Auxins as Signals in Arbuscular Mycorrhiza Formation

Abstract

Plant hormones such as auxin derivatives are likely signals during the establishment of an arbuscular mycorrhizal (AM) symbiosis. Although reports on auxin levels during AM in different plant species are contradictory, the contribution of auxins to the establishment of an AM symbiosis might be an important factor especially for the development of lateral roots which are the preferred infection sites for the fungi. In addition to evidence that different auxins could be elevated after colonization with AM fungi, there are also overlapping gene expression patterns between auxin-treated and AM-inoculated roots that provide further clues on auxin-triggered colonization events. Using an auxin-inducible promoter-reporter system it was shown that the reporter was strongly induced in AM colonized roots, although co-localization with AM fungi was not observed. Our data are discussed in frame of a model together with other plant hormones which might be involved in the AM colonization processes.

Influence of Arbuscular Mycorrhizal Fungi on Rooting Ability of Auxin Treated Stem Cuttings of Dalbergia melanoxylon (Guill and Perr.)

“…In addition this also enhances changes in the release of carbohydrates to the roots and modulation of phytohormone concentration resulting in increased root system branching (Kilkenny et al, 2012;Schott et al, 2013). Apart from the application of synthetic auxin, natural plant auxin play essential role as signals during the establishment of AMF symbiosis particularly for the development of lateral roots which are the preferred infection sites for the fungi (Ludwig-Muller and Guther, 2007).…”

Auxin Perception Is Required for Arbuscule Development in Arbuscular Mycorrhizal Symbiosis

“…Auxin has also been suggested to play a role in AM symbiosis, although its exact role in this type of plant-microbe interaction remains elusive (Hause et al, 2007;Hanlon and Coenen, 2011). Although an increase in auxin content in mycorrhizal roots has been previously reported for Medicago truncatula, maize (Zea mays), and soybean (Glycine max; Ludwig-Müller et al, 1997;Kaldorf and Ludwig-Müller, 2000;Fitze et al, 2005;Ludwig-Müller and Güther, 2007), no change in auxin content in mycorrhizal roots of tobacco (Nicotiana tabacum) and leek (Allium porrum) has been observed (Torelli et al, 2000;Shaul-Keinan et al, 2002). Meixner et al (2005) found that indole-3-acetic acid (IAA) levels were higher in mycorrhizal soybean roots.…”

Functional genomics and signaling events in mycorrhizal symbiosis

“…The phytohormones are important signaling molecules known to regulate many growth and developmental process in plants (Barker & Tagu 2000;Foo, Yoneyama, et al 2013;Gutjahr 2014). In maize and M. truncatula, level of indole-3-butyric acid (IBA) get increases whereas, level of indole-3-acetic acid (IAA) remains unaltered in mycorrhizal symbiotic plant (LudwigMüller et al 1997;Ludwig-Müller & Güther 2007). In Glycine max, IAA level present in higher concentration in AM root than in control plant (Meixner et al 2005).…”

“…But, its role in AM symbiosis is unclear. Some of the nitrate transporter genes get down regulated in AM root(Ludwig-Müller & Güther 2007). The endochitnase gene family members are down…”