Hormonal responses in host plants triggered by arbuscular mycorrhizal fungi

Abstract

Plant hormones are essential factors for the development of plants. They also constitute signals for the interaction of plants with microbes, including both pathogens and symbionts. The role of different classes of hormones in symbiosis is just beginning to unravel. The major advances in our knowledge on hormones in arbuscular mycorrhiza (AM) development have come from the analysis of increasing number of mutants and transgenic plants, which are available also for mycorrhizal plants now, as well as more sensitive analytical techniques. Auxins might be necessary for root growth, while cytokinins could be involved in recognition as well as in establishment of functional mycorrhiza. Jasmonic and abscisic acids are necessary for proper arbuscule formation, but for most hormones functional analysis is missing. Here, the knowledge on possible functions of different phytohormones is summarized, some data on function as far as available, are discussed and finally some thoughts about belowground signals to aboveground tissues and their effects in relation to the possible role of hormones in the upper part of the plant are given.