PAP-SAL1 chloroplast retrograde pathway modulates iron deficiency response in alkaline soils

GOMEZ-CASATI, DIEGO F.; PAGANI, MARIA A.; BALPARDA, MANUEL

Paraná

Congreso; LIV Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular; 2018

Iron (Fe) is an essential micronutrient for plants and is present abundantly in the Earth´s crust. However, its bioavailability in most soils is low, due to their alkaline pH that lowers the solubility of the metal. In previous communications, we have demonstrated the existence of a link between the organelle-nucleus retrograde signaling PAP-SAL1 pathway, which senses the internal Fe deficiency, and the iron uptake activity in roots. One of the objectives of this study was to characterize mutant plants in this signaling pathway with respect to their growth in alkaline soils. We measured phenotypic characteristics such as rosette area and chlorophyll content, and we observed that mutants lines presented an increment in both compared to wild-type plants. Likewise, we studied genes implicated in the biosynthesis of secondary metabolites derived from phenylpropanoids, which, excreted to the rhizosphere, improve Fe availability, in two different pH conditions: 5.7 (control) and 7.5 (alkaline). The relative expressions of these genes were elevated in mutant lines compared with wild-type seedlings in both pH conditions. Finally, we quantified the phenolic compounds excreted to the rhizosphere. Results show an increase in these metabolites in the culture medium in mutant lines compared to wild-type plants. In summary, PAP-SAL1 mutants show alterations in the biosynthesis of Fe-mobilizing metabolites that improve their growth in alkaline soils. As we have mentioned previously, our results suggest that the PAP-SAL1 retrograde pathway has a connection with Fe deficiency sensing in Arabidopsis thaliana.