Fungal Endophytes Enhance the Photoprotective Mechanisms and Photochemical Efficiency in the Antarctic Colobanthus quitensis (Kunth) Bartl. Exposed to UV-B Radiation

Abstract

Antarctic plants have developed mechanisms to deal with one or more adverse factors which allow them to successfully survive such extreme environment. Certain effective mechanisms to face adverse stress factors can arise from the establishment of functional symbiosis with endophytic fungi. In this work, we explored the role of fungal endophytes on host plant performance under high level of UV-B radiation, a harmful factor known to damage structure and function of cell components. In order to unveil the underlying mechanisms, we characterized the expression of genes associated to UV-B photoreception, accumulation of key flavonoids, and physiological responses of Colobanthus quitensis plants with (E+) and without (E−) fungal endophytes, under contrasting levels of UV-B radiation. The deduced proteins of CqUVR8, CqHY5, and CqFLS share the characteristic domains and display high degrees of similarity with other corresponding proteins in plants. Endophyte symbiotic plants showed lower lipid peroxidation and higher photosynthesis efficiency under high UV-B radiation. In comparison with E−, E+ plants showed lower CqUVR8, CqHY5, and CqFLS transcript levels. The content of quercetin, a ROS-scavenger flavonoid, in leaves of E-plants exposed to high UV-B was almost 8-fold higher than that in E+ plants 48 h after treatment. Our results suggest that endophyte fungi minimize cell damage and boost physiological performance in the Antarctic plants increasing the tolerance to UV-B radiation. Fungal endophytes appear as fundamental biological partners for plants to cope with the highly damaging UV-B radiation of Antarctica.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020

“…The equivalent protection response of the vascular plant, Colobanthus quitensis , to UV radiation is enhanced by forming mutually beneficial relationships between plant roots and soil fungi (i.e., mycorrhizae). These associations rely on a stable ecosystem and support the plant’s floral development and growth, also reducing oxidative stress and membrane damage, protecting photosynthesis and maintaining photoprotection through UV-screening flavonoids [ 142 – 144 ]. In the native Antarctic grass, Deschampsia antarctica , a key enzyme in the synthesis of flavonoids (chalcone synthase) matches that present in temperate grasses, including the cereal grains rice and barley [ 145 ], indicating a common regulatory role in UV-photoprotection across these species.…”

Biological Soil Crusts as Ecosystem Engineers in Antarctic Ecosystem

“…Due to variability in terms of BSCs microorganism composition, the following analyses were conducted using a BSC collected from site 3 (BSC-3) ( Figure 1C ), as it showed a higher relative proportion of Cyanobacteria compared with BSC-1 and BSC-2. Hence, to evaluate the effect of BSC-3 crust samples on soil properties, we prepared twenty 250-ml pots (16 × 13 cm), which were filled with a mixture of sterile sand, native soil, and peat in a 4:4:1 proportion, that has been used on previous studies involving Antarctic vascular plants ( Barrera et al, 2020 ). In half of the pots ( N = 10), we randomly placed four 1-cm 2 BSC-3 fragments per pot soil surface, equidistantly from each other, in a cross-shaped fashion, to reduce any potential bias caused by fragmentation and/or sample distribution.…”

“…All pots were maintained in a growth chamber under controlled conditions, at a photosynthetic photon flux density (PPFD) of 350 μmol photons m –2 s –1 with a photoperiod of 20/4 h light/dark, 75% relative humidity, and at 4°C. All pots were watered with 20 ml of water once per week, mimicking current water availability in Maritime Antarctica during a typical growing season ( Barrera et al, 2020 ; Hereme et al, 2020 ).…”

Fungal Symbionts Enhance N-Uptake for Antarctic Plants Even in Non-N Limited Soils

“…in previous experiments made by our research group (Ramos et al, 2018;Barrera et al, 2020;Hereme et al, 2020). After 4 weeks, endophyte infection was assessed by counting aniline blue-stained fungal hyphaes in root cross-sections in 10% of the produced plants as the percentage of infested root length (Bacon and White, 2000).…”