| In recent years, frequent extreme weather conditions often affect vegetable production, particularly with the greenhouse effect phenomenon and the abuse of the environment through human activities. Chilling injury which usually occur during winter and spring seasons in north of China are also on the increase. The situation posses a great challenge to the production and supply of vegetables. Therefore, analyzing the mechanism of plant in response to stress, and using molecular genetics, physiology and biochemistry, and environmental regulation to improve resistance to adverse environmental conditions in vegetable crops have very significant sense to improve vegetable production, quality and economic benefit, and to promote sustainable agriculture. Brassinosteroids(BRs) are a group of steroid phytohormones that have high bioactivity and have been found to influence diverse physiological processes in plants. They also play a significant role in the amelioration of various biotic and abiotic stresses. However, these results do not necessarily mean that BRs have a direct role in the regulation of abiotic stresses.In this study, we used pepper(Capsicum annuum L.cv.‘Xiangyan NO.16’) seedlings to investigate the effect of exogenous 24-epibrassinolide(EBR) on the growth, chlorophyll fluorescence characteristics, distribution of absorbed energy and excitation energy, lipid peroxidation and antioxidant defense system of pepper seedlings under chilling stress. Additonnally, we used RNA-seq and i TRAQ method to carry out transcriptome and proteomics analysis of pepper to reveal the role of 24-epibrassinolide in response to chilling. The main results were as follows:Different EBR concentrations(0, 10 μΜ, 1 μM, 0.1 μM, 0.01 μM, 0.001 μM) were applied to the seedling by foliar spray under chilling stress. Chilling stress inhibited the root growth of pepper seedlings, whereas EBR alleviated the inhibitory effect of chilling stress via regulating the total root length, root surface area and number of root forks in seedling roots. EBR treatment significantly promoted SOD, POD and CAT activities, and decreased the contents of MDA under chilling stress. The results showed that EBR alleviated oxidative damage of seedling roots and the tolerance of plants under chilling stress. We found that 0.1 μM of EBR was the optimum concentration suitable for chill-seedlings.The results showed that chilling stress inhibited the growth of pepper seedlings, but the foliar spray of EBR solution markedly improved the photoinhibition by increasing maximum quantum efficiency of PSII(Fv/Fm), the actual photochemical efficiency of PSII(ΦPSII), photochemical quenching coefficient(q P) and the efficiency of excitation capture of open PSII center(Fv’/Fm’). Likewise, EBR increased the fraction of photochemical efficiency(P) and reduced the fraction of antenna heat dissipation(D) and excess energy(E). Increased accumulation of H2O2, O2- and OH-, accompanied with high lipid peroxidation confirmed the occurrence of oxidative stress under low temperature. The activities of antioxidative enzymes such as superoxide dismutase(SOD), peroxidase(POD), catalase and ascorbate peroxidase(CAT), and contents of ascorbic acid(As A) and reduced glutathione(GSH) were significantly increased by EBR during low-temperature stress. The EBR treatment also greatly enhanced contents of proline, soluble sugar and protein under chilling stress. EBR significantly decreased harmful reactive oxygen species(ROS) accumulation and lipid peroxidation through the induction of antioxidant defense system. Our results suggest that EBR has an anti-stress effect on pepper seedlings against chilling stress that may strengthen phytoremediation approaches by enhancing plant tolerance.In this study, we used RNA sequencing technique to observe a positive regulation of 24-epibrassinolide(EBR) response to chilling stress in pepper. In both EBR treatment(Chill+EBR) and control(Chill) samples had 39,829 transcript files. Among these, 656 genes were significantly differently expressed genes(DEGs) in EBR-treated pepper seedlings versus controls, including 335 up-regulated and 321 down-regulated DEGs. We selected randomly 20 genes of DEGs for RT-q PCR analysis to confirm their changes from RNA-Seq. Based on gene ontology enrich and KEGG pathway analysis, we found that photosynthesis was significantly up-enriched in biological processes. In addition, BRs induced cellulose synthase-like protein and UDP-glycosyltransferase, contributing to formation of the cell wall and hormone metabolism. BRs also triggered the calcium signaling transduction in cytoplasm, and transmitted to the downstream effectors to activate the expression of cellular redox homeostasis related genes, such as GSTX1, PER72, and CAT2. We identified genes associated with hormone metabolism, redox, signaling and defense, and they showed different expression patterns under EBR-treatment. Overall, we provide the first transcripts study of BRs responses to chilling stress in pepper, and transcriptome analysis also revealed an available theoretical basis and novel gene resources for research resistance to low temperature.We used the i TRAQ method to analyse the leaf proteomes with or without 0.1 μM EBR-treatment under chilling stress for 7 days. A total of 4,661 proteins were identified in the pepper seedlings. After differential screening, we identified 346 different expression proteins, including 217 up-regulated proteins and 129 down-regulated proteins. Based on gene ontology enrich analysis, we found that cell function and cell component related proteins were significantly up-enriched in cellular component. The proteins related to metabolic process, cellular process and response to stimulus related were significantly up-enriched in biological process; and catalytic activity, binding, structural molecular activity and antioxidant activity related proteins were significantly up-enriched in molecular function. Based on KEGG pathway analysis, we found that differently expressed proteins were significantly enriched in 82 pathways, mainly including metabolic pathways, biosynthesis of secondary metabolites, nucleoprotein and photosynthesis-antenna proteins. These proteins were mainly involved in the formation of light harvest complex, photosystem II, photosynthetic electron transfer chain, and photosystem I, energy metabolism, Calvin cycle, photosynthetic pigment metabolism, metabolism, stress and defence, transcription, protein synthesis, as well as signaling transduction. |
PDF Full Text Request