Cerebroside C Increases Tolerance to Chilling Injury and Alters Lipid Composition in Wheat Roots

Chilling tolerance was increased in seed germination and root growth of wheat seedlings grown in media containing 20 µg/mL cerebroside C (CC), isolated from the endophytic Phyllosticta sp. TG78. Seeds treated with 20 µg/mL CC at 4°C expressed the higher germination rate (77.78%), potential (23.46%), index (3.44) and the shorter germination time (6.19 d); root growth was also significantly improved by 13.76% in length, 13.44% in fresh weight and 6.88% in dry mass compared to controls. During the cultivation process at 4°C for three days and the followed 24 h at 25°C, lipid peroxidation, expressed by malondialdehyde (MDA) content and relative membrane permeability (RMP) was significantly reduced in CC-treated roots; activities of lipoxygenase (LOX), phospholipid C (PLC) and phospholipid D (PLD) were inhibited by 13.62–62.26%, 13.54–63.93% and 13.90–61.17%, respectively; unsaturation degree of fatty acids was enhanced through detecting the contents of CC-induced linoleic acid, linolenic acid, palmitic acid and stearic acid using GC-MS; capacities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were individually increased by 7.69–46.06%, 3.37–37.96%, and −7.00–178.07%. These results suggest that increased chilling tolerance may be due, in part, to the reduction of lipid peroxidation and alternation of lipid composition of roots in the presence of CC.

从内生叶点霉属（Phyllosticta）菌株TG78中分离得到的脑苷脂C（cerebroside C, CC），可提升生长于含20 µg/mL该物质培养基中小麦种子萌发与幼苗根系生长阶段的耐寒性。在4℃条件下经20 µg/mL CC处理的小麦种子，其萌发率（77.78%）、萌发势（23.46%）与萌发指数（3.44）均显著更高，且萌发时长更短（6.19 d）；与对照组相比，处理组根系长度增加13.76%、鲜重增加13.44%、干重增加6.88%，根系生长得到显著改善。在4℃培养3天、随后于25℃培养24小时的过程中，经CC处理的小麦根系中，以丙二醛（malondialdehyde, MDA）含量与相对膜渗透性（relative membrane permeability, RMP）为表征指标的脂质过氧化水平显著降低；脂氧合酶（lipoxygenase, LOX）、磷脂酶C（phospholipid C, PLC）与磷脂酶D（phospholipid D, PLD）的活性分别被抑制13.62%~62.26%、13.54%~63.93%与13.90%~61.17%；通过气相色谱-质谱联用（GC-MS）检测CC诱导下的亚油酸、亚麻酸、棕榈酸与硬脂酸含量，发现根系脂肪酸的不饱和度得以提升；超氧化物歧化酶（superoxide dismutase, SOD）、过氧化氢酶（catalase, CAT）与谷胱甘肽过氧化物酶（glutathione peroxidase, GSH-Px）的活性分别提升7.69%~46.06%、3.37%~37.96%与−7.00%~178.07%。上述结果表明，CC存在下小麦耐寒性的提升，可能部分归因于根系脂质过氧化水平的降低与脂质组成的改变。