Abstract
BackgroundHigh temperature is a major environmental stress that limits plant growth and agriculture productivity. Mitogen-activated protein kinases (MAPKs) are highly conserved serine and threonine protein kinases that participate in response to diverse environmental stresses in plants. A total of 16 putative SlMAPK genes are identified in tomato, and SlMAPK3 is one of the most extensively studied SlMAPKs. However, the role of SlMAPK3 in response to heat stress is not clearly understood in tomato plants. In this study, we performed functional analysis of SlMAPK3 for its possible role in response to heat stress.ResultsqRT-PCR analyses revealed that SlMAPK3 relative expression was depressed by heat stress. Here, wild-type (WT) tomato plants and CRISPR/Cas9-mediated slmapk3 mutant lines (L8 and L13) were used to investigate the function of SlMAPK3 in response to heat stress. Compared with WT plants, slmapk3 mutants exhibited less severe wilting and less membrane damage, showed lower reactive oxygen species (ROS) contents, and presented higher both activities and transcript levels of antioxidant enzymes, as well as elevated expressions of genes encoding heat stress transcription factors (HSFs) and heat shock proteins (HSPs).ConclusionsCRISPR/Cas9-mediated slmapk3 mutants exhibited more tolerance to heat stress than WT plants, suggesting that SlMAPK3 was a negative regulator of thermotolerance. Moreover, antioxidant enzymes and HSPs/HSFs genes expression were involved in SlMAPK3-mediated heat stress response in tomato plants.
Highlights
High temperature is a major environmental stress that limits plant growth and agriculture productivity
On the contrary, when WT plants were exposed to higher temperature treatments (42 and 45 °C), the transcript levels of SlMAPK3 significantly reduced after heat treatment (Fig. 1d and e, P < 0.05)
The survival rate in slmapk3 mutants were 3.17 and 4.17 times higher than that in WT plants (Additional file 1: Figure S1). These results indicated that knockout of SlMAPK3 enhanced heat tolerance in tomato plants, suggesting that SlMAPK3 played a negative role in response to heat stress
Summary
High temperature is a major environmental stress that limits plant growth and agriculture productivity. Mitogen-activated protein kinases (MAPKs) are highly conserved serine and threonine protein kinases that participate in response to diverse environmental stresses in plants. Tomato (Solanum lycopersicum) is a globally popular horticultural commodity with great economic importance, which functions as a model plant species widely used in plant science, since it shows highly susceptible to diverse environmental stresses, such as drought, salinity, chilling, and heat. Mitogen activated protein kinase (MAPK) cascade have been reported to participate in signal transduction including plant development, hormone regulation, disease resistance, and stress responses [3]. There is increasing evidence that MAPK cascades play a vital role in mediating diverse cellular signaling network by transmitting extracellular stimuli to intracellular responses, which positively regulates gene expression and protein functions under various abiotic stresses, resulting in adaptive responses to environmental stresses [4]. Previous studies reported that MAPK genes expression are significantly induced in response to heat treatment [5], and AtMAPK6 in Arabidopsis thaliana [6], ZmMAPK1 in maize [7], MnMAPK1 in Mulberry [8], and
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