Plant–Fungal Interactions in Mycorrhizas

Abstract

Mycorrhizas are widespread symbiotic associations established between the roots of the majority of land plants, and a heterogeneous group of beneficial fungi belonging to diverse fungal taxa. Their ubiquitous presence argues that they have been favoured during evolution thanks to the benefits gained by both the plant and fungal partners. Advances in deoxyribonucleic acid (DNA) technology coupled to high‐throughput sequencing have allowed the genomes of some symbionts to be studied, as well as the molecular basis of cross‐talk between plant and fungus. We are beginning to see the contributions of the partners to the functioning of mycorrhizal associations. Advanced microscopy of the living partner cells has unravelled some processes determining compatibility which are a peculiar feature of mycorrhizal interactions. Key Concepts: The term Mycorrhiza comes from two Greek words for ‘fungus’ and ‘root’ and describes root–fungus associations which may be morphologically and functionally diverse. Molecular approaches have solved questions about the identity of mycorrhizal fungi both free in the soil and root associated in symbiotic structures. Nutritional interactions among plants and fungi in the rhizosphere may be saprotrophic, pathogenic or symbiotic. Recent advances in genome sequencing of ectomycorrhizal fungi identify some basic features which are characteristic of mycorrhizal fungi, that is the absence of effectors which may elicit plant defence. Transcriptome profiles of ectomycorrhizal roots reveal differential regulation of both plant and fungus. Glomeromycota possess peculiar features (i.e. an obligate biotrophic status and multinucleated hyphae) which at the moment limit a full understanding of their biology. Many model plants are compatible hosts for arbuscular mycorrhizal fungi. The transduction signalling pathways which control arbuscular mycorrhizal establishment and legume/rhizobium nodule formation are at least partly the same. Plant cells undergo complex cellular and molecular reprogramming when they accommodate the AM fungus. The core of a functioning arbuscular mycorrhiza lies at the interface between the two partners.

Two putative-aquaporin genes are differentially expressed during arbuscular mycorrhizal symbiosis in Lotus japonicus

“…In fact, unlike previous descriptions, where the central vacuole was described as fragmented due to the presence of the fungus [53], it is now known, on the basis of electron microscopy and confocal observations, that the tonoplast follows the periarbuscular membrane, leading on one hand to an increase in the surface of the tonoplast during the arbuscule development and, on the other, to an intimate interaction between the two cell membranes [50,53-55] (Figure 9). We have speculated that LjNIP1 is involved in the maintenance of plant cell turgor via water passage within the inner membrane systems, or is directly involved in the passage of water from the fungus to the plant, a mechanism that is currently poorly understood [56].…”

“…The protein is surely associated with the nuclear membranes, a typical characteristic of the ER, but it also seemed to be dispersed in other endomembranes that could be the prosecutions of the ER (such as the Golgi apparatus) or the tonoplast, which proliferates in the colonized cells surrounding the arbuscule branches [49] and - as shown under the transmission electron microscope [50] – may adhere to the periarbuscular membrane at some points (Figure 9). A homologous aquaporin, AtNIP2;1 , has been proposed to be involved in active cell elongation in the root elongating zone, where several kinds of organelles and the cell wall components are actively synthesized through the ER [51]: the same high physiological and morphological activity is surely necessary for the dramatic changes that take place in mycorrhizal cells.…”

Comparative metatranscriptomics reveals kingdom level changes in the rhizosphere microbiome of plants

“…(Feil et al, 2005;Paulsen et al, 2005). Also, association of mycorrhizal fungi with most land plants is fundamental to acquisition of mineral nutrients such as phosphate (Bonfante, 2010). However, little is known about how these organisms interact at the community level.…”

Diversity and distribution of endophytic bacterial community in the Noni (Morinda citrifolia L.) plant

“…Microbes colonizing plant surfaces and interior areas are vital for plant health and productivity (Bonfante, 2010;Berendsen et al, 2012;Ferrara et al, 2012;Monteiro et al, 2012), but some of them could lead to disease development of plants (James and Olivares, 1998;Monteiro et al, 2012;Van Overbeek et al, 2014). Prior reports indicate that *Corresponding author.…”