Abstract
The present study highlights the molecular regulation of iron transport in soyFER1-overexpressing transgenic rice. Accumulation of iron in three different seed developmental stages, milk, dough, and mature, has been examined. The transgenic seeds of the milk stage showed significant augmentation of iron and zinc levels compared with wild-type seeds, and similar results were observed throughout the dough and mature stages. To investigate the regulation of iron transport, the role of miRNAs was studied in roots of transgenic rice. Sequencing of small RNA libraries revealed 153 known and 41 novel miRNAs in roots. Among them, 59 known and 14 novel miRNAs were found to be significantly expressed. miR166, miR399, and miR408 were identified as playing a vital role in iron uptake in roots of transgenic plants . Most importantly, four putative novel miRNAs, namely miR11, miR26, miR30, and miR31, were found to be down-regulated in roots of transgenic plants. For all these four novel miRNAs, natural resistance-associated macrophage protein 4 (NRAMP4), encoding a metal transporter, was predicted as a target gene. It is hypothesized that the NRAMP4 transporter is activated in roots of transgenic plants due to the lower abundance of its corresponding putative novel miRNAs. The relative transcript level of the NRAMP4 transcript was increased from 0.107 in the wild type to 65.24 and 55.39 in transgenic plants, which demonstrates the elevated amount of iron transport in transgenic plants. In addition, up-regulation of OsYSL15, OsFRO2, and OsIRT1 in roots also facilitates iron loading in transgenic seeds.
Highlights
Iron is an essential mineral nutrient required for human physiology
Endosperm-specific overexpression of various transporters and enzymes involved in phytosiderophore biosynthesis such as ferric chelate reductase oxidase 2 (FRO2), iron-related transporter 1 (IRT1), yellow stripe-like (YSL) family members, NAS, and NAAT has increased iron in milled rice grain by 3- to 4-fold (Wang et al, 2013)
To identify the most important stage of iron and zinc transport during grain maturation, roots, flag leaves, and immature or mature seeds of WT and transgenic ferritin-overexpressing plant (TF) plants collected during three different grain maturation stages, namely milk, dough, and mature stages, and concentrations of iron and zinc were analysed
Summary
Iron is an essential mineral nutrient required for human physiology. A low intake of iron through food or low iron bioavailability causes nutrient disorders such as iron deficiency anaemia (IDA) which is commonly observed in the Indian population consuming rice as a major food (Stein et al, 2008). Endosperm-specific overexpression of various transporters and enzymes involved in phytosiderophore biosynthesis such as ferric chelate reductase oxidase 2 (FRO2), iron-related transporter 1 (IRT1), yellow stripe-like (YSL) family members, NAS, and NAAT has increased iron in milled rice grain by 3- to 4-fold (Wang et al, 2013). Tissuespecific overexpression of rice endogenous ferritin (OsFER2) or soybean ferritin (soyFER1) has been shown to increase iron in the endosperm (milled rice) by 2.54- and 2.09-fold, Abbreviations: DMA, deoxymugineic acid; EBR, epibrassinolide; FRO, ferric chelate reductase oxidase; GO, Gene Ontology; HMA, 3-hydroxymugineic acid; IDA, iron deficiency anaemia; IRT, iron-regulated transporter, MA, mugineic acid; NGS, next-generation sequencing; NRAMP; natural resistance-associated macrophage protein; SAM, S-adenosylmethionine; TIGR, The Institute for Genome Research; TF, transgenic ferritin-overexpressing plant; WT, wild type; YSL, yellow stripe like. Overexpression of ferritin in rice endosperm activates several iron transporters which facilitates iron and zinc loading in rice endosperm (Paul et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
