Tibbett M, Sanders F E, Cairney J W G
School of Biology, University of Leeds, UK.
Mycorrhiza. 2002 Oct;12(5):249-55. doi: 10.1007/s00572-002-0183-8. Epub 2002 Jul 4.
Ectomycorrhizal fungi have been shown to survive sub-zero temperatures in axenic culture and in the field. However, the physiological basis for resistance to freezing is poorly understood. In order to survive freezing, mycelia must synthesise compounds that protect the cells from frost damage, and certain fungal-specific soluble carbohydrates have been implicated in this role. Tissue concentrations of arabitol, mannitol and trehalose were measured in axenic cultures of eight Hebeloma strains of arctic and temperate origin grown at 22, 12, 6 and 2 degrees C. In a separate experiment, mycelia were frozen to -5 degrees C after pre-conditioning at either 2 degrees C or 22 degrees C. For some, especially temperate strains, there was a clear increase in specific soluble carbohydrates at lower growth temperatures. Trehalose and mannitol were present in all strains and the highest concentrations (close to 2.5% and 0.5% dry wt.) were recorded only after a cold period. Arabitol was found in four strains only when grown at low temperature. Cold pre-conditioning enhanced recovery of mycelia following freezing. In four out of eight strains, this was paralleled by increases in mannitol and trehalose concentration at low temperature that presumably contribute towards cryoprotection. The results are discussed in an ecological context with regard to mycelial overwintering in soil.
外生菌根真菌已被证明能在无菌培养和野外环境中耐受零下温度。然而，人们对其抗冻的生理基础了解甚少。为了在冷冻条件下存活，菌丝体必须合成能保护细胞免受冻害的化合物，某些真菌特有的可溶性碳水化合物被认为起到了这一作用。在22℃、12℃、6℃和2℃下培养的8种来自北极和温带的Hebeloma菌株的无菌培养物中，测定了阿拉伯糖醇、甘露醇和海藻糖的组织浓度。在另一个实验中，菌丝体在2℃或22℃预处理后被冷冻至-5℃。对于一些菌株，尤其是温带菌株，在较低生长温度下，特定的可溶性碳水化合物明显增加。所有菌株中都存在海藻糖和甘露醇，只有在经历一段低温期后才记录到最高浓度（接近干重的2.5%和0.5%）。只有在低温下生长时，才在4种菌株中发现了阿拉伯糖醇。低温预处理提高了冷冻后菌丝体的恢复能力。在8种菌株中的4种中，这与低温下甘露醇和海藻糖浓度的增加同时出现，这可能有助于抗冻保护。本文从生态学角度讨论了菌丝体在土壤中越冬的相关结果。
