Biochemical and ecophysiological responses to manganese stress by ectomycorrhizal fungus Pisolithus tinctorius and in association with Eucalyptus grandis

Abstract

At relatively low concentrations, the element manganese (Mn) is essential for plant metabolism, especially for photosynthesis and as an enzyme antioxidant cofactor. However, industrial and agricultural activities have greatly increased Mn concentrations, and thereby contamination, in soils. We tested whether and how growth of Pisolithus tinctorius is influenced by Mn and glucose and compare the activities of oxidative stress enzymes as biochemical markers of Mn stress. We also compared nutrient accumulation, ecophysiology, and biochemical responses in Eucalyptus grandis which had been colonized by the ectomycorrhizal Pisolithus tinctorius with those which had not, when both were exposed to increasing Mn concentrations. In vitro experiments comprised six concentrations of Mn in three concentrations of glucose. In vivo experiments used plants colonized by Pisolithus tinctorius, or not colonized, grown with three concentrations of Mn (0, 200, and 1000 μM). We found that fungal growth and glucose concentration were correlated, but these were not influenced by Mn levels in the medium. The anti-oxidative enzymes catalase and glutathione S-transferase were both activated when the fungus was exposed to Mn. Also, mycorrhizal plants grew more and faster than non-mycorrhizal plants, whatever Mn exposure. Photosynthesis rate, intrinsic water use efficiency, and carboxylation efficiency were all inversely correlated with Mn concentration. Thus, we originally show that the ectomycorrhizal fungus provides protection for its host plants against varying and potentially toxic concentrations of Mn.

Effects of manganese and zinc on the growth process of Phytophthora nicotianae and the possible inhibitory mechanisms

“…High concentrations of Mn are toxic to P. nicotianae due to membrane lipid peroxidation from the imbalance in the antioxidant system. These results were consistent with the findings of Li et al (2012), Canton et al (2016 and Li et al (2012). With increasing Zn concentration, CAT activity and SOD activity decreased slightly, then reached their maximum values and finally decreased.…”

“…These results illustrated that Mn and Zn affected the balance of the antioxidant system in P. nicotianae. Similar findings have been reported in recent studies (Li et al, 2012;Canton et al, 2016).…”

“…Phytophthora nicotianae is an important pathogenic microorganism with a wide range of hosts; the fungus causes root and stem diseases of various crops (Bittner & Mila, 2016). Previous research (Baider & Cohen, 2003;Helfenstein et al, 2015;Shi et al, 2006) reported positive effects of manganese-containing fungicides and zinc-containing agents on fungal diseases.…”

Physiological and molecular mechanisms of heavy metal accumulation in nonmycorrhizal versus mycorrhizal plants

“…The antioxidative system includes enzymatic and nonenzymatic antioxidants. Higher antioxidative enzyme activities have been frequently reported in mycorrhizal plants and may contribute to the scavenging of HM‐induced ROS (Canton et al, ; Rozpądek et al, ). Recently, it was showed that the activities of superoxide dismutase, ascorbate peroxidases, and glutathione peroxidase are elevated in arbuscular‐mycorrhizal Robinia pseudoacacia L., which probably contributes to the alleviation of Pb‐induced toxicity (Yang et al, ).…”

Soil propagule bank of ectomycorrhizal fungi associated with Masson pine (Pinus massoniana) grown in a manganese mine wasteland

“…and disturb their absorption, translocation [ 17 ], excess Mn causes chlorosis and necrosis, the appearance of brown, necrotic spots or small reddish purple spots and sometimes, dark root tips [ 18 ]. ECM symbiosis could protect its host plants against the toxic effect of Manganese (Mn) [ 19 ]. Mn pollution could also affect fungal populations by reducing the abundance of some groups of ECM fungi [ 14 , 16 ].…”