Host‐ and stage‐dependent secretome of the arbuscular mycorrhizal fungus Rhizophagus irregularis

Abstract

Arbuscular mycorrhizal fungi form the most wide-spread endosymbiosis with plants. There is very little host specificity in this interaction, however host preferences as well as varying symbiotic efficiencies have been observed. We hypothesize that secreted proteins (SPs) may act as fungal effectors to control symbiotic efficiency in a host-dependent manner. Therefore, we studied whether arbuscular mycorrhizal (AM) fungi adjust their secretome in a host- and stage-dependent manner to contribute to their extremely wide host range. We investigated the expression of SP-encoding genes of Rhizophagus irregularis in three evolutionary distantly related plant species, Medicago truncatula, Nicotiana benthamiana and Allium schoenoprasum. In addition we used laser microdissection in combination with RNA-seq to study SP expression at different stages of the interaction in Medicago. Our data indicate that most expressed SPs show roughly equal expression levels in the interaction with all three host plants. In addition, a subset shows significant differential expression depending on the host plant. Furthermore, SP expression is controlled locally in the hyphal network in response to host-dependent cues. Overall, this study presents a comprehensive analysis of the R. irregularis secretome, which now offers a solid basis to direct functional studies on the role of fungal SPs in AM symbiosis.

A Medicago truncatula SWEET transporter implicated in arbuscule maintenance during arbuscular mycorrhizal symbiosis

“…To identify which SWEET genes may be involved in AM symbiosis, we determined the expression patterns of all SWEET genes in M. truncatula roots inoculated with the AM fungus R. irregularis. First, we analysed RNA-seq transcriptome data of cortical cells containing arbuscules and cortical cells adjacent to hyphae, which were isolated by laser microdissection (Zeng et al, 2018). This analysis showed that of all the SWEET genes, only MtSWEET1b (Medtr3g089125) has high expression in root cells that are in contact with the fungus (Fig.…”

“…The parameters used for mapping and TPM (transcripts per million; Wagner et al ., ) calculation are described in Zeng et al . ().…”

“…The raw RNA-sequencing data of cortical cells containing arbuscules and cortical cells adjacent to hyphae were obtained by Zeng et al (2018). All the clean reads were mapped to the M. truncatula genome version MT4.0 (Tang et al, 2014) using CLC GENOMICS WORKBENCH 10.0.1 (Qiagen).…”

“…All the clean reads were mapped to the M. truncatula genome version MT4.0 (Tang et al, 2014) using CLC GENOMICS WORKBENCH 10.0.1 (Qiagen). The parameters used for mapping and TPM (transcripts per million; Wagner et al, 2012) calculation are described in Zeng et al (2018).…”

A lysin motif effector subverts chitin‐triggered immunity to facilitate arbuscular mycorrhizal symbiosis

“…RNA sequencing (RNAseq) data were collected from the following databases: NCBI gene expression omnibus http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE99655 for data from Medicago , chives, and Nicotiana benthamiana as well as laser microdissected ARBs and IRM; extraradical mycelium (ERM) and germinating spores from DDBJ database DRA002591; Lotus japonicus and tomato from DDBJ database DRA005187. RNAseq data were analysed as described by Zeng et al (). Quantification was done using default setting in CLC G enomics W orkbench 10.0.1.…”