Transcriptional response of <em>Medicago truncatula</em> sulphate transporters to arbuscular mycorrhizal symbiosis with and without sulphur stress

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Inglés. Sulphur is an essential macronutrient for plantgrowth, development and response to various abiotic andbiotic stresses due to its key role in the biosynthesis ofmany S-containing compounds. Sulphate represents a verysmall portion of soil S pull and it is the only form that plantroots can uptake and mobilize through H?-dependentco-transport processes implying sulphate transporters.Unlike the other organically bound forms of S, sulphate isnormally leached from soils due to its solubility in water,thus reducing its availability to plants. Although ourknowledge of plant sulphate transporters has been growingsignificantly in the past decades, little is still known aboutthe effect of the arbuscular mycorrhiza interaction on sulphuruptake. Carbon, nitrogen and sulphur measurementsin plant parts and expression analysis of genes encodingputative Medicago sulphate transporters (MtSULTRs) wereperformed to better understand the beneficial effects ofmycorrhizal interaction on Medicago truncatula plantscolonized by Glomus intraradices at different sulphateconcentrations. Mycorrhization significantly promotedplant growth and sulphur content, suggesting increasedsulphate absorption. In silico analyses allowed identifyingeight putative MtSULTRs phylogenetically distributedover the four sulphate transporter groups. Some putativeMtSULTRs were transcribed differentially in roots andleaves and affected by sulphate concentration, while otherswere more constitutively transcribed. Mycorrhizal-inducibleand -repressed MtSULTRs transcripts were identifiedallowing to shed light on the role of mycorrhizal interactionin sulphate uptake.