γ-氨基丁酸对低氧胁迫下甜瓜幼苗抗氧化酶活性及表达的影响

Effect of γ-aminobutyric acid on activities and expression of antioxdative enzyme in melon seedlings under hypoxia stress

采用营养液水培方法，研究低氧胁迫下外源GABA对甜瓜幼苗抗氧化酶（SOD、POD、CAT和APX）活性和同工酶表达的影响，采用实时荧光定量PCR方法检测幼苗根系抗氧化酶的基因表达特性。结果表明，低氧胁迫处理下，幼苗根系和叶片抗氧化酶活性和同工酶表达均高于对照，且根系CmSOD、CmPOD1、CmPOD2、CmCAT、CmAPX基因均上调表达；低氧胁迫下外源GABA处理显著提高幼苗根系和叶片SOD、CAT和APX活性以及同工酶表达，且根系CmSOD、CmCAT、CmAPX基因相对表达量在0.5~1 d迅速提高并达到最大值，且增加幅度高于低氧胁迫处理。由此可知，GABA通过促进根系抗氧化酶基因快速大量表达，提高抗氧化酶活性和同工酶的表达量，从而缓解低氧胁迫对甜瓜幼苗的伤害。

This paper investigated the effects of exogenous γ-aminobutyric acid on antioxdative enzyme （SOD, POD, CAT and APX） activities and isozyme expression of melon seedlings under hypoxia stress with hydroponics culture. Meanwhile the characteristics of antioxdative enzyme gene expression of melon seedlings roots were detected by the real-time fluorescent quantitative （RT-PCR）. The results showed that the antioxdative enzyme activities and isozyme expression in melon seedlings roots and leaves were higher under hypoxia stress than those under normoxic treatment （control） as wel as the gene expression of CmSOD, CmPOD1, CmPOD2, CmCAT, CmAPX in melon roots were up-regulated. Exogenous GABA application under hypoxia stress could significantly increased the activities and isozyme expression of SOD,CAT and APX in seedlings roots and leaves. Futhermore, the gene expression levels of CmSOD, CmCAT, CmAPX in roots rapid increased and reached the maximum value after 0.5-1 d with GABA application under hypoxia stress, that increasing extent higher than hypoxia stress treatment. The results suggested that exogenous GABA al eviated the harm of hypoxia tolerance in melon seedlings by promoting rapidly and largely antioxdative enzyme gene expression as wel as increasing antioxdative enzyme activities and isozyme expression in melon seedlings.