Enhanced Tolerance to Chilling Stress in Tomato by Overexpression of a Mitogen-Activated Protein Kinase, SlMPK7
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Low temperature is one of the most common environmental stresses affecting plant growth and agricultural production. The mitogen-activated protein kinase (MAPK) cascade plays a pivotal role in diverse signaling pathways related to plant development and stress responses. In this study, a novel MAPK gene, SlMPK7, in tomato (Solanum lycopersicum) belonging to group B MAPK was isolated and functionally characterized. QRT-PCR analysis revealed that transcription of the MAPK SlMPK7 in tomato leaves was triggered by abiotic stresses and exogenous signaling molecules. Moreover, hydrogen peroxide (H2O2) and Ca2+ mediated 4 °C-induced upregulated expression of SlMPK7 at the messenger RNA (mRNA) level. SlMPK7 was predominantly localized in the nucleus. Transgenic tomato overexpressing SlMPK7 accumulated less reactive oxygen species (ROS), more superoxide dismutase, peroxidase, catalase activities, more proline and soluble sugar contents, and more stress-responsive gene expression, leading to enhanced chilling stress tolerance compared with the wild-type plants. Collectively, these data demonstrate that SlMPK7 acts as a positive regulator in the response to chilling stress by regulating ROS homeostasis through activation of cellular antioxidant systems and modulating the transcription of stress-associated genes.
KeywordsTomato MAPK SlMPK7 Chilling stress Reactive oxygen species Transgenic tomato
We thank the editors and reviewers for their critical reading and constructive suggestions. This work was funded by Shanghai Academy of Agricultural Sciences Fund for Young Scholars (Nong Ke Qing Nian Ke Ji NO.2012-06), Special Fund for Agro-scientific Research in the Public Interest (NO.201403032), and Young Talents Plan in Shanghai Agricultural System (Hu Nong Qing Zi NO.2015-1-19).
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