The contribution of Ca and Mg to the accumulation of amino acids in maize: from the response of physiological and biochemical processes.

BACKGROUND: The quality of maize kernels is significantly enhanced by amino acids, which are the fundamental building blocks of proteins. Meanwhile, calcium (Ca) and magnesium (Mg), as important nutrients for maize growth, are vital in regulating the metabolic pathways and enzyme activities of amino acid synthesis. Therefore, our study analyzed the response process and changes of amino acid content, endogenous hormone content, and antioxidant enzyme activity in kernels to the coupling addition of sugar alcohol-chelated Ca and Mg fertilizers with spraying on maize. RESULT: (1) The coupled addition of Ca and Mg fertilizers increased the Ca and Mg content, endogenous hormone components (indole-3-acetic acid, IAA; gibberellin, GA; zeatin riboside, ZR) content, antioxidant enzyme activity, and amino acid content of maize kernels. The content of Ca and Mg in kernels increased with the increasing levels of Ca and Mg fertilizers within a certain range from the filling to the wax ripening stage, and significantly positively correlated with antioxidant enzyme activities. (2) The contents of IAA, GA, and ZR continued to rise, and the activities of superoxide dismutase (SOD) and catalase (CAT) were elevated, which effectively enhanced the ability of cells to resist oxidative damage, promoted cell elongation and division, and facilitated the growth and development of maize. However, the malondialdehyde (MDA) content increased consistently, which would attack the defense system of the cell membrane plasma to some extent. (3) Leucine (LEU) exhibited the highest percentage of essential amino acid components and a gradual decline from the filling to the wax ripening stage, with the most substantial beneficial effect on essential amino acids. (4) CAT and SOD favorably governed essential amino acids, while IAA and MDA negatively regulated them. The dominant physiological driving pathway for the synthesis of essential amino acids was "IAA-CAT-LEU", in which IAA first negatively drove CAT activity, and CAT then advantageously controlled LEU synthesis. CONCLUSION: These findings provide a potential approach to the physiological and biochemical metabolism of amino acid synthesis, and the nutritional quality enhancement of maize kernel.

Competitive interactions between invasive fall armyworm and Asian corn borer at intraspecific and interspecific level on the same feeding guild.

Interspecific competition is an important factor in the population dynamics and geographical distribution of insect populations. Fall armyworm (FAW), Spodoptera frugiperda, an invasive species, and the Asian corn borer (ACB), Ostrinia furnacalis, a native pest species are major pests on maize in China, posing a threat to maize yield and grain quality. A series of laboratory, greenhouse, and field experiments were conducted to elucidate the competitive interactions between FAW and ACB. In the laboratory experiments, FAW exhibited aggressive behaviors more frequently when compared with ACB, while the latter species exhibited defense behaviors more frequently. Higher intraspecific competition was recorded in the FAW conspecific rather than in ACB, particularly in the 6th larval stage. FAW had a higher interspecific competitive advantage through intraguild predation over ACB, resulting in partial or complete displacement ACB when initially the ratio of the 2 species was 1 : 1. The interspecific competition also had significantly influenced on the population parameters, defensive enzymes, and nutrient of these 2 species. Competitive interaction proved that the response of superoxide, catalase, and soluble protein in FAW were significantly increased, whereas the total sugar content in both species was substantially decreased. Survival rate, and the plant damage that co-infested by both species varied significantly among the sequential combinations under greenhouse and field conditions. FAW consistently exhibited stronger intraspecific aggression than ACB under laboratory and field conditions when co-existing on the same feeding guild. These findings contribute to efforts toward the improvement of integrated pest management programs for FAW, in decision making for invasive and native pests' management strategies to reduce the high risks of FAW and ACB outbreaks.

Design, Synthesis, Antibacterial Activity, and Mechanism of Novel Mesoionic Compounds Based on Natural Pyrazole Isolated from an Endophytic Fungus Colletotrichum gloeosporioides.

Xanthomonas oryzae pv. oryzicola (Xoo) is a type of bacteria that causes bacterial leaf blight disease in rice plants. This disease is substantially harmful, and the current prevention and control measures are facing challenges. This study has investigated the effectiveness of the control activity that the endophytic fungus NS7 fermented from Dendrobium candidum possessed against Xoo. Twenty-eight novel mesoionic compounds were designed and synthesized based on the natural compound D. These compounds displayed moderate to excellent anti-Xoo activity in vitro. Notably, compound 24 exhibited prominent anti-Xoo activity in vitro with an EC50 value of 40.3 mg/L, which was better than that of the positive control thiodiazole copper (TC)(71.2 mg/L) and the lead compound D (108.1 mg/L). In vivo pot experiments on Xoo showed that compound 24 exhibited protective and curative activities of 39.4 and 30.4%, respectively, which were better than those of TC (35.7 and 28.8%, respectively). Further, a preliminary mechanism study indicated that compound 24 could enhance the activity of defense enzymes to improve the ability for anti-Xoo. Meanwhile, compound 24 could also regulate the carbon fixation in photosynthetic organisms, which might be related to the enhanced immune function of rice. This study offers a new strategy for discovering antibacterial agents based on natural products.

First Discovery of Imidazo[1,2-a]pyridine Mesoionic Compounds Incorporating a Sulfonamide Moiety as Antiviral Agents.

The applications of mesoionic compounds and their analogues as agents against plant viruses remain unexplored. This was the first evaluation of the antiviral activities of mesoionic compounds on this issue. Our study involved the design and synthesis of a series of novel imidazo[1,2-a]pyridine mesoionic compounds containing a sulfonamide moiety and the assessment of their antiviral activities against potato virus Y (PVY). Compound A33 was assessed on the basis of three-dimensional quantitative structure-activity relationship (3D-QSAR) model analysis and displayed good curative, protective, and inactivating activity effects against PVY at 500 mg/L, up to 51.0, 62.0, and 82.1%, respectively, which were higher than those of commercial ningnanmycin (NNM, at 47.2, 50.1, and 81.4%). Significantly, defensive enzyme activities and proteomics results showed that compound A33 could enhance the defense response by activating the activity of defense enzymes, inducing the glycolysis/gluconeogenesis pathway of tobacco to resist PVY infection. Therefore, our study indicates that compound A33 could be applied as a potential viral inhibitor.

Design, Synthesis, Anti-Tomato Spotted Wilt Virus Activity, and Mechanism of Action of Thienopyrimidine-Containing Dithioacetal Derivatives.

Currently, there is insufficient viricide to effectively control tomato spotted wilt virus (TSWV). To address this pending issue, a series of thienopyrimidine-containing dithioacetal derivatives were prepared and tested for their anti-TSWV activities. A subsequent three-dimensional quantitative structure-activity relationship was constructed to indicate the development of optimal compound 35. The obtained compound 35 had excellent anti-TSWV curative, protective, and inactivating activities (63.0, 56.6, and 74.1%, respectively), and the EC50 values of protective and inactivating activities of compound 35 were 252.8 and 113.5 mg/L, respectively, better than those of ningnanmycin (284.8 and 144.7 mg/L) and xiangcaoliusuobingmi (624.9 and 300.0 mg/L). In addition, the anti-TSWV activity of compound 35 was associated with defense-related enzyme activities, enhanced photosynthesis, and reduced stress response, thereby enhancing disease resistance.

Discovery of Novel Benzo[4,5]thiazolo(oxazolo)[3,2-a]pyrimidinone Mesoionic Derivatives as Potential Antibacterial Agents and Mechanism Research.

A series of benzo[4,5]thiazole(oxazole)[3,2-a]pyrimidine mesoionic compounds were designed and synthesized. Antibacterial activity tests revealed that compound A23 showed good in vitro activities against Xanthomonas oryzae pv. Oryzicola (Xoc) and Xanthomonas oryzae pv. oryzae (Xoo), with half-maximal effective concentration (EC50) values of 47.6 and 36.8 µM, respectively, which were better than positive control agents thiodiazole copper (281 and 259 µM) and bismerthiazol (245 and 220 µM). The protective activities of compound A23 anti-Xoc and anti-Xoo were 39.7% and 49.2%, respectively, which were better than those of bismerthiazol (31.5% and 40.7%). Compound A23 improved defensive enzyme activities in rice. In addition, compound A23 could upregulate the expression of succinate dehydrogenase (SDH) in the oxidative phosphorylation (OXPHOS) pathway through proteomics analysis, which was consistent with the result of the SDH activity test. Thus, compound A23 is a novel potential antibacterial agent that can be further developed.

Design, synthesis and anti-TMV activity of novel α-aminophosphonate derivatives containing a chalcone moiety that induce resistance against plant disease and target the TMV coat protein.

Plant viral diseases, known as "plant cancer", with high contagiosity can substantially reduce crop quality and yield. To identify potential anti-tobacco mosaic virus (TMV) agents with different mechanisms, a series of novel α-aminophosphonate derivatives containing a chalcone moiety were designed and synthesized. Bioassay results revealed that some target compounds exhibited improved curative activity against TMV in vivo, and the EC50 value of compound B3 was 356.7 mg L-1. The activities of the defensive enzymes POD and CAT from tobacco leaves treated with B3 and B17 showed that these target compounds could improve the photosynthetic ability of the leaves and activate plant host resistance against TMV infection. The binding constant between B3 and TMV Coat Protein (CP) (2.51 × 108 M-1), calculated by the fluorescence titration experiment and docking results, revealed that B3 has a strong interaction with TMV CP. Further docking analysis revealed that B3 was embedded between two layers of the TMV CP, which was consistent with the 2:1 binding mode of TMV CP and B3 determined by the binding affinity experiment. The TEM morphological study of TMV treated with B3 and B17 indicated that this series of target compounds may trigger the disassembly of TMV by interacting directly with TMV CP. This study provides new insight for the discovery of antiviral compounds with two different mechanisms of action.

[Biocontrol effect and mechanism of Bacillus laterosporus Bl13 against early blight disease of tomato]. / 侧孢芽孢杆菌Bl13å¯¹ç•ªèŒ„æ—©ç–«ç— é˜²æ²»æ•ˆæžœåŠæœºåˆ¶.

Bacillus laterosporus Bl13 has good antagonistic effect on the pathogen of tomato early blight (TEB) disease. A pot experiment was conducted to investigate the effect and mechanism of B. laterosporus Bl13 against TEB disease by measuring biological traits such as plant height, stem diameter, disease index of TEB, activity of plant defense enzyme in leaves, and microbial diversity and community composition in root area. The results showed that B. laterosporus Bl13 could significantly reduce the disease index of TEB disease incidence, increase the activity of defensive enzymes including polyphenol oxidase (PPO) and peroxidase (POD) in leaves, and reduce the effects of the disease on the aboveground and root growth of tomato. Meanwhile, B. laterosporus Bl13 improved soil microbial community structure in the root zone, by significantly increasing the relative abundance of plant growth-promoting bacteria (Bacillus and Pseudomonas) and decreasing that of Olpidium and Haematonectria. The results showed that B. laterosporus Bl13 could enhance plant resistance against TEB disease through improving the activity of defensive enzymes in tomato leaves and increasing the number of beneficial microbes in the root zone.

Plant Defense Responses Induced by Two Herbivores and Consequences for Whitefly Bemisia tabaci.

Diverse herbivores are known to induce various plant defenses. The plant defenses may detrimentally affect the performance and preference to subsequent herbivores on the same plant, such as affecting another insect's feeding, settling, growth or oviposition. Here, we report two herbivores (mealybug Phenacoccus solenopsis and carmine spider mite Tetranychus cinnabarinus) which were used to pre-infest the cucumber to explore the impact on the plants and the later-colonizing species, whitefly Bemisia tabaci. The results showed that the whiteflies tended to select the treatments pre-infested by the mites, rather than the uninfected treatments. However, the result of treatments pre-infested by the mealybugs was opposite. Total number of eggs laid of whiteflies was related to their feeding preference. The results also showed that T. cinnabarinus were more likely to activate plant jasmonic acid (JA) regulated genes, while mealybugs were more likely to activate key genes regulated by salicylic acid (SA). The different plant defense activities on cucumbers may be one of the essential factors that affects the preference of B. tabaci. Moreover, the digestive enzymes and protective enzymes of the whitefly might play a substantial regulatory role in its settling and oviposition ability.

Physiological Responses Induced by Ostrinia furnacalis (Lepidoptera: Crambidae) Feeding in Maize and Their Effects on O. furnacalis Performance.

λ: Plants damaged by herbivorous insects often respond by mounting a series of defense responses that can inhibit the insect's fitness. Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae) is a major insect pest in maize throughout much of Asia, Australia, and the western Pacific islands. We examined the effects of O. furnacalis -induced maize defenses on O. furnacalis fitness, and explained the effects from biochemical changes that occur in maize leaves in response to O. furnacalis feeding. The results of the age-stage, two-sex life table showed that significantly longer larval and pupal life spans, and total preoviposition period (TPOP) occurred. A decrease in the longevity and fecundity of female adults was observed in O. furnacalis fed on O. furnacalis -damaged leaves. The mean generation time ( T ), finite rate of increase ( ), net reproductive rate ( R 0 ), and intrinsic rate of increase ( r ) were also correspondingly affected. Biochemical assays indicated that 24 h of O. furnacalis herbivory resulted in decreased levels of the benzoxazinoids, 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), and 2-(2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one)-ß-D-glucopyranose (DIMBOA-Glc), and a corresponding increase in 2-(2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one)-ß-D-glucopyranose (HDMBOA-Glc). Maize also exhibited higher activities of the defensive enzymes-peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and polyphenol oxidase (PPO)-after 24 h of herbivory. We concluded that exposure to O. furnacalis -damaged leaves had an inhibitory impact on the fitness of the neonate to pupa stages of O. furnacalis . The observed higher level of HDMBOA-Glc and higher enzymatic activities of POD, SOD, CAT, and PPO may account, in part, for the observed inhibitory effects on O. furnacalis fitness.

The Effect and Action Mechanisms of Oligochitosan on Control of Stem Dry Rot of Zanthoxylum bungeanum.

In this report, the effects of two oligochitosans, i.e., oligochitosan A (OCHA) and oligochitosan B (OCHB), on control of dry rot of Zanthoxylum bungeanum (Z. bungeanum) caused by Fusarium sambucinum (F. sambucinum) were evaluated. First, both oligochitosans show desirable ability to decrease the infection of F. sambucinum. Second, the oligochitosans strongly inhibit the radial colony and submerged biomass growth of F. sambucinum. Lastly, these oligochitosans are capable of increasing the activities of phenylalanine ammonia lyase (PAL), polyphenoloxidase (PPO) and peroxidase (POD) significantly, as well as enhancing the content of total phenolics in Z. bungeanum stems. These findings indicate that the protective effects of OCHA and OCHB on Z. bungeanum stems against dry rot may be associated with the direct fungitoxic function against pathogen and the elicitation of biochemical defensive responses in Z. bungeanum stems. The outcome of this report suggests that oligochitosans may serve as a promising natural fungicide to substitute, at least partially, for synthetic fungicides in the disease management of Z. bungeanum.