7 Genetics and Genomics Decipher Partner Biology in Arbuscular
Mycorrhizas
LUISA LANFRANCO
1
, GENNARO CAROTENUTO
1
, ANDREA GENRE
1
, PAOLA BONFANTE
1
CONTENTS
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
II. A New Look at the Interacting Partners: From
Two to Many . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
III. Lessons from the Genome Sequencing of AM
Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
A. The Biotrophism of AM Fungi . . . . . . . . . . . . 145
B. From Structure to Function . . . . . . . . . . . . . . . 147
IV. Molecular Tools Reveal Plant Responses to
AM Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
A. Cellular and Molecular Changes in the Host
Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
B. Mycorrhizal Omics: From Local to Systemic
Responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
V. The AM Symbiosis in the Light of Natural
Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
VI. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
I. Introduction
Arbuscular mycorrhizas (AMs) are often
defined as the most widespread plant symbiosis: 72% of vascular plants (Brundrett and
Tedersoo 2018) interact at root level with a
group of early-diverging fungi, Glomeromycotina, originating a symbiosis which is not
detectable at naked eye, but has deep consequences on a global scale, from nutrient cycles
and soil structure to plant health, photosynthesis, and productivity. In addition, several nonvascular plants, including many bryophytes,
also host Glomeromycotina in the cells of
their haploid thalli. Being able to colonize
both sporophytes and gametophytes, AM
fungi are therefore central for land plant biology, making AM symbiosis a major scientific
topic in diverse fields, from mycology to botany, microbiology, ecology, agronomy, and
bioinformatics, also involving modeling and
economics studies. For this reason it is not
surprising to obtain millions of hits when
entering the keywords arbuscular mycorrhizas
in any search engine on the World Wide Web
(December 2018). However, adding the term
Genetics strongly reduces the number of hits,
and the scientific papers that have both Genetics and AMs among their keywords are only a
few. This scenario mirrors the history of
mycorrhiza studies: while the so-called endotrophic mycorrhizas have been discovered and
then studied since the end of the nineteenth
century (Bonfante 2018), application of molecular techniques to AMs required the advent of
PCR (Mullis 1990), almost exactly 100 years
later. The first papers reporting the application
of this powerful tool to mycorrhizal research
were focused on the development of molecular
probes based on RNA ribosomal genes and
aimed at the identification of fungal symbionts
in ectomycorrhizas (White et al. 1990; Gardes
and Bruns 1993). Only later, molecular tools as
well as -omics approaches were successfully
applied to AM fungi, originating in the two
main trajectories (Ferlian et al. 2018) that still
characterize mycorrhizal studies: on the one
hand, molecular approaches have provided a
wealth of information on the ecology, distribution, and diversity of AM fungi; on the other
hand, they have represented the starting point
to decipher the molecular mechanisms underlying plant-fungal interactions.
1 Dipartimento di Scienze della Vita e Biologia dei Sistemi,
Universita ` di Torino, Torino, Italy; e-mail: luisa.lanfranco@unito.it; paola.bonfante@unito.it
Genetics and Biotechnology, 3 rd Edition
The Mycota II
J.P. Benz, K. Schipper (Eds.)
© Springer Nature Switzerland AG 2020
Mycorrhizas
LUISA LANFRANCO
1
, GENNARO CAROTENUTO
1
, ANDREA GENRE
1
, PAOLA BONFANTE
1
CONTENTS
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
II. A New Look at the Interacting Partners: From
Two to Many . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
III. Lessons from the Genome Sequencing of AM
Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
A. The Biotrophism of AM Fungi . . . . . . . . . . . . 145
B. From Structure to Function . . . . . . . . . . . . . . . 147
IV. Molecular Tools Reveal Plant Responses to
AM Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
A. Cellular and Molecular Changes in the Host
Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
B. Mycorrhizal Omics: From Local to Systemic
Responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
V. The AM Symbiosis in the Light of Natural
Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
VI. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
I. Introduction
Arbuscular mycorrhizas (AMs) are often
defined as the most widespread plant symbiosis: 72% of vascular plants (Brundrett and
Tedersoo 2018) interact at root level with a
group of early-diverging fungi, Glomeromycotina, originating a symbiosis which is not
detectable at naked eye, but has deep consequences on a global scale, from nutrient cycles
and soil structure to plant health, photosynthesis, and productivity. In addition, several nonvascular plants, including many bryophytes,
also host Glomeromycotina in the cells of
their haploid thalli. Being able to colonize
both sporophytes and gametophytes, AM
fungi are therefore central for land plant biology, making AM symbiosis a major scientific
topic in diverse fields, from mycology to botany, microbiology, ecology, agronomy, and
bioinformatics, also involving modeling and
economics studies. For this reason it is not
surprising to obtain millions of hits when
entering the keywords arbuscular mycorrhizas
in any search engine on the World Wide Web
(December 2018). However, adding the term
Genetics strongly reduces the number of hits,
and the scientific papers that have both Genetics and AMs among their keywords are only a
few. This scenario mirrors the history of
mycorrhiza studies: while the so-called endotrophic mycorrhizas have been discovered and
then studied since the end of the nineteenth
century (Bonfante 2018), application of molecular techniques to AMs required the advent of
PCR (Mullis 1990), almost exactly 100 years
later. The first papers reporting the application
of this powerful tool to mycorrhizal research
were focused on the development of molecular
probes based on RNA ribosomal genes and
aimed at the identification of fungal symbionts
in ectomycorrhizas (White et al. 1990; Gardes
and Bruns 1993). Only later, molecular tools as
well as -omics approaches were successfully
applied to AM fungi, originating in the two
main trajectories (Ferlian et al. 2018) that still
characterize mycorrhizal studies: on the one
hand, molecular approaches have provided a
wealth of information on the ecology, distribution, and diversity of AM fungi; on the other
hand, they have represented the starting point
to decipher the molecular mechanisms underlying plant-fungal interactions.
1 Dipartimento di Scienze della Vita e Biologia dei Sistemi,
Universita ` di Torino, Torino, Italy; e-mail: luisa.lanfranco@unito.it; paola.bonfante@unito.it
Genetics and Biotechnology, 3 rd Edition
The Mycota II
J.P. Benz, K. Schipper (Eds.)
© Springer Nature Switzerland AG 2020