Abstract
Mitogen-activated protein kinase (MAPK) cascades play pivotal roles in mediating biotic and abiotic stress responses. Cotton (Gossypium hirsutum) is the most important textile crop in the world, and often encounters abiotic stress during its growth seasons. In this study, a gene encoding a mitogen-activated protein kinase (MAPK) was isolated from cotton, and designated as GhMPK17. The open reading frame (ORF) of GhMPK17 gene is 1494 bp in length and encodes a protein with 497 amino acids. Quantitative RT-PCR analysis indicated that GhMPK17 expression was up-regulated in cotton under NaCl, mannitol and ABA treatments. The transgenic Arabidopsis plants expressing GhMPK17 gene showed higher seed germination, root elongation and cotyledon greening/expansion rates than those of the wild type on MS medium containing NaCl, mannitol and exogenous ABA, suggesting that overexpression of GhMPK17 in Arabidopsis increased plant ABA-insensitivity, and enhanced plant tolerance to salt and osmotic stresses. Furthermore, overexpression of GhMPK17 in Arabidopsis reduced H2O2 level and altered expression of ABA- and abiotic stress-related genes in the transgenic plants. Collectively, these data suggested that GhMPK17 gene may be involved in plant response to high salinity and osmotic stresses and ABA signaling.
Highlights
Plant growth is significantly affected by a range of environmental stresses, such as drought, high salinity, pathogen infection, cold and freezing
A highly conserved mitogen-activated protein kinase (MAPK) cascade consists of three steps: MAPKs are activated through phosphorylation on two threonine and tyrosine residues by upstream MAPK kinase (MAPKK), which are in turn phosphorylated on two serine/threonine residues by MAPKK kinase (MAPKKK) [3,4]
Several signals are triggered by high salinity and hyperosmotic stresses including reactive oxygen species (ROS) formation, PLD-mediated phosphatidic acid production, increment of cytosolic Ca2+ concentrations and accumulation of nitric oxide [31,32,33,34]
Summary
Plant growth is significantly affected by a range of environmental stresses, such as drought, high salinity, pathogen infection, cold and freezing. Plants have developed a great ability to adapt the changes in the environment. They are equipped with sophisticated mechanisms, such as the perception and transduction of stress stimuli. The mitogen-activated protein kinase (MAPK) signaling pathway is an elaborate and intricate complex that are highly conserved in eukaryotes and play important roles in response to various biotic and abiotic stresses [1,2]. Each mitogen-activated protein kinase (MAPK) cascade is known to be one of the major phosphorylation pathways which are composed of three kinases, MAPK, MAPK kinase (MAPKK), MAPKK kinase (MAPKKK) and function downstream of sensors/receptors to regulate cellular responses. Activated MAPKs regulate the activities of diverse targets including transcription factors [5], cytoskeletal proteins [6], and other protein kinases [7]
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