GSE67906
Gigaspora rosea gene regulation in early steps of AMF-plant symbiosis
Purpose: we here adress the gene regulation of G.rosea in response to plant signals in the switch from asymbiotic to presymbiotic growth. Methods:  -Strigolactone response: Spores of G.rosea were treated with GR24 (a synthetic strigolactone analog) and collected at 2 days after treatment. Control conditions: spores treated with solvent (M medium acetone 0.1%. Assay and control were performed in triplicates. -Root exsudate response: a cellophane membrane allowing molecule exchanges was deposited on in vitro Daucus carotta roots. Spores were spotted on this membrane and collected 10 days later. Control conditions: spores were spotted on cellophane membrane directly deposited on solid M medium. Assay and control were performed in triplicates. -Fungal gene expression were analyzed on mRNA were sequenced by Illumina HiSeq. sequencing Reads were firstly used in the de novo assembly of Gigaspora rosea Non Redundent Virtual Transcript and then mapped on the assembled transcriptome using CLC genomics workbench. Results: while GR24 triggered the regulation of only few genes which includes 32 genes upregulated (fold chang >2; FDR<0,05, experiment difference>10) and 61 downregulated (fold change < -2; FDR<0,05,experiment difference>10) genes, root exudates regulated several times more genes. A total of 390 genes were up-regulated by root exudates and 442 genes were down-regulated. Moreover, a majority of the genes (23 of 32 upregulated and 25 of 61 downregulated genes) regulated by GR24 were also regulated by root exudates. This is in consistant with the fact that strigolactones secreted from plant root are already characterized as a group of plant signals during AM symbiosis. The result that a large part of genes were differentialy expressed in reponse to root exudates but not GR24 suggested the presence of other plant signals than strigolactones. Conclusions: as a key player during the switch from asymbiotic to presymbiotic growth of G.rosea, plant root secreted signals - including but not limited to striglactones - significantly modified the expression of many G.rosea genes. The genes differentially expressed are mainly involved in oxidation-redution and metabolic processes that might contribute to prepare G.rosea for the following steps of symbiotic association with the host plant. Overall design: mRNA profiles spores treated with strigolactone or root exudates were generated by deep sequencing, in triplicate, using Illumina.