PEG胁迫对偏关苜蓿脯氨酸代谢途径关键酶的影响

以山西地方品种偏关苜蓿(Medicago sativa cv.Pianguan)为试验材料,采用20%聚乙二醇(PEG-6000)分别处理不同时间(0,8,16,24,32,48和72h),研究偏关苜蓿地上部及地下部的脯氨酸(proline,Pro)含量、鸟氨酸δ-氨基转移酶(ornithine-oxo-acidtransaminase,δ-OAT)、吡咯啉-5-羧酸合成酶(pyrroline-5-carboxylate synthetase,P5CS)、脯氨酸脱氢酶(proline dehydragenase,ProDH)活性的动态变化。结果表明:PEG胁迫下,地上部Pro含量显著高于地下部,PEG处理40h时,地上部Pro含量最高(3230.4μg·g^-1 FW)。地上部和地下部P5CS活性呈"升-降-升-降"的变化趋势。δ-OAT活性则在胁迫8h时升高,之后下降。ProDH活性受PEG胁迫显著降低,呈时间依赖性。PEG胁迫前期,偏关苜蓿的Pro积累以鸟氨酸-脯氨酸途径为主,随胁迫时间的延长,逐渐转为以谷氨酸-脯氨酸途径为主。

Effect of PEG Stress on Key Enzymes Involved in Proline Metabolism of Medicago sativa cv.Pianguan

Medicago sativa cv.Pianguan is an important local variety in Pianguan of Shanxi province.This study focuses on the dynamic changes og proline(Pro) content and the activities of pyrroline-5-carboxylate synthetase(P5CS),ornithine-oxo-acid transaminase(δ-OAT) and proline dehydragenase(ProDH) in both aboveground and underground parts of Medicago sativa cv.Pianguan under PEG-6000 stress for 0,8,16,24,32,48 and 72 h,respectively.The proline content of aboveground parts was the highest(3230.4 μg·g-1 FW) when stressed for 40 h,which is significantly greater than that of underground parts.P5CS activity showed a tendency of rising-declining-rising-declining,while the δ-OAT activity was rising initially when stressed for 8 h,then declining.ProDH activity significantly declined for both aboveground and underground parts with increasing PEG-6000 stress time.In the earlier stage of PEG stress,the ornithine-proline pathway is the main style for Medicago sativa cv.Pianguan responding to PEG stress,but the glutamate-proline pathway would gradually take over the predominant role with the time extending of PEG stress.