Study of the physiological mechanism of delaying cucumber senescence by wheat intercropping pattern

Promotion of faba bean seedling growth under Fusarium oxysporum f. sp. fabae and cinnamic acid stress in faba bean-wheat intercropping system and underlying proteomic mechanisms

Continuous cropping severely affects faba bean growth, mainly due to pathogen and autotoxic substance accumulation. Here, we used faba bean monocropping (M) and intercropping with wheat (I), with stress treatments of Fusarium oxysporum f. sp. fabae (FOF) alone (F) and combined with cinnamic acid (F + C), to analyze seedling growth, defense-related enzymes, levels of resistance-associated substances, and protein expression profiles in roots. The results showed that intercropping mitigated the inhibitory effects of FOF and cinnamic acid. FOF resulted in increased activities of defense-related enzymes as well as levels of resistance-associated substances. Proteomic analysis showed that 22 proteins were upregulated following FOF inoculation (M + F), and 6 proteins were downregulated after the addition of cinnamic acid (M + F + C) in monocropping plants; these proteins were mainly involved in pathways associated with carbohydrate metabolism, energy, and the cytoplasm. Comparison of monocropping and intercropping indicated that the upregulated proteins were mostly associated with stress and defense, carbohydrate transport and metabolism, maintenance of cellular homeostasis, and protein synthesis. KEGG analysis revealed that intercropping increased enrichment in pathways associated with metabolism, ribosomes, biosynthesis of secondary metabolites, proteasomes, pyruvate metabolism, and pentose and glucuronate interconversions. The results indicated that intercropping mitigated growth inhibition by FOF and cinnamic acid by increasing energy production, maintaining normal cellular functions, and promoting the synthesis of defense-associated secondary metabolites. These findings provide a basis for further investigation into the molecular mechanisms underlying the effects of intercropping in controlling resistance to Fusarium wilt in the faba bean.

Intercropping affects the physiology and cadmium absorption of pakchoi, lettuce, and radish seedlings

Intercropping can affect the growth and elemental absorption of vegetables. This study investigated the physiology and cadmium (Cd) content of pakchoi (Brassica chinensis L.), lettuce (Lactuca sativa L. var. ramosa Hort.), and radish (Raphanus sativus L.) seedlings under monoculture, mutual intercropping of two or three varieties. Intercropping is not conducive to the accumulation of chlorophyll and biomass content of pakchoi, lettuce, and radish. When three seedlings were intercropped together, the antioxidant enzyme activity of pakchoi, lettuce, and radish increased and the content of malondialdehyde decreased, except that the superoxide dismutase activity of radish is inferior to the value of radish and pakchoi intercropping. Intercropping increased the soluble sugar and proline content in the lettuce seedlings, while those in the radish and lettuce seedlings reduced or had no significant effect. When intercropped with pakchoi and lettuce, the Cd content in the roots and shoots of pakchoi is higher and lower, respectively. At the same time, root or shoot bio-concentration factors also performed the same trend, and TF was the smallest and less than 1; however, the TF of lettuce is greater than 1. When intercropping with pakchoi or lettuce separately or together, it promoted the accumulation of Cd in radish root; when intercropping with pakchoi, the value of TF was the smallest. From the antioxidant system, the performance of the three seedlings intercropped together is better than the two; however, the accumulation of Cd shows the opposite trend, and the participation of cabbage in the intercropping is relatively conducive to reducing the Cd content in the edible parts.

Intercropping of wheat alleviates the adverse effects of phenolic acids on faba bean

After years of continuous cultivation of faba beans (Vicia faba L.), autotoxic substances accumulate in the soil, leading to a high incidence of Fusarium oxysporum (FOF) wilt. Faba bean-wheat intercropping is often used to alleviate these problems. The goal of this research was to explore the role of benzoic acid and cinnamic acid in promoting the occurrence of faba bean Fusarium wilt and the potential mechanism of faba bean-wheat intercropping to control the occurrence of this disease. We established a field experiment and a hydroponic experiment that involved the inoculation of FOF and the exploration of exogenous addition of cinnamic acid and benzoic acid at different concentrations, the effects on the degree of peroxidation, resistance system, and ultrastructure of faba bean roots. In addition, the antioxidative response of faba bean-wheat intercropping against the autotoxicity of benzoic acid and cinnamic acid was examined. In the field experiment, compared with monoculture, faba bean-wheat intercropping effectively controlled the occurrence of Fusarium wilt, significantly reduced the contents of H₂O₂ and O₂ ^- in faba bean roots, increased the expression and activity of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), maintained cell stability, and significantly reduced the contents of benzoic acid and cinnamic acid in faba bean rhizosphere. In the pot experiment, it was found that compared with the control, different concentrations of benzoic acid and cinnamic acid (50, 100, and 200 mg·L^-1) significantly increased the content of H₂O₂ and O₂ ^- in faba bean, decreased the activity and gene expression of antioxidant enzymes SOD and CAT, and damaged cell membrane structure. Furthermore, it promoted the occurrence of Fusarium wilt of faba bean. The faba bean-wheat intercropping alleviated the stress. Benzoic acid and cinnamic acid can increase the content of hydrogen peroxide and superoxide anions in faba bean plants, reduce the enzymatic activity and expression of antioxidant enzyme genes, damage the cell membrane structure, and promote the occurrence of faba bean Fusarium wilt. The faba bean-wheat intercropping can effectively alleviate the autotoxicity of benzoic acid and cinnamic acid and reduce the occurrence of faba bean Fusarium wilt.

Melatonin Positively Regulates Both Dark- and Age-Induced Leaf Senescence by Reducing ROS Accumulation and Modulating Abscisic Acid and Auxin Biosynthesis in Cucumber Plants

Melatonin (MT), as a signaling molecule, plays a vital role in regulating leaf senescence in plants. This study aimed to verify the antioxidant roles of MT in delaying dark- or age-induced leaf senescence of cucumber plants. The results showed that endogenous MT responds to darkness and overexpression of CsASMT, the key gene of MT synthesis, and delays leaf senescence stimulated by darkness, as manifested by significantly lower malonaldehyde (MDA) and reactive oxygen species (ROS) contents as well as higher activities and gene expression of antioxidant enzymes compared to the control. Moreover, MT suppressed both age- or dark-induced leaf senescence of cucumber, as evidenced by a decrease in senescence-related gene SAG20 and cell-death-related gene PDCD expression and ROS content and an increase in antioxidant capacity and chlorophyll biosynthesis compared with the H₂O-treated seedlings. Meanwhile, the suppression of age-induced leaf senescence by melatonin was also reflected by the reduction in abscisic acid (ABA) biosynthesis and signaling pathways as well as the promotion of auxin (IAA) biosynthesis and signaling pathways in cucumber plants in the solar greenhouse. Combining the results of the two separate experiments, we demonstrated that MT acts as a powerful antioxidant to alleviate leaf senescence by activating the antioxidant system and IAA synthesis and signaling while inhibiting ABA synthesis and signaling in cucumber plants.

Global analysis of lysine 2-hydroxyisobutyrylation in wheat root

Lysine 2-hydroxyisobutyrylation (Khib) is a novel naturally occurring post-translational modification. The system Khib identification at proteomics level has been performed in various species and tissues to characterize the role of Khib in biological activities. However, the study of Khib in plant species is relatively less. In the present study, the first plant root tissues lysine 2-hydroxyisobutyrylome analysis was performed in wheat with antibody immunoprecipitation affinity, high resolution mass spectrometry-based proteomics and bioinformatics analysis. In total, 6328 Khib sites in 2186 proteins were repeatedly identified in three replicates. These Khib proteins showed a wide subcellular location distribution. Function and pathways characterization of these Khib proteins indicated that many cellular functions and metabolism pathways were potentially affected by this modification. Protein and amino acid metabolism related process may be regulated by Khib, especially ribosome activities and proteins biosynthesis process. Carbohydrate metabolism and energy production related processes including glycolysis/gluconeogenesis, TCA cycle and oxidative phosphorylation pathways were also affected by Khib modification. Besides, root sulfur assimilation and transformation related enzymes exhibited Khib modification. Our work illustrated the potential regulation role of Khib in wheat root physiology and biology, which could be used as a useful reference for Khib study in plant root.