Abstract
Abiotic stresses have negative effects on plants growth and development. Plants, being sessile, have developed specific adaptive strategies that allow them to rapidly detect and respond to abiotic stress factors. The detoxification efflux carriers (DTX)/multidrug and toxic compound extrusion (MATE) transporters are of significance in the translocation of abscisic acid (ABA), a phytohormone with profound role in plants under various abiotic stress conditions. The ABA signaling cascades are the core regulators of abiotic stress responses in plants, triggering major changes in gene expression and adaptive physiological responses. We therefore carried out genome-wide analysis of the DTX/MATE gene family, transformed a DTX/MATE gene in Arabidopsis and carried out functional analysis under drought, salt, and cold stress conditions. We identified 128, 70, and 72 DTX/MATE genes in Gossypium hirsutum, Gossypium arboreum, and Gossypium raimondii, respectively. The proteins encoded by the DTX/MATE genes showed varied physiochemical properties but they all were hydrophobic. The Gh_D06G0281 (DTX/MATE) over-expressing Arabidopsis lines were highly tolerant under drought, salt, and cold stress with high production of antioxidant enzymes and significantly reduced levels of oxidants. Lipid peroxidation, as measured by the level of malondialdehyde concentrations was relatively low in transgenic lines compared to wild types, an indication of reduced oxidative stress levels in the transgenic plants. Based on physiological measurements, the transgenic plants exhibited significantly higher relative leaf water content, reduced excised leaf water loss and a significant reduction in ion leakage as a measure of the cell membrane stability compared to the wild types. Abiotic stress responsive genes, ABF4, CBL1, SOS1, and RD29B were highly expressed in the transgenic lines compared to the non-transformed wild type plants. The protein encoded by the Gh_D06G0281 (DTX/MATE) gene was predicted to be located within the plasma membrane. Since signals from extracellular stimuli are transmitted through the plasma membrane most of which are conducted by plasma membrane proteins it is possible the Gh_D06G0281 (DTX/MATE) gene product could be important for this process.
Highlights
Abiotic stresses such as drought, salinity, heat, cold among others continue to compromise plant growth and crop yield among the agricultural crops (Change and Production, 2010)
We identified 128, 72 and 70 genes that encode the detoxification efflux carriers (DTX)/multidrug and toxic compound extrusion (MATE) proteins in G. hirsutum, G. raimondii, and G. arboreum, respectively (Table 2)
The widest range in protein length was observed in G. hirsutum, while in G arboreum, the lengths of the putative DTX/MATE proteins ranged from 84 to 722 aa, while in the lengths of putative DTX/MATE proteins G. raimondii ranged from 133 aa to 601 aa
Summary
Abiotic stresses such as drought, salinity, heat, cold among others continue to compromise plant growth and crop yield among the agricultural crops (Change and Production, 2010). Plants have evolved complex survival strategies to enhance their tolerance levels to both abiotic and biotic stress factors (Nakashima and YamaguchiShinozaki, 2006). Expression levels of certain genes has been shown to increase in response to various stress factors such as salinity, cold, drought and oxidative stress (Fang et al, 2015). The molecular mechanisms involved in drought, salt, and cold stress acclimation have been extensively investigated, and several molecules have been identified that are important for enhancing tolerance to these abiotic stresses (Huang et al, 2012). Salinity-inducible genes are believed to either function as protectants or by promoting the synthesis of the osmoprotectants, detoxification enzymes, ion channels, and transporters (Rabbani, 2003)
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