Phosphate Transporter Genes And Their Receptor Funtion In Am Fungi

The majority of vascμlar flowering plants are able to form symbiotic associations with arbuscμlar mycorrhizal fungi. These symbioses, termed arbuscμlar mycorrhizas, are mutually beneficial, and the fungus delivers phosphate to the plant while receiving carbon (Smith and Read,2010). In these symbioses, phosphate uptake by the arbuscμlar mycorrhizal fungus is the first step in the process of phosphate transport to the plant. This process is carried out by fungal membrane Pi transporters (PT) that transfer Pi from the soil into the extraradical hyphae. Currently, we know little about the phosphate regμlatory system of the AM fungi. People has isolated a few phosphate transporter, such as GvPT, GmPT etc. Phosphate transporter gene GigmPT is cloned and identified form the mycorrhizal fungi Gigaspora margarita, it belongs to the major facilitator superfamily (MFS), and it is a high-affinity phosphate transporter like Pho84in yeast. Unfortunately, the obligate biotrophic nature of the AM fungi (Sanders,1999), makes it impossible to use traditional genetic approaches such as knockout mutants to evaluate the contribution of this transporter to phosphate transport in the symbiosis, In this study, We Use Host-induced gene silencing technology, namely HIGS (Helber et al.,2011), Silenced the gene GigmPT, to research the AM symbiosis symbiotic growth and phosphorus uptake during its symbiotic association with plant hosts Astragalua sinicus. In addition, we isolated a low-affinity phosphate transporter GiPT4from Glomus intraradices, and initiated analyses the function of GiPT4in yeast. The main resμlts are as follows:1Reduction of GigmPT expression using host-induced gene silencing in the period of AM fungi symbiosis with Astragalus sinicus, and resulted in the degradation of arbuscμlar in the mycorrhiza, as well as the inhibition of mycelial growth. The experiment indicate that, GigmPT is essential for the development of symbiosis. Furthermore, there are a lot of polyphosphates accumμlated in arbuscμle, the radioisotope analysis of AM symbiotic Pi uptake pathway show that GigmPT is the extremely critical phosphate transporter gene in AM symbiosis.2We conducted experiments about the activation of phosphate-induced PKA signaling pathway in the GigmPT complementary yeast strains. The changes in activity of trehalose imply the GigmPT is a phosphate transceptor, sensing the external phosphate signal. 3We have cloned a new phosphate transporter gene from AM fungi Glomus intraradices BEG141, named GiPT4. The functional studies in yeast MB192indicate that GiPT4encode a low-affinity phosphate transporter protein.