外源钙对低温胁迫下西藏野生垂穗披碱草生理及相关基因表达的影响

为探究Ca²⁺调控西藏野生垂穗披碱草（Elymus nutans）适应低温的生理和分子响应机制，本研究采用叶面喷施外源CaCl₂的方法，研究其对当雄野生垂穗披碱草表型，生物量，电解质渗透率、活性氧、丙二醛、渗透调节物质含量以及抗氧化酶活性的影响。结果表明，喷施15 mM CaCl₂有效地缓解低温对垂穗披碱草幼苗的生长抑制；CaCl₂处理显著提高低温胁迫下垂穗披碱草地上/地下生物量，降低丙二醛和活性氧的积累，提高可溶性糖和游离脯氨酸的含量及过氧化物酶、过氧化氢酶、超氧化物歧化酶、抗坏血酸过氧化氢酶等抗氧化酶活性。RT-qPCR结果表明，外源CaCl₂能上调EnAPX，EnCAT2，EnGPX，EnGST4，EnMDAR，EnPER1，EnCu/ZnSOD，EnFeSOD，EnMnSOD抗氧化酶基因的表达水平，同时上调胁迫相关基因EnCOR410，EnCS120，EnDHN5和EnMYB4的表达。综上，低温胁迫下适宜浓度的Ca²⁺能够激活抗氧化酶活性，及时清除过量积累的活性氧，缓解低温对西藏野生垂穗披碱草细胞膜系统造成的氧化伤害，提高细胞渗透调节能力，并且能够诱导胁迫相关基因的表达，从而提高垂穗披碱草的抗寒性。

Effects of Exogenous Calcium on Physiology and Related Gene Expression of Elymus nutans under Cold Stress

In the present study,we used Damxung wild Elymus nutans as the material to investigate the physiological and molecular mechanism of exogenous CaCl₂ mediating cold tolerance. The effects of CaCl₂ on above and below-ground biomass,electrolyte permeability,reactive oxygen species,malondialdehyde,osmotic adjustment substances,and antioxidant protective enzyme activities in the leaves of the E. nutans plants were measured. The results showed that exogenous 15 mM CaCl₂ application increased the above and below-ground biomass,the content of soluble sugars and free proline,improved POD,CAT,SOD,APX activities,and decreased the accumulation of malondialdehyde content under cold stress. An RT-qPCR data displayed that exogenous CaCl₂ significantly induced the expression levels of nine antioxidant enzyme genes,including EnAPX,EnCAT2,EnGPX,EnGST4,EnMDAR,EnPER1,EnCu/ZnSOD,and EnFeSOD,EnMnSOD, and up-regulated the expression level of stress-related genes such as EnCOR410,EnCS120, EnDHN5,and EnMYB4. These results indicated that appropriate concentration of Ca²⁺ could alleviate the damage induced by cold stress in the leaves of E. nutans via improving the activities of antioxidant enzyme and the contents of osmoregulation substances,scavenging the excessive accumulation of reactive oxygen species,and up-regulating the expression of the genes involved in some antioxidant enzymes and cold stress-related response.