To deal with the iron deficiency, plants have developed two strategies, one based on the pre-reduction of iron previously to its transport (strategy I) and another based on its chelation (strategy II). The Ferric Reductase Oxidase (FRO) genes are key to the strategy I, because they encode a ferric chelate reductase enzyme which reduces Fe (III) to Fe (II). In Medicago truncatula six FRO genes were identified, however their organ-specific expression is unknown. In this work, we show that the MtFRO1 and MtFRO3 genes are expressed in root; the MtFRO2 gene is expressed in leaf, flower and pod; the MtFRO4 gene is expressed in leaf and root; the MtFRO5 gene is expressed in root, stem and leaf and the MtFRO6 gene is expressed in root, flower and pod. Additionally, Plant Growth-Promoting Rhizobacteria (PGPR) are known to favor the availability of nutrients for the plant and its absorption. Our results show that the PGPR Arthrobacter agilis UMCV2 induces the expression of MtFRO genes in different organs, having the greatest effect under iron deficiency conditions. We explain the phenomenon of MtFRO genes induction by Induced Systemic Tolerance (IST); which promotes abiotic stress resistance, triggered simultaneously with Induced Systemic Resistance (ISR) and Systemic Acquired Resistance (SAR) due to an induction of genes MtDEF2.1 (related to ISR) and MtPR1 (related to SAR) observed by A. agilis UMCV2 inoculation, having the greatest effect on iron deficiency.
Para enfrentar la deficiencia de hierro, las plantas han desarrollado dos estrategias, una basada en la reducción previa del hierro antes de su transporte (estrategia I) y otra basada en su quelación (estrategia II). Los genes “Ferric Reductase Oxidase” (FRO), son clave en la estrategia I, debido a que codifican la enzima férrico quelato reductasa que reduce Fe (III) a Fe (II). En Medicago truncatula se han identificado seis genes FRO, sin embargo, se desconoce su expresión órgano específica. En el presente trabajo, demostramos que los genes MtFRO1 y MtFRO3 se expresan en raíz; el gen MtFRO2 se expresa en hoja, flor y vaina; el gen MtFRO4 se expresa en hoja y en raíz; el gen MtFRO5 se expresa en raíz, tallo y hoja y el gen MtFRO6 se expresa en raíz, flor y vaina. Adicionalmente se sabe que las bacterias “Plant Growth-Promoting Rhizobacteria” (PGPRs) favorecen la disponibilidad de nutrientes para la planta y su absorción por parte de esta. Nuestros resultados demuestran que la bacteria PGPR Arthrobacter agilis UMCV2 induce la expresión de los genes MtFRO en los diferentes, siendo el efecto mayor en condiciones de deficiencia de hierro. Explicamos el fenómeno de inducción de los genes MtFRO mediante “Induced Systemic Tolerance” (IST); que favorece la resistencia al estrés abiótico y es desencadenada simultáneamente con “Induced Systemic Resistance” (ISR) y “Systemic Acquired Resistance” (SAR), debido a que se observó una inducción de los genes MtDEF2.1 (relacionado a ISR) y MtPR1 (relacionado a SAR) al inocular A. agilis UMCV2, siendo el efecto mayor en deficiencia de hierro.
