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Autor/a:
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Díaz-Benito, Pablo; Banakar, Raviraj; Rodríguez-Menéndez, Sara; Capell Capell, Teresa; Pereiro, Rosario; Christou, Paul; Abadía Bayona, Javier; Fernández, Beatriz; Álvarez-Fernández, Ana
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Notas:
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Iron and Zn deficiencies are worldwide nutritional disorders that can be alleviated by
increasing the metal concentration of rice (Oryza sativa L.) grains via bio-fortification
approaches. The overproduction of the metal chelator nicotianamine (NA) is among
the most effective ones, but it is still unclear whether this is due to the enrichment in
NA itself and/or the concomitant enrichment in the NA derivative 20-deoxymugineic
acid (DMA). The endosperm is the most commonly consumed portion of the rice
grain and mediates the transfer of nutrients from vegetative tissues to the metal rich
embryo. The impact of contrasting levels of DMA and NA on the metal distribution in
the embryo and endosperm of rice seeds has been assessed using wild-type rice and
six different transgenic lines overexpressing nicotianamine synthase (OsNAS1) and/or
barley nicotianamine amino transferase (HvNAATb). These transgenic lines outlined
three different DMA/NA scenarios: (i) in a first scenario, an enhanced NA level (via
overexpression of OsNAS1) would not be fully depleted because of a limited capacity
to use NA for DMA synthesis (lack of -or low- expression of HvNAATb), and results in
consistent enrichments in NA, DMA, Fe and Zn in the endosperm and NA, DMA and
Fe in the embryo; (ii) in a second scenario, an enhanced NA level (via overexpression
of OsNAS1) would be depleted by an enhanced capacity to use NA for DMA synthesis
(via expression of HvNAATb), and results in enrichments only for DMA and Fe, both
in the endosperm and embryo, and (iii) in a third scenario, the lack of sufficient NA
replenishment would limit DMA synthesis, in spite of the enhanced capacity to use NA
for this purpose (via expression of HvNAATb), and results in decreases in NA, variable
changes in DMA and moderate decreases in Fe in the embryo and endosperm. Also,
quantitative LA-ICP-MS metal map images of the embryo structures show that the first
and second scenarios altered local distributions of Fe, and to a lesser extent of Zn. The
roles of DMA/NA levels in the transport of Fe and Zn within the embryo are thoroughly
discussed.
This work was supported by the grants of the Spanish Ministry of Science, Innovation and Universities (AGL2016-75226-R, BIO2014-54426-P and AGL2017-85377-R, all co-financed with FEDER), Aragón Government (Group A09_17R) and Generalitat de Catalunya (Grant 2017 SGR 828). PD-B was supported by a MINECO-FPI contract. RB was supported by a Ph.D. fellowship from the University of Lleida. SR-M was supported by a research contract from the Fundación Universidad de Oviedo (FUO-069-17). BF was supported by a MINECO research contract (RYC-2014-14985; “Ramón y Cajal Program”). |
