Analysis of Yellow Striped Mutants of Zea mays Reveals Novel Loci Contributing to Iron Deficiency Chlorosis

Abstract

The micronutrient iron (Fe) is essential for photosynthesis, respiration, and many other processes, but it is only sparingly soluble in aqueous solution, making adequate acquisition by plants a serious challenge. Fe is a limiting factor for plant growth on approximately 30% of the world’s arable lands. Moreover, Fe deficiency in humans is a global health issue, affecting 1.62 billion people, or about 25% of the world’s population. It is imperative that we gain a better understanding of the mechanisms that plants use to regulate iron homeostasis, since these will be important targets for future biofortification and crop improvement strategies. Grasses and non-grasses have evolved independent mechanisms for primary iron uptake from the soil. The grasses, which include most of the world’s staple grains, have evolved a distinct ‘chelation’ mechanism to acquire iron from the soil. Strong iron chelators called phytosiderophores (PSs) are synthesized by grasses and secreted into the rhizosphere where they bind and solubilize Fe(III). The Fe(III)-PS complex is then taken up into root cells via transporters specific for the Fe(III)-PS complex. In this study, 31 novel, uncharacterized striped maize mutants available through the Maize Genetics Cooperation Stock Center (MGCSC) were analyzed to determine whether their mutant phenotypes are caused by decreased iron. Many of these proved to be either pale yellow or white striped mutants. Complementation tests were performed by crossing the MGCSC mutants to ys1 and ys3 reference mutants. This allowed assignment of 10 ys1 alleles and 4 ys3 alleles among the novel mutants. In addition, four ys∗ mutant lines were identified that are not allelic to either ys1 or ys3. Three of these were characterized as being non-allelic to each other and as having low iron in leaves. These represent new genes involved in iron acquisition by maize, and future cloning of these genes may reveal novel aspects of the grass iron acquisition mechanism.

FAR1-RELATED SEQUENCE (FRS) and FRS-RELATED FACTOR (FRF) Family Proteins in Arabidopsis Growth and Development

“…By contrast, in maize, the terminal inverted repeats of a putative FRS5-LIKE gene were identified as an active transposon inserted in the coding region of ZmTOM1 in a mutant allele of yellow striped 3 ( ys3 ). This suggests that the transposase activity of the core transposase domain of FRS family proteins might have been retained in maize ( Chan-Rodriguez and Walker, 2018 ).…”

Genome-wide analysis of NAAT, DMAS, TOM, and ENA gene families in maize reveals their roles in regulating iron homeostasis

“…ZmTOM1 was characterized as the causal gene for ys3 mutant [32]. We found the expression of ZmTOM1 and ZmTOM3 were signi cantly induced in Fe-de cient root, suggesting their functions of MAs secretion in root.…”

“…Interference of PS synthesis and release generates strong Fe de cient phenotypes and growth defects. Two classical maize chlorosis mutants, ys1 and ys3, are characterized by yellow stripe phenotype (yellow interveinal regions and green veins), which is result from impaired MA-Fe 3+ uptake and disrupted PS secretion, respectively [31,32]. Moreover, typical Fe de ciency has also been observed as a result of disturbed DMA/NA metabolism.…”

Evaluation of the Potential Use of a Collagen-Based Protein Hydrolysate as a Plant Multi-Stress Protectant

“…The following thermal profile was set-up: 95°C for 20 s, 40 cycle of 95°C for 3 s and 60°C for 30 s. Two housekeeping transcripts were employed, one encoding an ubiquitin-conjugating enzyme (GRMZM2G027378_T01) and the other an unknown protein (GRMZM2G047204_T01), respectively. The analysis of the expression of ZmIRT1 and ZmYS1 was carried out with primers used by Nozoye et al (2013) whilst for the expression of ZmTOM1 the primers were designed accordingly to Chan-Rodriguez and Walker (2018) . The sequences of all primers were reported in Supplementary Table 3 .…”