Abstract
Harsh environmental factors have continuous negative effects on plant growth and development, leading to metabolic disruption and reduced plant productivity and quality. However, filamentation temperature-sensitive H protease (FtsH) plays a prominent role in helping plants to cope with these negative impacts. In the current study, we examined the transcriptional regulation of the CaFtsH06 gene in the R9 thermo-tolerant pepper (Capsicum annuum L.) line. The results of qRT-PCR revealed that CaFtsH06 expression was rapidly induced by abiotic stress treatments, including heat, salt, and drought. The CaFtsH06 protein was localized to the mitochondria and cell membrane. Additionally, silencing CaFtsH06 increased the accumulation of malonaldehyde content, conductivity, hydrogen peroxide (H2O2) content, and the activity levels of superoxide dismutase and superoxide (·O2−), while total chlorophyll content decreased under these abiotic stresses. Furthermore, CaFtsH06 ectopic expression enhanced tolerance to heat, salt, and drought stresses, thus decreasing malondialdehyde, proline, H2O2, and ·O2− contents while superoxide dismutase activity and total chlorophyll content were increased in transgenic Arabidopsis. Similarly, the expression levels of other defense-related genes were much higher in the transgenic ectopic expression lines than WT plants. These results suggest that CaFtsH06 confers abiotic stress tolerance in peppers by interfering with the physiological indices through reducing the accumulation of reactive oxygen species, inducing the activities of stress-related enzymes and regulating the transcription of defense-related genes, among other mechanisms. The results of this study suggest that CaFtsH06 plays a very crucial role in the defense mechanisms of pepper plants to unfavorable environmental conditions and its regulatory network with other CaFtsH genes should be examined across variable environments.
Highlights
As sessile organisms, plants endure limitations to their growth, development, and agricultural productivity caused by abiotic stresses such as drought, salinity, and high temperatures [1,2,3]
We found that the green fluorescence signal of pVBG2307:CaFtsH06:GFP was detected in the tobacco leaf mitochondria and cell membrane, while the fluorescence of pVBG2307:GFP was distributed throughout the cell, indicating that CaFtsH06 protein in pepper may play a role in the mitochondria and cell membrane (Figure 4)
We found that the CaFtsH06 gene expression in the two lines of OE7 and OE9 under normal growth conditions was higher and that the leaf area of the transgenic lines was significantly larger than that of WT plants (Figure S4), in addition to their more vigorous phenotype after heat-stress treatment at 45 ◦C for 16 h
Summary
Plants endure limitations to their growth, development, and agricultural productivity caused by abiotic stresses such as drought, salinity, and high temperatures [1,2,3]. Plants have a number of defense mechanisms enabling their long-term acclimation to adverse environmental conditions, such as changes in the levels of phytohormones and Ca2+ content as well as reactive oxygen species (ROS) signaling and plant-programmed cell death (PCD) [6,7]. Through the restoration and hydrolysis of protein regulation systems, these defense mechanisms work together to repair functional failure proteins to maintain normal metabolic mechanisms [9]. FtsH protease activity can degrade misfolded and mistranslated proteins and provide a control mechanism to remove dysfunctional proteins in cells as central elements of energy metabolic control systems [14,15]
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