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Mycorrhiza Aug 2016Transcriptomics and genomics data recently obtained from the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis have offered new opportunities to decipher the...
Transcriptomics and genomics data recently obtained from the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis have offered new opportunities to decipher the contribution of the fungal partner to the establishment of the symbiotic association. The large number of genes which do not show similarity to known proteins witnesses the uniqueness of this group of plant-associated fungi. In this work, we characterize a gene that was called RiPEIP1 (Preferentially Expressed In Planta). Its expression is strongly induced in the intraradical phase, including arbuscules, and follows the expression profile of the Medicago truncatula phosphate transporter MtPT4, a molecular marker of a functional symbiosis. Indeed, mtpt4 mutant plants, which exhibit low mycorrhizal colonization and an accelerated arbuscule turnover, also show a reduced RiPEIP1 mRNA abundance. To further characterize RiPEIP1, in the absence of genetic transformation protocols for AM fungi, we took advantage of two different fungal heterologous systems. When expressed as a GFP fusion in yeast cells, RiPEIP1 localizes in the endomembrane system, in particular to the endoplasmic reticulum, which is consistent with the in silico prediction of four transmembrane domains. We then generated RiPEIP1-expressing strains of the fungus Oidiodendron maius, ericoid endomycorrhizal fungus for which transformation protocols are available. Roots of Vaccinium myrtillus colonized by RiPEIP1-expressing transgenic strains showed a higher mycorrhization level compared to roots colonized by the O. maius wild-type strain, suggesting that RiPEIP1 may regulate the root colonization process.
Topics: Fungal Proteins; Gene Expression Regulation, Fungal; Glomeromycota; Green Fluorescent Proteins; Medicago truncatula; Mycorrhizae; Plant Roots; Yeasts
PubMed: 27075897
DOI: 10.1007/s00572-016-0697-0 -
The Biochemical Journal 1948
PubMed: 16748446
DOI: 10.1042/bj0430528 -
The New Phytologist Jan 1997Production of enzymes which degrade plant cell wall macromoleculea has been studied in relatively few ericoid fungal isolates, although these polymers arc a major...
Production of enzymes which degrade plant cell wall macromoleculea has been studied in relatively few ericoid fungal isolates, although these polymers arc a major component of the organic litter and an important source of nutrients for these fungi. Our aims were to investigate whether the ability to degrade the wall pectic component, only reported for one isolate, is a general feature of ericoid fungi. Of about 35 isolates from different geographic regions, all were capable of growing on pectin as the sole carbon source. Polygalacturonase (PG) activity was detected to a different degree in the culture filtrates and independently of the fungal growth rate. Solid and liquid isoelectric focusing allowed separation and identification of several polygalacturonase isoforms. Among the fungal isolates investigated, those from the northern hemisphere produced mostly acidic isoforms, whereas isolates from South Africa secreted more abundantly basic isoforms. However, purification and biochemical characterization of several PG isoforms from the different isolates revealed an optimal activity in the acidic pH range for all the PG enzymes tested. Polygalacturonase enzymes seem to be an important component of the enzymatic arsenal secreted by ericoid fungi during their saprotrophic life. In addition, they could also play a role during root colonization, since penetration across the plant cell wall is a prerequisite for the establishment of endomycorrhizal symbiosis.
PubMed: 33863151
DOI: 10.1046/j.1469-8137.1997.00627.x