromosomes 1, 2, 3, 5, and 7 in the Ye478 × Wu312 recombinant inbred line (RIL) population and the co-localizations identified in the same population on the supply of Fe(III)-EDTA ( Xu et al, 2022 ). Important candidate genes ( ZmYS3 , ZmHMA1 , ZmHMA2 , ZmHMA7 , ZmNAS2 , ZmNAS4 , ZmPYE , and ZmEIL3 ) are depicted in gray columns.…”

Genome-Wide Association Analysis Reveals the Genetic Basis of Iron-Deficiency Stress Tolerance in Maize

“…GRMZM2G111300, which encodes another member of ZIP (ZRT/IRT-like protein) family, was localized in the 25.9 kb upstream of chr4.S_26684019 on chromosome 4. GRMZM2G171616, encoding an EIN3-binding F-Box protein that may be involved in the regulation of ethylene signaling and Fe homeostasis in strategy I plants, was identified within the co-localization of chr9.S_90366645 and qFe(II)-SPAD9-1 which is another locus mapped on chromosome 9 in the Ye478 × Wu312 RIL population reported by Xu et al ( 2022 ).…”

“…GRMZM2G096958, also known as ZmNAAT1 which encodes nicotianamine aminotransferase, was containing the SNP chr4.S_219582768 that is significantly correlated with R/S ratio under Fe deficiency. GRMZM5G812538 also known as ZmYSL11 encoding a yellow stripe-like transporter, was identified within the overlapped regions co-localized by chr10.S_131843508 and qFe(II)-SPAD10-2 which is a reported QTL controlling leaf SPAD detected in the Ye478 × Wu312 RIL population under Fe deficiency (Xu et al, 2022 ).…”