Salt and osmotic stress seriously restrict the growth, development, and productivity of horticultural crops in the greenhouse. The papain-like cysteine proteases (PLCPs) participate in multi-stress responses in plants. We previously demonstrated that salt and osmotic stress affect cysteine protease 15 of pepper (Capsicum annuum L.) (CaCP15); however, the role of CaCP15 in salt and osmotic stress responses is unknown. Here, the function of CaCP15 in regulating pepper salt and osmotic stress resistance was explored. Pepper plants were subjected to abiotic (sodium chloride, mannitol, salicylic acid, ethrel, methyl jasmonate, etc.) and biotic stress (Phytophthora capsici inoculation). The CaCP15 was silenced through the virus-induced gene silencing (VIGS) and transiently overexpressed in pepper plants. The full-length CaCP15 fragment is 1568 bp, with an open reading frame of 1032 bp, encoding a 343 amino acid protein. CaCP15 is a senescence-associated gene 12 (SAG12) subfamily member containing two highly conserved domains, Inhibitor 129 and Peptidase_C1. CaCP15 expression was the highest in the stems of pepper plants. The expression was induced by salicylic acid, ethrel, methyl jasmonate, and was infected by Phytophthora capsici inoculation. Furthermore, CaCP15 was upregulated under salt and osmotic stress, and CaCP15 silencing in pepper enhanced salt and mannitol stress resistance. Conversely, transient overexpression of CaCP15 increased the sensitivity to salt and osmotic stress by reducing the antioxidant enzyme activities and negatively regulating the stress-related genes. This study indicates that CaCP15 negatively regulates salt and osmotic stress resistance in pepper via the ROS-scavenging.

Anthracnose is a widespread plant disease affecting vegetables, flowers, crops, and fruit trees, causing significant economic losses. It occurs at various stages of pepper growth, leading to rotting and shedding in later stages. The aim of this study was to explore the relationship with anthracnose occurrence by analyzing the physicochemical properties and microbiota changes in the inter-root soil of pepper under different susceptibility levels to reveal the key microecological factors and dominant microbial populations and to provide reference for ecological control. Illumina Miseq sequencing was first used to evaluate the physicochemical properties and microbial taxa in pepper inter-root soil across different health statuses and identify key parameters associated with anthracnose. Subsequently, PICRUSt2 (systematic genetic Investigation of communities by Reconstruction of observed States 2) and FUNGuild (Fungi Functional Guild) V1.0 online platform were used to predict the activities of inter-root bacteria and fungi. The findings indicated that healthy peppers had significantly higher inter-root soil nutrient levels and enzyme activity compared to sensitive peppers. There were significant differences between their community structures. In alpha-diversity analysis, inter-root soil microbial richness and diversity were significantly higher in healthy peppers than in susceptible peppers. At the bacterial taxonomic level, the comparative prevalence of Acidobacteria in highly resistant plants, resistant plants, and susceptible plants decreased sequentially. At the genus level, the relative abundance of Vicinamibacteraceae and RB41 was markedly elevated in disease-resistant inter-root soils than in disease-susceptible soils. At the fungal level, the comparative prevalence of Ascomycetes in highly resistant plants, resistant plants, and susceptible plants increased sequentially. Differences in function are mainly manifested in apoptosis and mycelial development.

This experimental study used peanut shell biochar and fermented cow manure as the main raw materials forming a substrate for tomato plants. Substrates were created from peanut shell biochar, fermented cow manure, slag, and vermiculite mixed in volume ratios of 6:0:1:2, 5:1:1:2, 4:2:1:2, and 3:3:1:2, respectively. Comparisons were made to a control substrate composed of peat, slag, and vermiculite in a volume ratio of 6:1:2, respectively. As the proportion of biochar in the substrate increased, the bulk density showed a downward trend while the total porosity, aeration porosity, and water holding capacity showed upward trends. As the proportion of cow manure increased, the total N, available K, Ca, and Mg in the substrate increased. Tomatoes demonstrated similar or better growth than the control at experimental substrate composition ratios of 6:0:1:2 and 5:1:1:2. This was reflected in seedling strength index, seedling growth, chlorophyll content, root growth, plant carbohydrates, purine metabolism, caffeine metabolism, galactose metabolism, and starch and sucrose metabolism. The results of this study indicate the experimental substrate composition ratios of 6:0:1:2 and 5:1:1:2 were the most beneficial in terms of supporting the growth of tomato plants. The study confirms biochar in composite substrate promotes plant growth by improving the root environment and plant metabolism. This investigation provides new information to moderate the use of peat and support efforts to achieve carbon neutrality through the creative utilization of agricultural waste.