EXPRESSION PATTERN OF ALNHA1 IN Aeluropus littoralis UNDER HEAVY METALS STRESS

Na+/H+ antiporter proteins are up- or down- regulated under various abiotic stresses. An experiment was carried out in a completely randomized design with three replications to analyze the expression profile of AlNHA1, a gene encoding a plasma membrane Na+/H+ antiporter, in Aeluropus littoralis using semi-quantitative PCR and real-time PCR. In general, the expression level of AlNHA1 was increased with increasing external heavy metals supply levels and its expression was positively associated with heavy metals content of leaves. The results also showed that the AlNHA1 expression level was not exactly the same for all heavy metals and at different time points after treatment with each metal. In Ag-treated plants, AlNHA1 mRNA level was elevated just after 6 h and after that it decreased to control level, while, in other treatments, the mRNA levels were more than control. Root length and weight were mostly affected in both levels of heavy metals but shoot length was not affected. The weight of roots decreased under heavy metals treatments, except lead, and the length of root decreased under all treatments. Obtained results revealed that this species absorbs and accumulates Ag more than other heavy metals and probably has higher tolerance to Ag than other metals. The results also revealed a favorable correlation between quantitative and semi-quantitative PCR analysis. It may be concluded that AlNHA1 may serve to exclude the heavy metal ions from the plant cells and plays a critical role in the response of this species to heavy metals stresses.