Abstract
Dehydrin is a type of late embryogenesis abundant (LEA) protein. The dehydrin genes, HbDHN1 and HbDHN2, in Hevea brasiliensis were previously found to be induced at the wounding site of epicormic shoots, with local tissue dehydration identified as the key signal for laticifer differentiation. However, the exact role of the HbDHNs remains unknown. In this study, HbDHN1 and HbDHN2 expression was examined under multiple abiotic stresses; namely, cold, salt, drought, wounding, abscisic acid (ABA), ethylene (ET), and jasmonic acid (JA) treatment. Although, both HbDHNs were defined as SK2-type dehydrin, they showed different cellular localizations. Overexpression of the HbDHNs in Arabidopsis thaliana further revealed a significant increase in tolerance to salt, drought and osmotic stresses. Increased accumulation of proline and a reduction in electrolyte leakage were also observed under salt and drought stress, and a higher water content was indicated under osmotic stress. The transgenic plants also showed higher activity levels of ascorbate peroxidase (APX), superoxide dismutase (SOD) and catalase, and accumulated less hydrogen peroxide (H2O2) and superoxide (). Given that reactive oxygen species (ROS) are thought to be a key signal for laticifer differentiation, these findings suggest that HbDHNs act as ROS scavengers, directly or indirectly affecting laticifer differentiation. Both HbDHNs therefore influence physiological processes, improving plant tolerance to multiple abiotic stresses.
Highlights
Plants are subjected to various abiotic stresses from low temperature and drought to salinity
Several stress response-related cis-acting elements, including ABRE, DRE, TGACG palindrome, and LTR motifs, were revealed in both the HbDHN1 and HbDHN2 promoters (Table S2). These elements are involved in abscisic acid (ABA), drought, low-temperature, and jasmonic acid (JA) signaling pathways, suggesting that expression of HbDHN1 and HbDHN2 is regulated by multiple abiotic stresses
The HbDHN2-GFP fusion protein remained at the edge of the cell and seemed to localize in the plasma membrane (Figure 1B). These findings suggest that the protoplast is more advantageous than the epidermis for GFP fusion protein localization and confirm that HbDHN1 and HbDHN2 are both SK2-type dehydrins; differentiated cellular localization suggests that they play different roles in cell physiological processes
Summary
Plants are subjected to various abiotic stresses from low temperature and drought to salinity. To survive, they have evolved several different mechanisms to enhance their overall tolerance, including stress signal perception and transduction, and associated molecular regulatory networks. The first group contains proteins involved in the regulation of signal transduction and stress-inducible gene expression, and includes transcription factors and protein kinases (e.g., MAP kinases, phosphatases, and phospholipid metabolic enzymes). Dehydrins (DHNs) belong to the group 2 LEA protein family. They were redefined based on the existence of at least one copy of a highly conserved 15-amino acid lysine-rich K-segment
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