Effect Of Antioxidant Enzyme System Of Acacia Auriculiformis Response To Acid Stress

Hydroculture experiments were carried out to investigate the physiological response especially the antioxidant enzymes of Acacia auriculiformis seedlings to acid stress.Seedlings were treated at two p H levels regulated by H2SO4: p H 2.0 and 3.0,as well as the contrast to the control(CK)of p H 5.8,at two time scale(3 and 9 days respectively).Effects of the acid stress on metabolic products were assessed by measuring the contents of malondialdehyde(MDA)and proline(Pro)and the activities of different antioxidant enzymes in seedling leaves,including the peroxidase(POD),glutathione S-transferases(GST),glutathione peroxidase(GPX)and glutathione reductase(GR).The results showed that the proline content exhibited an insignificant difference at p H 3.0,but a significant increase at p H 2.0 compared to CK,indicated that the seedling encountered severe stress at p H 2.0.MDA content at both p H 3.0 or p H 2.0 didn’t show any significant differences from CK,suggested that membrane lipid might not severely peroxidated under a strong acid stress.Compared to CK,the activities of enzymes such as GST and GPX significantly increased at p H 3.0,but did not significantly change at p H 2.0.On the contrary,the activities of GR and POD showed no significant differences at p H 3.0,but significantly decreased at p H 2.0,which suggested the response patterns of these enzymes were different to strong acid,while GST was most sensitive to strong acid s tress.Besides,high-throughput RNAsequencingtechniqueswas used to reveal the transcriptomic response of A.auriculiformis to acid stress,from which11 differentially expressed unigenes wereobtained,which were predicted to code for GPX,GR and P5 CR.The expression level of unigenepredicted to code for GPX,GR and P5 CR were induced by 3-day acid stress,which was consistent with the result of transcriptional sequencing results,but showed different responses amongunigenes.The relative expression of unigene predicted to code for GPX and P5 CR increased with the increasing of acis stress intensity,but the expression of unigene encoding GR showed the opposite trend.In general,we think p H 3.0 could be a threshold below which the seedlings of A.auriculiformis were difficult to adapt in physiological metabolism.