Revisiting Fe/S interplay in tomato: A split-root approach to study the systemic and local responses

Although S was freely available to half root system and thus plant S status was preserved, S-deficient part of root apparatus exhibited a decrease of total S, thiols and protein content, an enhanced activity of both ATPsulfurylase and O-acetylserine(thiol)lyase, and a higher expression of SlST1.1, as occurring under S deficiency. The side of the root apparatus exposed to combined S and Fe deficiency, showed an over induction of the FeIII-reducing capacity (+40%) and of the expression levels of the gene codifying for this protein (SlFRO1), with respect to the Fe-deficient part of the root system. Interestingly, the regulation pattern of the bHLH transcription factor SlFER, controlling the expression of both SlFRO1 and SlIRT1 genes, was very close to that of SlFRO1. SlIRT1 expression levels appeared unaffected by S supply, suggesting distinct regulatory processes targeting SlFRO1 and SlIRT1.