Identification and Analysis of Zinc Efficiency-Associated Loci in Maize

Abstract

Zinc (Zn) deficiency, a globally predominant micronutrient disorder in crops and humans, reduces crop yields and adversely impacts human health. Despite numerous studies on the physiological mechanisms underlying Zn deficiency tolerance, its genetic basis of molecular mechanism is still poorly understood. Thus, the Zn efficiency of 20 maize inbred lines was evaluated, and a quantitative trait locus (QTL) analysis was performed in the recombination inbred line population derived from the most Zn-efficient (Ye478) and Zn-inefficient inbred line (Wu312) to identify the candidate genes associated with Zn deficiency tolerance. On this basis, we analyzed the expression of ZmZIP1-ZmZIP8. Thirteen QTLs for the traits associated with Zn deficiency tolerance were detected, explaining 7.6–63.5% of the phenotypic variation. The genes responsible for Zn uptake and transport across membranes (ZmZIP3, ZmHMA3, ZmHMA4) were identified, which probably form a sophisticated network to regulate the uptake, translocation, and redistribution of Zn. Additionally, we identified the genes involved in the indole-3-acetic acid (IAA) biosynthesis (ZmIGPS) and auxin-dependent gene regulation (ZmIAA). Notably, a high upregulation of ZmZIP3 was found in the Zn-deficient root of Ye478, but not in that of Wu312. Additionally, ZmZIP4, ZmZIP5, and ZmZIP7 were up-regulated in the Zn-deficient roots of Ye478 and Wu312. Our findings provide a new insight into the genetic basis of Zn deficiency tolerance.

Identification of Zinc Efficiency-Associated Loci (ZEALs) and Candidate Genes for Zn Deficiency Tolerance of Two Recombination Inbred Line Populations in Maize

“…In addition, Zn concentration of the sensitive inbred line K22 was 2.2-fold and 1.4-fold higher than those of tolerant inbred lines BY815 and DAN340, respectively, indicating that Zn-efficient genotypes may not necessarily have higher shoot Zn concentrations when compared with Zn-inefficient genotypes. Furthermore, our previous results confirmed that Zn efficiencies based on shoot and root dry weights were not correlated with Zn concentrations in the shoot and root of twenty maize inbred lines which contained K22, BY815, and DAN340 [25]. Zn deficiency significantly enhanced shoot concentrations of iron (Fe) and manganese (Mn) for K22 by 96.2% and 34.9%, respectively, whereas it had no effects on Fe and Mn concentrations of BY815 and DAN340 (Figure 2c,d).…”

“…Evidence for identifying candidate genes by the QTLs colocalized by the loci detected in different populations have been recorded by multiple studies in maize [14,39,40]. Apart from the QTLs detected in the KB and DK populations in this study, we also used the QTLs identified in the Ye478×Wu312 (YW) RIL population to further determine the QTL colocalization among different populations [25]. Five QTL colocalization intervals were identified in eleven QTLs detected by different traits in the KB, DK, and YW RIL populations: two localizations on chromosome 1 and three localizations on chromosome 2 (Figure 7, Table 3).…”

“…The QTL qDK-ZnSc2-3, located in the interval of 157.7-173.2 Mb on chromosome 2, explained 21.2% of phenotypic variation. [25]. Candidate genes considered to be associated with Zn deficiency uptake, transport, and redistribution (ZmDMAS1, ZmTOM3, ZmNRAMP6, ZmIRT1, ZmHMA3 and ZmHMA4, ZmHMA9, and ZmVIT) are depicted in black columns.…”

“…As for maize, almost all research has paid attention to the molecular basis of biofortification for mineral elements, especially iron and zinc [22][23][24]. However, there are very few reports on mapping Zn efficiency-associated loci (ZEALs) in maize [25], which strongly hampers the development of untangling the internal mechanisms underlying the tolerance to Zn deficiency in maize.…”

“…Figure 7. Fifty-four Zn efficiency-associated loci (ZEALs) detected on chromosome 1, 2, 3, 5, 6, 7, 9, 10 in the K22×BY815 (KB) and DAN340×K22 (DK) RIL populations, and the QTL colocalizations identified in the Ye478×Wu312 (YW) RIL population[25]. Candidate genes considered to be associated with Zn deficiency uptake, transport, and redistribution (ZmDMAS1, ZmTOM3, ZmNRAMP6, ZmIRT1, ZmHMA3 and ZmHMA4, ZmHMA9, and ZmVIT) are depicted in black columns.In summary, the number of QTLs per trait varied from three to eight in these two RIL populations.…”