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Oses Pedraza R, Torres-Díaz C, Lavin P, Retamales-Molina P, Atala C, Acuña-Rodríguez I, Molina-Montenegro MA.2018. Root fungal endophytes improve the growth of antarctic plants through an enhanced nitrogen acquisition. PeerJ Preprints6:e26774v1https://doi.org/10.7287/peerj.preprints.26774v1
Mutualistic symbiosis with fungal endophytes has been suggested as a possible mechanism for extreme environment colonization by Antarctic vascular plants. Fungal endophytes improve plant stress tolerance and performance by increasing plant hormone production and the uptake of water and nutrients. However, there are still gaps regarding the mechanisms by which these process ocurr. This work explores the role of root fungal endophytes in the production of exolytic enzymes involved in endophyte-mediated mineralization and nutrient uptake, as well as their impact on the performance of Antarctic plants. Hence, we evaluated the ability of fungal endophytes isolated from the two native Antarctic vascular plants, Colobanthus quitensis and Deschampsia antarctica, to enzymatically degrade different nutrient sources, mediate nitrogen mineralization and enhance growth of the host plant. Single-spore derived isolates were identified using molecular and morphological approaches. Penicillium chrysosgenum and Penicillium brevicompactum were identified as the dominant root endophytes in C. quitensis and D. antarctica, respectively. Root endophytes exhibited hydrolytic and oxidative enzymatic activities involved in carbohydrate or protein breakdown and phosphorus solubilization. In addition, the rates and porcentages of nitrogen mineralization, as well as the final total biomass were significantly higher in C. quitensis and D. antarctica individuals with root endophytes relative to those without endophytes. Our findings suggest that root endophytes exert a pivotal ecological role based not only on their capability to breakdown different nutrient sources but also accelerating nitrogen mineralization, improving nutrient acquisition and promoting plant growth in limited nutrient soils in Antarctic terrestrial ecosystems
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Total biomass accumulation in individuals of Colobanthus quitensis and Deschampsia antarctica with (E +) and without (E -) root fungal endophytes after nitrogen mineralization assay
Penicillium chrysosgenum and Penicillium brevicompactum were used as root fungal endophytes for C. quitensis and D. antarctica, respectively. The mean and quartile distribution of individual plants (n =7) are indicated. Asterisks denote significant differences between treatments (p < 0.05) as determined by a t-test.
Kinetic of nitrogen mineralization in soils in contact with axenic individuals of Colobanthus quitensis and Deschampsia antarctica inoculated (E+) or not inoculated (E-) with root fungal endophytes
Single plants individuals (n = 7) emerging from benomyl-treated cultures were cultured in 300 ml pots containing autoclaved antarctic soil supplemented with urea as nitrogen source. Mineralization was estimated as the percentage of N-urea transformed to N-NH4+. Asterisks denote significant mean differences between treatments.