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Soil quality is an important determinant of soil-use efficiency in the Loess Plateau. However, there is no in-depth study on the soil quality of the Loess Plateau. The present study compared the quality of the 0–20 cm soil layer (T0-20) and the 20–40 cm soil layer (T20-40) from the Guyuan region located in the Loess Plateau. The analysis revealed that T0-20 had a higher content of total N, total P, available P, and organic matter, and the activities of microbial enzymes, especially β-grape-glycosidase (β-GC) and sucrase (SC), than T20-40, indicating that soil quality in T0-20 was better than T20-40. Amplicon sequencing found that Pseudombrophila from Ascomycota was the most abundant microbial species and significantly differed between T0-20 (34.2%) and T20-40 (48.7%). This species and another 19 microbial species, such as Ceratobasidiaceae and Mortierellaceae, determined the diversity of soil microorganism. Further analysis of the phenotype and other parameters of pepper seedlings subjected to P. capsici infection isolated from test soil revealed that decreased organic matter content in deep soil layer is related to happening of pepper blight, and 3 h after infection was the critical time point for infection. The peroxidase (POD) activity increased after P. capsici infection and was positively correlated with infection time, suggesting this enzyme may be an indicator of pepper blight occurrence. These findings provide a theoretical foundation for planning pepper blight management and crop cultivation strategies in the Guyuan region. [ABSTRACT FROM AUTHOR]

Highlights • CaHSP22.0 was expressed in different tissues of pepper plants. • Silence of CaHSP22.0 conferred peppers more sensitivity to high temperature and salt stress. • Overexpression of CaHSP22.0 did not enhance pepper resistance to high temperature and salt stress. Abstract Small heat shock proteins (sHSPs) are ubiquitous and diverse molecular chaperones. However, the contribution of sHSPs in pepper response to stress is controversial. In the study, we characterized a small heat shock protein gene CaHSP22.0 from pepper sHSP20s family, and found that the deduced amino acid sequence of CaHSP22.0 gene contained the conserved necessary domains and residue for sHSPs functions. Under normal condition, CaHSP22.0 was detected in all pepper organs, but its transcript level was up-regulated under high temperature and salt stress. CaHSP22.0-silenced pepper exhibits more sensitive to heat and salt stress, which was primarily reflected by aggravated chlorophyll degradation, increased leaf conductivity, level of superoxide anion free radical and malondialdehyde content. Interestingly, CaHSP22.0 overexpression also resulted in Arabidopsis sensitivity to high temperature and salt stress by inhibiting normal growth of leaves and roots, increasing superoxide anion free radical, decreasing activities of antioxidant enzymes and chlorophyll content, increasing malondialdehyde content, and disturbing low expression of genes involved in environment stress. Our results suggested that modified expression of CaHSP22.0 conferred peppers more sensitivity to high temperature and salt stress. The possible mechanism for CaHSP22.0 silencing is speculated to the damage to cell membrane; as for gene over-expression, the mechanism was complexed and might be the disruption of ROS caused by the improper levels of CaHSP22.0 with its substrates. [ABSTRACT FROM AUTHOR]

Pigments are important in vegetable kingdom. However, little is known regarding role of their combination in pepper. In this study, three pepper strains were crossed to get F1 pepper plants, and exposed to whitefly attack at 6–8 leaves stage. Populations (M1–M9) differing in leaf color divulged that leaf color inherited to progenies at different extent and intensively showed matrocliny. Furthermore, in purple-colored population, the accumulation of anthocyanin improved the physiology and resistance to whitefly, with increased photosynthetic rate (Pn), Fv/Fm as well as root activity and reduction in superoxide dismutase (SOD), peroxidase (POD), malonaldehyde (MDA) and pest index (PI). Best manifestation of these parameters was observed in M3 population, indicating plant development be related to the optimum combination of anthocyanin and chlorophyll in the investigated leaves. Interestingly, M3 population possessed highest resistance to whitefly, while level of its anthocyanin and chlorophyll was in moderate level. Besides, no significant difference was observed in the expression levels of genes related to carotenoid metabolism in all populations. significant correlation was observed between PI and expression of genes related to pigment, namely CaGLK and CaCHS genes (R2 > 0.8), while the correlation was also found between ANS and GUN 4 genes. These results suggested that the combination of anthocyanin and chlorophyll could enhance the resistance of pepper plants against whitefly attack. [ABSTRACT FROM AUTHOR]

A novel phase shifter that can adjust the output phase by changing the wide side dimension of a rectangular waveguide was once proposed. No dielectric or mental pins are involved in this phase shifter. It is expected that this phase shifter can have a high power handling capacity. In this paper, experimental research of this phase shifter at frequency 15.2 GHz is performed. Transmission efficiency and the ability of adjusting the output phase are measured in different conditions. Data are analyzed, it is found that this phase shifter can indeed realize adjusting phase in a range of 0°–360°. The transmission efficiency is strongly dependent on the gap between the adjustable metal plate and the waveguide. It can be over 95% when the gap is small enough. It is inferred that nice electric contact is favorable to the performance of this phase shifter. Furthermore, the power capacity of this waveguide phase shifter has been preliminary verified by Ku-band high-power microwave source. It is over 70 kW in the atmosphere. [ABSTRACT FROM PUBLISHER]

We investigate the bubble motion in transformer oil under a typical non-uniform electric field. Based on the principle of virtual work, an analytical equation is derived for the electric force putting on the bubbles. The bubble's visualized motion graphics are then obtained by using the finite-element method, which utilizes Comsol Multiphysics software. The effects of bubble radius and release position on the motion trajectory are studied. It is found that, under the non-uniform electric field, the bubbles have a long residence time between the electrodes. This accordingly can lead to a higher probability of forming a bubble-bridge along the bubble motion trajectory. The bubbles with a particular radius or release position are easier to form bubble-bridge between the electrodes. They can increase the chance of liquid breakdown. [ABSTRACT FROM AUTHOR]

• Anthocyanins are secondary metabolites of plants, and their accumulation is regulated by transcription factors. • Anthocyanins are accumulated at the initial stage of fruit ripening in purple pepper line 'Z1'. • CaMYB positively regulates the formation of purple color in the fruit of pepper. • CaMYB silencing enhances the sensitivity to cold stress in the fruit of pepper. Anthocyanin as secondary metabolites exits wildly in the plant kingdom, and its accumulation is regulated by transcription factors. However, little is known about role of CaMYB in fruit color of pepper. In this study, a purple-fruited pepper (Capsicum annuum L.) was selected and observed at 8 different stages (Z1−1–Z1−8) during fruit ripening (18, 23, 30, 35, 40, 45, 50, and 55 days after flowering). The results showed that higher accumulation of anthocyanin content was observed at 3 different stages (Z1−1– Z1−3) of fruit ripening and decreased in the following stage during fruit ripening, which primarily reflected in change of fruit color (from purple to yellow, and then to red). Expression of genes, especially CaMYB , in the biosynthetic pathway of anthocyanin was responsible for fruit color at 3 different stages (Z1−1– Z1−3) of fruit ripening. Further analysis showed that silencing of CaMYB resulted in poor accumulation of anthocyanin, suggesting the positive role of CaMYB in the metabolism of anthocyanin in pepper fruit. Our study will provide a basic insight for anthocyanin synthesis in fruit color formation. [ABSTRACT FROM AUTHOR]

• A pale green leaf mutant zylm was identified from the pepper mutant library. • Chlorophyll deficiency impaired growth of pepper, and anthocyanins accumulation inhibited increased photosynthesis. • Green leaf is dominant over pale green leaf and recessive over purple leaf. Limited genetic germplasm has been a problem for diversity of pepper for some years. Despite many mutants of plant have been reported in recent years, leaf anthocyanin or chlorophyll mutants were rarely identified in pepper, and the developmental and genetic characteristics of leaf-color remain poorly understood in pepper. Here, pale green leaf mutant, such as zylm mutant that was identified in an ethyl methane sulfonate mutagenized population of wild pepper (Capsicum annuum L.) 'Zunla', can be used to study the effect of leaf-color on pepper plants. Under natural field conditions, the leaves of zylm mutant plants exhibited impaired growth and pale green leaf throughout the entire growth season. Physiological and biological analysis of zylm mutant and other leaf-color mutants (yellow-green mutant bmy and purple leaf mutant Z1) revealed that chlorophyll deficiency was affected by down-regulation of chlorophyll synthesis gene expression, and resulted in impaired growth of pepper by inhibiting root activity, decreasing photosynthesis capacity, disturbing accumulation of soluble sugar and protein. Anthocyanins accumulation caused by up-regulation of anthocyanin synthesis gene expression increased root activity and contents of soluble sugar and protein, while its excessive accumulation limited the increase of photosynthesis capacity. Genetic analysis showed that formation of pale green leaf and purple leaf was controlled by nucleus. Green leaf is dominant over pale green leaf, and green leaf is recessive over purple leaf. Pale green leaf gene ZYLM and purple leaf PL were mapped in chromosome 3 and chromosome 9, indicating the diversity of leaf-color in pepper. [ABSTRACT FROM AUTHOR]

The Broad-complex Tramtrack and Bric-a-brac (BTB) domain participates in plant responses to biotic and abiotic stresses, however its role is unknown in pepper plants. CaBPM4 has meprin and TRAF homology (MATH) and BTB domains at its N- and C-termini, respectively, and it contains a 1589-bp full-length cDNA that encodes a protein containing 403 amino acids. In this study, the pepper gene CaBPM4 (Capsicum annuum BTB-POZ and MATH domain protein) was cloned, and its role in responses to Phytophthora capsici, cold, drought, and salt stress were characterized. The results of quantitative RT-PCR revealed that CaBPM4 was down-regulated under P. capsici infection, salicylic acid, H2O2, and abscisic acid treatments, while abiotic stresses, including salt, cold, and drought, enhanced its transcript level. Furthermore, CaBPM4 silencing significantly impaired resistance to P. capsici, apparently by altering the transcript level of defense-related genes CaPR1, CaDEF1, and CaSAR82 and reducing root activity. However, CaBPM4-silenced plants exhibited remarkably increased peroxidase activity and decreased malondialdehyde concentrations, indicating that CaBPM4 may enhance resistance to salt and drought stress. Further study should focus on the mechanism by which CaBPM4 regulates the defense response to P. capsici infection and abiotic stresses. [ABSTRACT FROM AUTHOR]

Chitin-binding proteins are pathogenesis-related gene family, which play a key role in the defense response of plants. However, thus far, little is known about the chitin-binding family genes in pepper (Capsicum annuum L.). In current study, 16 putative chitin genes (CaChi) were retrieved from the latest pepper genome database, and were classified into four distinct classes (I, III, IV and VI) based on their sequence structure and domain architectures. Furthermore, the structure of gene, genome location, gene duplication and phylogenetic relationship were examined to clarify a comprehensive background of the CaChi genes in pepper. The tissue-specific expression analysis of the CaChi showed the highest transcript levels in seed followed by stem, flower, leaf and root, whereas the lowest transcript levels were noted in red-fruit. Phytophthora capsici post inoculation, most of the CaChi (CaChiI3, CaChiIII1, CaChiIII2, CaChiIII4, CaChiIII6, CaChiIII7, CaChiIV1, CaChiVI1 and CaChiVI2) were induced by both strains (PC and HX-9). Under abiotic and exogenous hormonal treatments, the CaChiIII2, CaChiIII7, CaChiVI1 and CaChiVI2 were upregulated by abiotic stress, while CaChiI1, CaChiIII7, CaChiIV1 and CaChiIV2 responded to hormonal treatments. Furthermore, CaChiIV1-silenced plants display weakened defense by reducing (60%) root activity and increase susceptibility to NaCl stress. Gene ontology (GO) enrichment analysis revealed that CaChi genes primarily contribute in response to biotic, abiotic stresses and metabolic/catabolic process within the biological process category. These results exposed that CaChi genes are involved in defense response and signal transduction, suggesting their vital roles in growth regulation as well as response to stresses in pepper plant. In conclusion, these finding provide basic insights for functional validation of the CaChi genes in different biotic and abiotic stresses. [ABSTRACT FROM AUTHOR]

Extreme environmental conditions seriously affect crop growth and development, resulting in a decrease in crop yield and quality. However, small heat shock proteins (Hsp20s) play an important role in helping plants to avoid these negative impacts. In this study, we identified the expression pattern of the CaHsp25.9 gene in a thermo-tolerance pepper line R9 and thermo-sensitive line B6. The transcription of CaHsp25.9 was strongly induced by heat stress in both R9 and B6. The expression of CaHsp25.9 was induced by salt and drought stress in R9. Additionally, the CaHsp25.9 protein was localized in the cell membrane and cytoplasm. When silencing the CaHsp25.9 gene in the R9 line, the accumulation of malonaldehyde (MDA), relative electrolytic leakage, hydrogen peroxide, superoxide anion were increased, while total chlorophyll decreased under heat, salt, and drought stress. Over-expression of CaHsp25.9 in Arabidopsis resulted in decreased MDA, while proline, superoxide dismutase activity, germination, and root length increased under heat, salt, and drought stress. However, peroxidase activity was higher in drought stress but lower in heat and salt stress in transgenic Arabidopsis compared to the wild type (WT). Furthermore, the transcription of stress related genes was more highly induced in transgenic lines than WT. Our results indicated that CaHsp25.9 confers heat, salt, and drought stress tolerance to plants by reducing the accumulation of reactive oxygen species, enhancing the activity of antioxidant enzymes, and regulating the expression of stress-related genes. Therefore, these results may provide insight into plant adaption mechanisms developed in variable environments. • Silencing of CaHsp25.9 reduces pepper tolerance to heat, salt, and drought stress. • Over-expressing CaHsp25.9 enhances transgenic Arabidopsis tolerance to heat, salt and drought stress. • CaHsp25.9 enhances plants tolerance by reducing the accumulation of ROS. [ABSTRACT FROM AUTHOR]

Background: Carotenoids, the secondary metabolites terpenoids, are the largest factors that form the fruit color. Similar to flavonoids, they are not only safe and natural colorants of fruits but also play a role as stress response biomolecules., Methods: To study the contribution of the key genes in carotenoids biosynthesis, fruit-color formation, and in response to cold stress, we characterized the key regulatory factor CaATHB-12 from the HD-ZIP I sub-gene family members in pepper., Results: Cold stress enhanced carotenoid accumulation as compared with the normal condition. CaATHB-12 silencing through virus-induced gene silencing changed the fruit color by regulating the carotenoid contents. CaATHB-12 silencing increased the antioxidant enzyme activities in the fruits of pepper, exposed to cold stress, whereas CaATHB-12 overexpression decreased the activities of antioxidant enzymes in the transgenic Arabidopsis lines, exposed to cold stress, suggesting that CaATHB-12 is involved in the regulation of cold stress in the pepper fruits., Conclusion: Our research will provide insights into the formation of fruit color in pepper and contribution of CaATHB-12 in response to cold stress. Further study should be focused on the interaction between CaATHB-12 and its target gene., Competing Interests: The authors declare no conflict of interest. The authors have not received any funding or benefits from industry or elsewhere to conduct this study., (© 2020 Rui-Xing Zhang et al.)