Abstract
Brassinosteroids (BRs) are important in plant resistance to chilling stress. However, limited information is available regarding the specific mechanisms involved at proteomic level. We utilized the iTRAQ proteomic approach, physiological assays and information obtained from cellular ultrastructure to clarify the underlying molecular mechanism of BRs to alleviate chilling stress in pepper (Capsicum annuum L.). Foliar application of 24-epibrassinolide (EBR) improved photosynthesis and improved cell structure by presenting a distinct mesophyll cell and chloroplast with well-developed thylakoid membranes in the leaves of pepper seedlings. We identified 346 differentially expressed proteins (DEPs), including 217 up-regulated proteins and 129 down-regulated proteins in plants under chilling (Chill) and Chill + EBR treated plants. Most of the DEPs were related to multiple pathways, including photosynthesis, carbohydrate metabolism, energy metabolism, protein biosynthesis, amino acid synthesis, redox and stress defence (ascorbate peroxidase, glutathione peroxidase and superoxide dismutase). Up-regulated DEPs were associated with the photosynthetic electron transfer chain, oxidative phosphorylation, GSH metabolism pathway, Calvin cycle and signaling pathway. The physiochemical analysis showed that EBR treatment improved the tolerance of pepper seedlings to chilling stress.
Highlights
Chilling is an abiotic stress which impairs plant development, fruit yield, and quality (Zhang et al 2021)
This study provides valuable information regarding the mechanism of BRs to improve chilling stress tolerance of pepper seedlings, and this can be useful for the plant biologist interested to study the mechanisms of BRs to improve stress tolerance under other kinds of abiotic stresses
We found that EBR could down-regulate the protein associated with the cell wall's ductility for sustaining cell integrity under chilling stress conditions
Summary
Chilling is an abiotic stress which impairs plant development, fruit yield, and quality (Zhang et al 2021). Some previous studies related to BRs-induced chilling stress amelioration highlights the role of BRs at the physiological, biochemical and genetic levels (Liu et al 2011; Gao et al 2015). In our previous study, we reported that BRs application could alleviate the damage caused by excessive light and decreased ROS accumulation in pepper seedlings under low-temperature stress (Li et al 2015). These findings enhance our understanding of BRs responses and chilling-induced stress in plants, some questions remain unanswered, such as plants proteomic responses to chilling stress
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