γ-氨基丁酸对低氧胁迫下甜瓜幼苗多胺代谢的影响

Effects of exogenous γ-aminobutyric acid on polyamine metabolism of melon seedlings under hypoxia stress

以‘西域一号’甜瓜为试验材料,采用营养液水培法,研究了低氧胁迫下外源添加γ-氨基丁酸(GABA)对甜瓜幼苗多胺代谢的影响.结果表明:与通气对照相比,低氧胁迫处理的甜瓜幼苗谷氨酸脱羧酶(GAD)活性和GABA含量显著提高,同时多胺合成酶活性提高诱导多胺含量显著增加,但二胺氧化酶(DAO)和多胺氧化酶(PAO)活性也显著提高;根系精氨酸脱羧酶(ADC)活性提高幅度较大,导致根系游离态腐胺含量较高,而叶片鸟氨酸脱羧酶(ODC)和S-腺苷甲硫氨酸脱羧酶(SAMDC)活性提高幅度较大,导致叶片游离态亚精胺(Spd)含量较高;根系游离态DAO和PAO活性显著低于叶片,其细胞壁结合态PAO活性显著高于叶片.与低氧胁迫处理相比,低氧胁迫下外源添加GABA处理的甜瓜幼苗叶片和根系中GABA和谷氨酸含量均显著提高,而GAD活性显著降低;精氨酸、鸟氨酸、甲硫氨酸含量的提高促使多胺合成酶活性显著提高,从而诱导多胺含量显著增加,DAO和PAO活性显著降低.

Taking melon cultivar ＇Xiyu No. 1＇ as test material, a hydroponic experiment was dueted to investigate the effects of exogenous ,y-aminobutyric acid （GABA） on the seedlings amine metabolism under hypoxia stress. Compared with the control in normoxic treatment, the conpoly- seedlings under hypoxia stress had significantly higher glutamic acid decarboxylase （GAD） activity and GABA content, and their polyamine synthesis enzymes activities all enhanced significantly, which led to a marked increase of polyamines contents. Meanwhile, the seedlings leafand root diamine oxidase （DAO） and polyamine oxidase （PAO） activities also had a significant increase. The increment of root arginine decarboxylase （ADC） activity was higher, which induced a higher content of free putrescine （Put） in roots, while the increment of leaf ornithine decarboxylase （ODC） and S-adenosylmethionine decarboxylase （SAMDC） activities were higher, inducing a higher content of free spermidine （Spd） in leaves. The PBs-extractable DAO and PAO activies in roots were significantly lower than those in leaves, but the cell wall-bound PAO activity was in adverse. Under hypoxia stress, the addition of exogenous GABA increased the leaf- and root GABA and glutamic acid contents and decreased the GAD activity significantly. The increase of arginine, ornithine, and methionine contents promoted the activities of polyamines synthesis enzymes, which led to the significant increase of polyamines contents and the significant decrease of DAO and PAO activities.