Black pepper is an industrial crop with high economic and export value. However, black pepper production in Vietnam has been seriously affected by the root-knot nematodes, Meloidogyne spp. The purpose of this study was to select active endophytic bacteria (EB) for the cost-effective and environmentally friendly management of Meloidogyne sp. Thirty-four EB strains were isolated. Of these, five isolates displayed the highest activity, demonstrating 100% mortality of J2 nematodes. These active EB were identified based on sequencing and phylogenetic analysis of the 16S rRNA gene; notably, all the potential endophytic bacterial strains belong to the genus of Bacillus. In greenhouse tests, Bacillus megaterium DS9 significantly reduced nematodes in the soil and pepper plant roots with great inhibition values of 81.86% and 73.11%, respectively, with the lowest rate of nematodes built up at 0.23. This active antinematodes strain also showed good effect on promoting pepper plant growth. Some enzymatic activities, including chitinase and protease activity related to the biocontrol of Meiloidogyne sp., were also detected. The results investigated in the current study suggested that these selected EB strains may be good candidates for biocontrol agents of Meloidogyne sp., and plant promoting effects. The results also enhanced the novel active antinematode endophytic bacterial communities.

In this study, 90 root samples were collected from 30 black pepper farms in three provinces in the Central Highlands of Vietnam. A total of 352 endophytic bacteria were isolated and their morphology described. An in vitro assay on the antifungal activity of these isolates was then conducted and 47 isolates were found to have antagonistic activity on Phytophthora fungi. The antifungal activity of the 47 isolates was evaluated in vivo by shoot assay. Among these 47 isolates, 6 were selected for further investigation. The six isolates were classified and identified by sequencing the 16S RNA gene and phylogeny. The results showed that all six endophytic bacteria belong to the following species of Bacillus genus: B. siamensis, B. amyloliquefaciens, B. velezenis, and B. methylotrophiycus. Enzymatic activity related to the antifungal activity of the six potent isolates was determined; it showed that they possessed high chitinase and protease activities. These isolates were applied for black pepper seedlings in greenhouse. The results showed three promising isolates: B. siamensis EB.CP6, B. velezensis EB.KN12, and B. methylotrophycus EB.KN13. Black pepper seedlings treated with the promising bacteria had the lowest rate of root disease (8.45–11.21%) and lower fatal rate (11.11–15.55%) compared to the control group (24.81% and 24.44%). In addition, the three promising isolates strongly affected the growth of the black pepper seedlings in greenhouse. The plant height, length of roots, and fresh biomass of the seedlings in the treated plots were higher than those in the control plots. Thus, the endophytic bacterial isolates have the potential to act as biocontrol agent for the sustainable production of black pepper.

Thrombospondin-1 (TSP-1) is an extracellular matrix protein produced by astrocytes, which can promote synaptogenesis. The regulation of astrocytic TSP-1 involves extracellular ATP through the activation of P2Y receptors coupled to various protein kinase signaling pathways. However, not much is known about the mechanisms regulating TSP-1 expression in primary cortical astrocytes after a traumatic brain injury. Using an in-vitro model of central nervous system trauma that stimulates the release of ATP, we found that trauma-induced expression and release of TSP-1 involved purinergic signaling as both expression and release were significantly attenuated by pyridoxalphosphate-6-azophenyl-2′-4′-disulfonic acid, a P2 receptor antagonist. Further antagonist studies with reactive blue 2 point to a role for P2Y4, as reactive blue 2 is a potent antagonist for rat P2Y4 receptors. In addition, the injury-induced expression of TSP-1 was significantly attenuated by the inhibition of extracellular signal-regulated kinase and p38/mitogen-activated protein kinase, whereas injury-induced release of TSP-1 was significantly blocked by the inhibition of extracellular signal-regulated kinase and Akt. Using an in-vivo model of a moderate parasagittal fluid-percussion brain injury, we found that TSP-1 levels were increased when compared with those in sham animals in the cortex, thalamus, and hippocampus. We conclude that TSP-1 expression after injury can be regulated by the activation of P2 receptors coupled with protein kinase signaling pathways and suggest that purinergic signaling, by regulating TSP expression, may play an important role in cell–matrix and cell–cell interactions such as those occurring during central nervous system repair.

Robusta coffee is a major commercial crop in the Central Highland of Vietnam with high economic and export value. However, this crop is adversely affected by various pathogens, particularly nematodes. This study aimed to screen active anti-nematode rhizobacterial strains for sustainable coffee production. Among more than 200 isolates, the isolate TUN03 demonstrated efficient biocontrol with nearly 100% mortality of J2 coffee nematodes Meloidogyne spp. and 84% inhibition of nematode egg hatching. This active strain was identified as Pseudomonas aeruginosa TUN03 based on its 16S rRNA gene sequence and phylogenetic analysis. In greenhouse tests, the strain TUN03 significantly reduced the coffee nematode population in the rhizome-soil with an 83.23% inhibition rate and showed plant growth-promoting effects. Notably, this is the first report of the nematicidal effect of P. aeruginosa against coffee nematodes. This potent strain further showed an antifungal effect against various crop-pathogenic fungi and was found to be the most effective against Fusarium solani F04 (isolated from coffee roots) with a 70.51% inhibition rate. In addition, high-performance liquid chromatography analysis revealed that this bacterial strain also secretes plant growth regulators including indole acetic acid (IAA), gibberellic acid (GA3), kinetin, and zeatin in significant amounts of 100, 2700, 37, and 9.5 µg/mL, respectively. The data from this study suggest that P. aeruginosa TUN03 may be a potential biocontrol agent and biofertilizer for the sustainable production of Robusta coffee and other crops.

Vietnam is the most prominent black pepper producer and exporter in the world. In 2020, the cultivated area of black pepper in Vietnam was 132.000 hectares and its production was 270.000 tons, in which the Central Highlands region took about 70% of both the cultivated area and production [1]. Hence, this region is thought to be the capital of black pepper cultivation and production in Vietnam. Numerous researches have investigated biodiversity and collected various beneficial endophytic bacteria from this plant in this region; however, traditional methods only were used to isolate such bacteria [2], [3], [4], [5]. Therefore, these studies have a limitation to providing insight into the profiles of the endophytic microorganism dataset in the black pepper plant. Most recently, our work based on the 16S rRNA gene amplicon sequencing revealed an insight into profiles of microbial diversity and its functionality from the sample collected from a forest in this region; however, that work was just focused on soil microbiome dataset from the dry deciduous dipterocarp forest in Yok Don national park [6]. To our knowledge, a dataset of endophytic microbiome of black pepper plant cultivated in the Central Highlands remains unclear.