Conjugated polyamines are involved in conformation stability of plasma membrane from maturing maize grain embryos under drought stress

Abstract

Polyamines are closely associated with drought stress in plants. However, the function which polyamines play in the maturing maize grain under drought is not still clear. Especially, whether the conjugated polyamines are involved in H + -ATPase activity and conformation of plasma membrane remains to be answered. Therefore, in the study, the contents of conjugated polyamines, H + -ATPase activity and conformation of plasma membrane were detected with maturing grain embryos of two maize ( Zea mays L.) cultivars, which were different in drought stress-tolerance. Under drought stress, the cell plasmolysis of the drought-sensitive Xundan No. 22 cv. was more marked than that of the drought-tolerant Yedan No. 13 cv., while the increases in the contents of conjugated non-covalently spermidine and spermine, conjugated covalently putrescine and spermidine in plasma membrane from Yedan 13 were more obvious than those in Xundan 22. The results suggested that these conjugated polyamines might be involved in stability of plasma membrane. Furthermore, H + -ATPase activity in plasma membrane from Yedan 13 increased more significantly than that in Xundan 22, indicating that these conjugated polyamines were closely correlated with the activity of H + -ATPase. To justify further the inferences, the additional experiments with exogenous spermidine, spermine and polyamine biosynthesis inhibitors were carried out in the study. The results showed that the application of exogenous spermidine or spermine increased the levels of conjugated polyamines in plasma membrane, coupled with alleviating cell plasmolysis and increasing H + -ATPase activity. The application of inhibitors decreased the levels of conjugated polyamines, coupled with aggravating cell plasmolysis and decreasing H + -ATPase activity. From these results together, it could be concluded that non-covalently conjugated spermidine and spermine, conjugated covalently putrescine and spermidine in plasma membrane functioned in increasing H + -ATPase activity, mitigating cell plasmolysis and maintaining the plasma membrane conformation of the maturing maize grain embryos under drought stress. • Drought stress increased the levels of conjugated PAs in plasma membrane. • Conjugated PAs in plasma membrane mitigated cell plasmolysis induced by drought. • Conjugated PAs enhanced the H + -ATPase activity in plasma membrane under drought. • Conjugated PAs in plasma membrane were closely associated with drought tolerance.