Physiological and quantitative proteomic analysis of NtPRX63-overexpressing tobacco plants revealed that NtPRX63 functions in plant salt resistance.

High salinity is harmful to crop yield and productivity. Peroxidases (PRXs) play crucial roles in H2O2 scavenging. In our previous study, PRX63 significantly upregulated in tobacco plants under salt stress. Thus, in order to understand the function of PRX63 in tobacco salt response, we overexpressed this gene in tobacco (Nicotiana tabacum L.), investigated the morphological, physiological and proteomic profiles of NtPRX63-overexpressing tobacco transgenic lines and wild type. The results showed that, compared with the wild type, the transgenic tobacco plants presented enhanced salt tolerance and displayed lower ROS (reactive oxygen species), malondialdehyde (MDA) and Na+ contents; higher biomass, potassium content, soluble sugar content, and peroxidase activity; and higher expression levels of NtSOD, NtPOD and NtCAT. Protein abundance analysis revealed 123 differentially expressed proteins between the transgenic and wild-type plants. These proteins were functionally classified into 18 categories and are involved in 41 metabolic pathways. Furthermore, among the 123 proteins, eight proteins involved in the ROS-scavenging system, 12 involved in photosynthesis and energy metabolism processes, two stress response proteins, one signal transduction protein and one disulfide isomerase were significantly upregulated. Furthermore, three novel proteins that may be involved in the plant salt response were also identified. The results of our study indicate that an enhanced ROS-scavenging ability, together with the expression of proteins related to energy mobilization and the stress response, functions in the confirmed salt resistance of transgenic tobacco plants. Our data provide valuable information for research on the function of NtPRX63 in tobacco in response to abiotic stress.

Quantitative Proteomic Analysis of Alligator Weed Leaves Reveals That Cationic Peroxidase 1 Plays Vital Roles in the Potassium Deficiency Stress Response.

Alligator weed is reported to have a strong ability to adapt to potassium deficiency (LK) stress. Leaves are the primary organs responsible for photosynthesis of plants. However, quantitative proteomic changes in alligator weed leaves in response to LK stress are largely unknown. In this study, we investigated the physiological and proteomic changes in leaves of alligator weed under LK stress. We found that chloroplast and mesophyll cell contents in palisade tissue increased, and that the total chlorophyll content, superoxide dismutase (SOD) activity and net photosynthetic rate (PN) increased after 15 day of LK treatment, but the soluble protein content decreased. Quantitative proteomic analysis suggested that a total of 119 proteins were differentially abundant proteins (DAPs). KEGG analysis suggested that most represented DAPs were associated with secondary metabolism, the stress response, photosynthesis, protein synthesis, and degradation pathway. The proteomic results were verified using parallel reaction monitoring mass spectrometry (PRM-MS) analysis and quantitative real-time PCR (qRT-PCR)assays. Additional research suggested that overexpression of cationic peroxidase 1 of alligator weed (ApCPX1) in tobacco increased LK tolerance. The seed germination rate, peroxidase (POD) activity, and K+ content increased, and the hydrogen peroxide (H2O2) content decreased in the three transgenic tobacco lines after LK stress. The number of root hairs of the transgenic line was significantly higher than that of WT, and net K efflux rates were severely decreased in the transgenic line under LK stress. These results confirmed that ApCPX1 played positive roles in low-K+ signal sensing. These results provide valuable information on the adaptive mechanisms in leaves of alligator weed under LK stress and will help identify vital functional genes to apply to the molecular breeding of LK-tolerant plants in the future.

Comparative Morphology, Transcription, and Proteomics Study Revealing the Key Molecular Mechanism of Camphor on the Potato Tuber Sprouting Effect.

Sprouting regulation in potato tubers is important for improving commercial value and producing new plants. Camphor shows flexible inhibition of tuber sprouting and prolongs the storage period of potato, but its underlying mechanism remains unknown. The results of the present study suggest that camphor inhibition caused bud growth deformities and necrosis, but after moving to more ventilated conditions, new sprouts grew from the bud eye of the tuber. Subsequently, the sucrose and fructose contents as well as polyphenol oxidase (PPO) activity were assessed after camphor inhibition. Transcription and proteomics data from dormancy (D), sprouting (S), camphor inhibition (C), and recovery sprouting (R) samples showed changes in the expression levels of approximately 4000 transcripts, and 700 proteins showed different abundances. KEGG (Kyoto encyclopaedia of genes and genomes) pathway analysis of the transcription levels indicated that phytohormone synthesis and signal transduction play important roles in tuber sprouting. Camphor inhibited these processes, particularly for gibberellic acid, brassinosteroids, and ethylene, leading to dysregulation of physiological processes such as cutin, suberine and wax biosynthesis, fatty acid elongation, phenylpropanoid biosynthesis, and starch and sucrose metabolism, resulting in bud necrosis and prolonged storage periods. The KEGG pathway correlation between transcripts and proteins revealed that terpenoid backbone biosynthesis and plant-pathogen interaction pathways showed significant differences in D vs. S samples, but 13 pathways were remarkably different in the D vs. C groups, as camphor inhibition significantly increased both the transcription levels and protein abundance of pathogenesis-related protein PR-10a (or STH-2), the pathogenesis-related P2-like precursor protein, and the kirola-like protein as compared to sprouting. In recovery sprouting, these genes and proteins were decreased at both the transcriptional level and in protein abundance. It was important to find that the inhibitory effect of camphor on potato tuber sprout was reversible, revealing the action mechanism was similar to resistance to pathogen infection. The present study provides a theoretical basis for the application of camphor in prolonging seed potato storage.