Abstract
Pepper is a typical warmth-loving vegetable that lacks a cold acclimation mechanism and is sensitive to cold stress. Lysine acetylation plays an important role in diverse cellular processes, but limited knowledge is available regarding acetylation modifications in the resistance of pepper plants to cold stress. In this study, the proteome and acetylome of two pepper varieties with different levels of cold resistance were investigated by subjecting them to cold treatments of varying durations followed by recovery periods. In total, 6,213 proteins and 4,574 lysine acetylation sites were identified, and this resulted in the discovery of 3,008 differentially expressed proteins and 768 differentially expressed acetylated proteins. A total of 1,988 proteins were identified in both the proteome and acetylome, and the functional differences in these co-identified proteins were elucidated through GO enrichment. KEGG analysis showed that 397 identified acetylated proteins were involved in 93 different metabolic pathways. The dynamic changes in the acetylated proteins in photosynthesis and the “carbon fixation in the photosynthetic organisms” pathway in pepper under low-temperature stress were further analyzed. It was found that acetylation of the PsbO and PsbR proteins in photosystem II and the PsaN protein in photosystem I could regulate the response of pepper leaves to cold stress. The acetylation levels of key carbon assimilation enzymes, such as ribulose bisphosphate carboxylase, fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase, glyceraldehyde 3-phosphate dehydrogenase, phosphoribulokinase, and triosephosphate isomerase decreased, leading to decreases in carbon assimilation capacity and photosynthetic efficiency, reducing the cold tolerance of pepper leaves. This study is the first to identify the acetylome in pepper, and it greatly expands the catalog of lysine acetylation substrates and sites in Solanaceae crops, providing new insights for posttranslational modification studies.
Highlights
Pepper (Capsicum annuum L.) is one of the most important vegetable crops in the world, and it is regarded as being a good source of basic nutrients, including capsaicinoids, pigments, and vitamins (Aza-González et al, 2011)
It was found that injury to A188 under cold stress appeared later and the plant recovered more while the damage under cold stress to A122 appeared earlier, and it was difficult for the plant to recover (Figures 1A,B and Supplementary Figure 1)
Malonaldehyde reflects oxidative injury of membranes; soluble sugars are important osmotic regulatory substances in plants, especially under cold stress; changes in relative water content probably reflect the degree of stress, whereas glutathione reductase activity is an enzyme involved in protection from oxidative stress, which usually accompanies cold stress
Summary
Pepper (Capsicum annuum L.) is one of the most important vegetable crops in the world, and it is regarded as being a good source of basic nutrients, including capsaicinoids, pigments (anthocyanins and carotenoids), and vitamins (Aza-González et al, 2011). It is a typical warmth-loving vegetable that lacks a cold acclimation mechanism and is sensitive to cold stress; the optimal temperature range for its growth is 21–28◦C. Using twodimensional differential in-gel electrophoresis, Kosová et al (2013) identified 36 DEPs in spring and winter wheat under cold stress; they found an increased abundance of proteins involved in carbohydrate catabolism, redox metabolism, and chaperones, as well as defense-related proteins
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