Signalling and Communication in the Actinorhizal Symbiosis

Abstract More than 200 species of non-legume dicotyledonous plants, mostly trees and shrubs, belonging to eight different families and 24 genera can enter actinorhizal symbioses with the nitrogen-fixing actinomycete Frankia. Actinorhizal nodules consist of multiple lobes, each of which displays a lateral root structure with infected cells in the expanded cortex. Whereas the key molecules involved in the molecular dialogue between the symbiotic partners have not yet been characterized, the...

Other Characteristics

In addition to the more obvious hormogonia traits of motility, chemotaxis and plant recognition adhesion, there is evidence that more subtle aspects of their behaviour are also crucial for successful plant infection. For example, in N. punctiforme inactivation of the gene sigH, which encodes an alternative sigma subunit of RNA polymerase, and transcription of which is induced by HIF (Meeks 2003), has no effect on the frequency of HIF-induced hormogonia, yet the hormogonia are fivefold more...

The SYM Pathway

Most - although not all - of the responses described so far are in fact mediated by the activity of a few known gene products (Kistner et al. 2005). These are expressed in all AM host plants and are known as the common SYM genes (Oldroyd and Downie 2006), with reference to the dual role they have in legumes, in controlling both AM symbiosis and nitrogen-fixing nodulation (Parniske 2008). While, anyway, a few more genes have been identified in nodulation-specific branches of this pathway,...

RKN Infection and Giant Cell Ontogenesis

In contrast to rhizobia which interact with legume species, the RKN host range encompasses nearly all flowering plants, leading to extensive crop loss (Abad and Williamson 2010). The wide host range (thousand of plant species) is associated with a worldwide distribution in all temperate and tropical areas making them extremely successful and damaging parasites (Trudgill and Blok 2001). RKN infect roots as microscopic vermiform second-stage juveniles (J2). Mobile J2s penetrate the root usually...

Plant Hormone Response

Since plant organogenesis is largely regulated by plant hormones, researches have focused on whether microorganisms directly or indirectly manipulate the plant hormone balance to induce root nodule or gall formation. Using an auxin-responsive promoter GH3 (or its synthetic derivative DR5) fused to the reporter gene GUS, an early and transient increase in auxin response was detected in giant cells and in white clover nodule primordia (Mathesius et al. 1998 Hutangura et al. 1999). Nodule...

Alternative Infection Mechanisms Single Cell Peg Entry

Characterisation of synthetic mutants combining gain of function (snf1) and loss of function mutations lead to a remarkable and unexpected discovery of an infection thread independent single cell entry mechanism in L. japonicus (Madsen et al. 2010). This intracellular infection of individual host cells by a process best described as peg entry may constitute the ground state of bacterial invasion during evolution of nodulation, and may allow for an analysis of the cardinal requirements...

Biological Activity

Two distinct roles for flavonoids and their related molecules have been suggested in the context of early communication during the legume-Rhizobium symbiosis (1) they are involved in chemotaxis responses of rhizobia (2) they modulate nod gene expression of rhizobia (Shaw et al. 2006). It is essential that rhizobia present in the rhizosphere are attracted to host roots in order for the symbiosis to be formed. Plant roots secrete many compounds into the rhizosphere and in doing so modulate...

Angiosperms Gunnera

This is the only intracellular cyanobacterial-plant symbiosis (the Nostoc cells are found between the host cell wall and the plasmalemma) and the only symbiosis with a flowering plant (Bergman 2002 Bergman and Osborne 2002 Bergman et al. 2007a). The genus Gunnera consists of plants with leaves varying from 1 cm to several metres across (Fig. 5a), once found only in warm, wet equatorial regions, but which now commonly occur in suitably wet temperate regions (Osborne and Sprent 2002). The...

Info

E values for this analysis and the amino acid sequence identity between the M. grisea protein and the predicted polypeptide sequence for the E.festucae homologue are given. Proteins chosen for this analysis were based on the MAP kinase pathway schemes presented in Dean et al. (2005) and Rispail et al. (2009). E.festucae gene models are available on requestaWhere the E.festucae genes are named differently to their S. cerevisiae homologues, the S. cerevisiae names are also given E values for this...

Ustilago maydis as a Model System for Biotrophic Fungi

U. maydis is the leading model organism of the plant pathogenic smut fungi. The basidiomycete fungus parasitizes only on Zea mays and its wild progenitor teosinte (Z. mays ssp. mexicana and ssp. pavigluminis) where it causes corn smut disease. Concomitantly, U. maydis induces the formation of plant tumors in which the fungus completes its disease cycle (Christensen 1963 Banuett 1995 Banuett and Herskowitz 1996 Doehlemann et al. 2008a). U. maydis has a diphasic life cycle the fungus grows...

Biotrophic Lifestyle

Both N. lolii and E. festucae form stable, asymptomatic mutualistic associations with L. perenne and are vertically transmitted through the seed following colonisation of the ovule (Philipson and Christey 1986). After fertilisation, the endophyte colonises the embryo sac and as the seed matures hyphae spreads throughout the embryo (Philipson and Christey 1986 May et al. 2008). During seed germination, hyphae colonise the shoot apical meristem (SAM) from where they enter leaf primordia and...

Definition of Biotrophic Plant Parasite Interactions

One way to classify plant pathogens is according to their feeding strategy (Oliver and Ipcho 2004). By definition biotrophic plant parasites rely on living substrates. Many of them establish long-term feeding relationships with their hosts (Lewis 1973 Staples 2000 Mendgen and Hahn 2002). These characteristics are also resembled by the term biotrophy that has been derived from the Greek words bios (life) and trophy (feeding). In contrast to biotrophs, necrotrophic pathogens (e.g., Sclerotina...

Signalling Associated with Synthesis of Bioprotective Metabolites

Four main classes of biologically active metabolites have been identified in grass hosts infected with E. festucae peramine, indole diterpenes (principally lolitrem B), ergot alkaloids (principally ergovaline) and lolines. Peramine is a potent feeding deterrent of adult Argentine stem weevil (ASW Listronotus bonariensis), an economically important pest of L. perenne in New Zealand agricultural ecosystems. Lolitrem B also has biological activity against some insect larvae but is better known as...

Structure and Development of Ectomycorrhizae

Endofitos And Ppt

While only around 3 of seed-bearing plants establish an ectomycorrhizal (ECM) symbiosis with fungi, ECMs are the most common form of symbiosis for the majority of boreal and temperate forest trees. The fungal community involved in UMR 1136 Interactions Arbres Micro-organismes, Centre INRA de Nancy, 54280 Champenoux, France Department of Forest Genetics and Plant Physiology, Umea Plant Science Centre, Swedish University of Agricultural Sciences, 90 187 Ume , Sweden UMR 1136 Interactions Arbres...

Invasion Through Root Hair Infection Threads

In L. japonicus the normal infection occurs through infection threads initiated in elongating root hairs of the susceptible region located just behind the root tip. Upon formation of infection pockets, the root hair cell wall dissolves and an infection thread is initiated by invagination and subsequent polar extension of the plasma membrane, which is accompanied by the deposition of new cell wall material (see Gage (2004) for a review). Inward growing infection threads progress through the root...

Gymnosperms Cycads

Amfigastri Polytrichum

Cycads are evergreen palm-like plants, from 10 cm to 20 m in height, which once dominated the Earth's forests but are now restricted to subtropical and tropical regions of mostly the southern hemisphere (Brenner et al. 2003 Vessey et al. 2005). Cycads produce coralloid (coral-like) roots (Fig. 4a) that become infected with heterocystous cyanobacteria (Costa and Lindblad 2002 Lindblad and Costa 2002 Vessey et al. 2005 Lindblad 2009) usually from the genus Nostoc, although Fig. 2 The liverwort...

Structure and Function of Fungal and Oomycete Haustoria

Haustoria Formed Fungi

Haustoria formed by biotrophic or hemibiotrophic rusts, powdery mildews and oomycetes are central to the development of a stable biotrophic relationship between pathogen and plant and are key sites for the absorption of the plant nutrients that are essential for pathogen growth, development and reproduction. For their function, haustoria depend on highly regulated molecular exchange across the haustorium-plant boundary. Before nutrients begin to move from plant to pathogen across this...

Magnaporthe oryzae

Magnaporthe Oryzae

Magnaporthe oryzae is best known for the devastating blast disease it causes on rice leaves Talbot 2003 but it is also able to infect the roots of rice plants Sesma and Osbourn 2004 Marcel et al. 2010 Tucker et al. 2010 . Depending on the host, symptoms of M. oryzae infection can range from no visible symptoms to larger necrotic lesions of different sizes indicating different proportions of necrotrophic and biotrophic growth in fungal infection Heath et al. 1991 . Tissue-specific differences in...

Colletotrichum Species

Colletotrichum Structure

Most species of Colletotrichum are hemibiotrophs that grow biotrophically in living plant cells for 1 to a few days before adopting a necrotrophic life-style. Like the powdery mildews and M. oryzae, most Colletotrichum species penetrate the host cuticle and cell wall of epidermal cells directly, rather than entering through a stomatal aperture Fig. 4 Willmer and Fricker 1996 Mendgen and Deising 1993 . Colletotrichum conidia germinate on the surface of a host and form a short germ tube which...

Katharina Markmann Simona Radutoiu and Jens Stougaard

Abstract Like the two important crop legumes soybean and common bean, the model legume Lotus japonicus develops determinate root nodules. L. japonicus is normally infected through root hair infection threads in a process closely synchronised with the progressing primordial cell divisions and organ development. Recent studies of symbiotic mutants have however led to a remarkable and unexpected discovery of two alternative intercellular infection modes, crack entry and infection thread...

The Cyanobacteria Plant Symbioses

Cavicularia Images

This chapter deals with the endophytic cyanobacteria-plant symbioses in which the cyanobiont is located within the host tissue or, in the case of the angiosperm Gunnera, within the host cells. However, many cyanobacteria, including nitrogen-fixing strains, grow as epiphytes on a wide range of plants, particularly in aquatic environments Adams 2011 . These loose associations won't be discussed here, as they are poorly studied and little is known about the extent to which the plant benefits,...

Delivery of Effectors into Host Cells

While many of the fungal and oomycete effectors discussed in the previous section are likely to function in the plant apoplast, the direct interaction between Avr proteins and their cognate resistance proteins known to occur within the plant cytoplasm suggests that pathogen effectors must also function in the host cytoplasm. Early evidence for delivery of fungal proteins into host plant cells came from immunolocalisation of UfRTPl, a haustorially expressed glycoprotein of unknown function...