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Long non-coding RNAs (lncRNAs) are RNA molecules with functions independent of any protein-coding potential. A whole transcriptome (RNA-seq) study of Arabidopsis shoots under iron sufficient and deficient conditions was carried out to determine the genes that are iron-regulated in the shoots. We identified two previously unannotated transcripts on chromosome 1 that are significantly iron-regulated. We have called this iron-regulated lncRNA, CAN OF SPINACH ( COS ). cos mutants have altered iron levels in leaves and seeds. Despite the low iron levels in the leaves, cos mutants have higher chlorophyll levels than WT plants. Moreover, cos mutants have abnormal development during iron deficiency. Roots of cos mutants are longer than those of WT plants, when grown on iron deficient medium. In addition, cos mutant plants accumulate singlet oxygen during iron deficiency. The mechanism through which COS affects iron deficiency responses is unclear, but small regions of sequence similarity to several genes involved in iron deficiency responses occur in COS , and small RNAs from these regions have been detected. We hypothesize that COS is required for normal adaptation to iron deficiency conditions. 

Yellow Stripe‐Like (YSL) proteins are a family of plant transporters that are typically involved in transition metal homeostasis. Three of the four YSL clades (I, II and IV) transport metals complexed with the non‐proteinogenic amino acid nicotianamine or its derivatives. No such capability has been shown for any member of clade III, but the link between these YSLs and metal homeostasis could be masked by functional redundancy. We studied the role of the clade III YSL protein MtSYL7 inMedicago truncatulanodules. MtYSL7, which encodes a plasma membrane‐bound protein, is mainly expressed in the pericycle and cortex cells of the root nodules. Yeast complementation assays revealed that MtSYL7 can transport short peptides.M.truncatulatransposon insertion mutants with decreased expression ofMtYSL7had lower nitrogen fixation rates and showed reduced plant growth whether grown in symbiosis with rhizobia or not. YSL7 mutants accumulated more copper and iron in the nodules, which is likely to result from the increased expression of iron uptake and delivery genes in roots. Taken together, these data suggest that MtYSL7 plays an important role in the transition metal homeostasis of nodules and symbiotic nitrogen fixation.