Mapping and Characterization of the Gene That Controls Iron Uptake in Melon ( L.).

Iron (Fe) deficiency in plants limits crop growth and productivity. Molecular mechanisms that plants use to sense and respond to Fe deficiency by coordinated expression of Fe-uptake genes are not fully understood. The C940-fe chlorotic melon () mutant known as is unable to upregulate Fe-uptake genes, however, the gene had not been identified. In this study, we used two F mapping populations to map and identify the gene as , a homolog of subgroup Ib genes from that are involved in transcriptional regulation of Fe-uptake genes in partnership with the gene. A Ty1-copia type retrotransposon insertion of 5.056 kb within is responsible for the defect in in , based on sequencing and expression analysis. This retrotransposon insertion results in multiple non-functional transcripts expected to result in an altered and truncated protein sequence. Hairy root transformation of plants using wild-type resulted in functional complementation of the chlorotic phenotype. Using a yeast-2-hybrid assay, the transcription factor Fit interacted with the wild-type bHLH38 protein, but did not interact with the bHLH38 protein, suggesting that heterodimer formation of Fit/bHLH38 to regulate Fe-uptake genes does not occur in roots. The second subgroup Ib gene in the melon genome is not functionally redundant to , in contrast to Arabidopsis where four subgroup Ib genes are functionally redundant. Whereas the Arabidopsis transcript levels are upregulated by Fe deficiency, melon was not regulated at the transcript level. Thus, the mutant may provide a platform for studying genes and proteins from other plant species.