Identification of putative target genes to manipulate Fe and Zn concentrations in rice grains.

Rice is the staple food of half of the world's population; however, it is a poor source of essential micronutrients such as Fe and Zn. Since flag leaves are one of the sources of remobilized metals for developing seeds, the identification of the molecular players that might contribute to the process of metal transport from flag leaves to the seeds may be useful for biofortification purposes. We analyzed the expression of 25 metal-related genes from rice, including rice homologues for YSLs, NRAMPs, ZIPs, IRT1, VIT1 (coding for known or potential metal transporters), as well as NASs, FROs and NAC5 (involved in metal homeostasis) in flag leaves of eight rice cultivars (showing contrasting levels of seed Fe and Zn) during panicle emergence (R3) and grain filling stage (R5). The expression level of nine of these genes (OsYSL6, OsYSL8, OsYSL14, OsNRAMP1, OsNRAMP7, OsNRAMP8, OsNAS1, OsFRO1 and OsNAC5) in flag leaves exhibited significant correlations with Fe and/or Zn concentrations in the seeds. In this way, our study has provided a short list of putative target genes to manipulate Fe and Zn concentrations in rice grains.