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

Abstract

Iron (Fe) is a limiting factor in crop growth and nutritional quality because of its low solubility. However, the current understanding of how major crops respond to Fe deficiency and the genetic basis remains limited. In the present study, Fe-efficient inbred line Ye478 and Fe-inefficient inbred line Wu312 and their recombinant inbred line (RIL) population were utilized to reveal the physiological and genetic responses of maize to low Fe stress. Compared with the Fe-sufficient conditions (+Fe: 200 μM), Fe-deficient supply (−Fe: 30 μM) significantly reduced shoot and root dry weights, leaf SPAD of Fe-efficient inbred line Ye478 by 31.4, 31.8, and 46.0%, respectively; decreased Fe-inefficient inbred line Wu312 by 72.0, 45.1, and 84.1%, respectively. Under Fe deficiency, compared with the supply of calcium nitrate (N1), supplying ammonium nitrate (N2) significantly increased the shoot and root dry weights of Wu312 by 37.5 and 51.6%, respectively; and enhanced Ye478 by 23.9 and 45.1%, respectively. Compared with N1, N2 resulted in a 70.0% decrease of the root Fe concentration for Wu312 in the −Fe treatment, N2 treatment reduced the root Fe concentration of Ye478 by 55.8% in the −Fe treatment. These findings indicated that, compared with only supplying nitrate nitrogen, combined supply of ammonium nitrogen and nitrate nitrogen not only contributed to better growth in maize but also significantly reduced Fe concentration in roots. In linkage analysis, ten quantitative trait loci (QTLs) associated with Fe deficiency tolerance were detected, explaining 6.2–12.0% of phenotypic variation. Candidate genes considered to be associated with the mechanisms underlying Fe deficiency tolerance were identified within a single locus or QTL co-localization, including ZmYS3, ZmPYE, ZmEIL3, ZmMYB153, ZmILR3 and ZmNAS4, which may form a sophisticated network to regulate the uptake, transport and redistribution of Fe. Furthermore, ZmYS3 was highly induced by Fe deficiency in the roots; ZmPYE and ZmEIL3, which may be involved in Fe homeostasis in strategy I plants, were significantly upregulated in the shoots and roots under low Fe stress; ZmMYB153 was Fe-deficiency inducible in the shoots. Our findings will provide a comprehensive insight into the physiological and genetic basis of Fe deficiency tolerance.

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

“…Furthermore, ZmILR3, together with ZmBTS (GRMZM2G320399) which encodes a putative E3 ligase protein and was identified in qFe(II)-R/S6-1, may be both involved in the PYE network that could be another transcriptional regulatory network in addition to the FIT network. It should be noted that no QTLs detected on the supply of Fe(III) reported by Xu et al (2022), were co-localized with the QTLs containing strategy I genes in the current study, which only utilized Fe(II). Moreover, only strategy II gene ZmYS3 was identified in the co-localization of one of our previously reported locus and three QTLs detected in this study.…”

“…Moreover, Fe deficiency-inducible genes, such as ZmTOM1, ZmDMAS1, and ZmIRT1, are upregulated in the roots of ys1 and ys3 mutant under Fe-sufficient condition, suggesting that ys1 and ys3 plants are Fe-deficient during growth in the presence of Fe (Nozoye et al, 2013). Another research showed that ZmYS3 which was identified by the linkage analysis in the Ye478 × Wu312 RIL population on the supply of Fe(III) (Xu et al, 2022), was only expressed in the roots and displayed a significant regulation under Fe deficiency.…”

“…BRUTUS (BTS) could integrate local and long-distance iron signaling pathways, might negatively affect the PYE network (Cointry and Vert, 2019). Xu et al (2022) found that ZmPYE was significantly induced by Fe deficiency in the shoots and roots in maize. In this study, ZmBTS displayed a greater upregulation in Fe-deficient shoots than in Fe-deficient roots of maize inbred lines, and a greater regulation in Fe-efficient inbred line rather than in Fe-inefficient inbred line (Figures 9C,D).…”

Genome-wide diversity in lowland and highland maize landraces from southern South America: population genetics insights to assist conservation

“…Indeed, on chromosome 3, this region includes the ys3 gene (Zm00001d041111, GRMZM2G063306), which has been shown to be under selection in Z. mays ssp. parviglumis (Aguirre-Liguori et al, 2017), and involved in iron homeostasis (Xu et al, 2022; Nozoye et al, 2013), a trait potentially important in the distinctive lateritic, iron-rich, red soils of NEA (Píccolo et al, 1998). Furthermore, the regions identified on chromosomes 7 and 10 (Supplementary table 8B) overlap with genomic tracts of Z. mays ssp.…”

Meta-Quantitative Trait Loci Analysis and Candidate Gene Mining for Drought Tolerance-Associated Traits in Maize (Zea mays L.)

“…Their homologous rice drought tolerance gene is OsEIL2, which confers abiotic stress sensitivity by regulating OsBURP16 [83]. Xu et al [84] identified Zm00001d028974 (ZmEIL3) as a candidate gene related to iron deficiency tolerance.…”