The Panax ginseng PgTIP1 gene confers enhanced salt and drought tolerance to transgenic soybean plants by maintaining homeostasis of water, salt ions and ROS

The Panax ginseng PgTIP1 gene has been demonstrated to have high water channel activity by its heterologous expression in Xenopus laevis oocytes and in yeast, and it also plays significant roles in enhancing the salt/drought tolerance of PgTIP1-transgenic Arabidopsis plants and salt adaptation of PgTIP1-transformed Glycine max. In this work, PgTIP1 gene was transformed into the hybrid soybean strain 4076 (F5), which was selected for salt tolerance generation by generation from the cross assembly of G. max N23674 cultivar × G. soja BB52 accession. The PgTIP1-transgenic soybean plants mediated by the pollen tube pathway, represented by lines L19 and L29, were simultaneously analyzed at physiological and molecular levels for enhanced salt and drought tolerance. The results showed that the salt-stressed PgTIP1-transgenic lines L19 and L29 acquired better leaf stomatal movement and water-gas exchange capacity; less absorption, transport and accumulation of Na+, Cl−; a lower Na+/K+ ratio; and enhanced antioxidase activities of SOD, POD, CAT, and APX than WT in the roots and leaves. Under PEG-induced drought stress, the PgTIP1-transgenic plants showed greater leaf water-retention capacity and reduced cell membrane damage in roots and leaves. Therefore, the PgTIP1-transgenic soybean lines showed both salt and drought tolerance, which are related not only to the primary functions of the PgTIP1 gene in terms of water status regulation but also to its secondary roles in up-regulating the expression of stress-related genes (GmNHX1, GmSOS1, GmCLC1, GmCAT1, GmAPX1, GmNCED1 and GmP5CS1), which are involved in homeostasis of Na+, K+, and Cl−; ROS scavenging; and synthesis of ABA, proline, etc.