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Martinez-Cuenca M.-R.,Instituto Valenciano Investigaciones Agrarias | Legaz F.,Instituto Valenciano Investigaciones Agrarias | Forner-Giner M.T.,Instituto Valenciano Investigaciones Agrarias | Primo-Millo E.,Instituto Valenciano Investigaciones Agrarias | Iglesias D.J.,Instituto Valenciano Investigaciones Agrarias
Journal of Plant Physiology | Year: 2013

The effect of bicarbonate ion (HCO3 -) on the mobilization of iron (Fe) reserves from cotyledons to roots during early growth of citrus seedlings and its influence on the components of the iron acquisition system were studied. Monoembryonic seeds of Citrus limon (L.) were germinated " in vitro" on two iron-deprived media, supplemented or not with 10mM HCO3 - (-Fe+Bic and -Fe, respectively). After 21d of culture, Fe concentration in seedling organs was measured, as well as gene expression and enzymatic activities. Finally, the effect of Fe resupply on the above responses was tested in the presence and absence of HCO3 - (+Fe+Bic or +Fe, respectively). -Fe+Bic seedlings exhibited lower Fe concentration in shoots and roots than -Fe ones but higher in cotyledons, associated to a significative inhibition of NRAMP3 expression. HCO3 - upregulated Strategy I related genes (FRO1, FRO2, HA1 and IRT1) and FC-R and H+-ATPase activities in roots of Fe-starved seedlings. PEPC1 expression and PEPCase activity were also increased. When -Fe+Bic pre-treated seedlings were transferred to Fe-containing media for 15d, Fe content in shoots and roots increased, although to a lower extent in the +Fe+Bic medium. Consequently, the above-described root responses became markedly repressed, however, this effect was less pronounced in +Fe+Bic seedlings. In conclusion, it appears that HCO3 - prevents Fe translocation from cotyledons to shoot and root, therefore reducing their Fe levels. This triggers Fe-stress responses in the root, enhancing the expression of genes related with Fe uptake and the corresponding enzymatic activities. © 2013 Elsevier GmbH.


Martinez-Cuenca M.-R.,Instituto Valenciano Investigaciones Agrarias | Iglesias D.J.,Instituto Valenciano Investigaciones Agrarias | Forner-Giner M.A.,Instituto Valenciano Investigaciones Agrarias | Primo-Millo E.,Instituto Valenciano Investigaciones Agrarias | Legaz F.,Instituto Valenciano Investigaciones Agrarias
Acta Physiologiae Plantarum | Year: 2013

This work studies the effect of bicarbonate on plant performance and the iron acquisition system of Forner-Alcaide 5 (FA-5) seedlings, a citrus genotype known for its tolerance to calcareous soils. Plants were irrigated for 6 weeks with or without 10 mM NaHCO3. Treatment significantly decreased shoot growth, photosynthetic levels and iron concentration in shoots and roots. o,o-57FeEDDHA experiments indicated that 57Fe uptake by roots was inhibited in treated plants. Moreover, those seedlings accumulated more 57Fe in roots, and enhanced mRNA accumulation of ferric reductase genes FRO1 and FRO2 and FC-R activity in roots. H+-ATPase activity and HA1 gene expression were also increased, while HA2 was not affected. In addition, expression of the iron transporter gene IRT1 was increased, while IRT2 was not significantly affected. Finally, according to PEPC enzymatic activity, PEPC1 gene expression was higher in treated roots. In conclusion, it appears that bicarbonate prevents medium acidification by roots, thus reducing Fe2+ uptake. Accordingly, Fe deficiency enhanced the expression of some genes related with the Fe acquisition system (IRT1, FRO1, FRO2, HA1 and PEPC1) and the activity of the corresponding enzymes, which appear to constitute an adaptive mechanism of FA-5 in these soils. © 2013 Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków.

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