Plant-parasitic nematodes (PPNs), including root-knot nematodes (Meloidogyne spp.), cyst nematodes (Heterodera and Globodera spp.), and other economically significant nematode species, pose severe threats to global agriculture. These nematodes employ diverse survival strategies, such as dormancy in cysts or robust infective juvenile stages. Consequently, their management is challenging. Traditional control methods, such as the use of chemical nematicides, are increasingly scrutinized because of environmental and health concerns. This review focuses on the specific mechanisms employed by Bacillus spp., including nematicidal compound production, systemic resistance induction, and cuticle degradation, to target root-knot and cyst nematodes. These mechanisms offer sustainable solutions for managing nematodes and promoting soil health by enhancing microbial diversity and nutrient cycling. An integrated approach leveraging Bacillus-based biocontrol is proposed to maximize efficacy and agricultural sustainability.

Plant–insect interactions pose a major threat to global food security and ecological stability. This review provides a comprehensive synthesis of the molecular and physiological mechanisms underlying plant immunity against herbivorous insects, with emphasis on structural defenses, secondary metabolites, and hormone signaling pathways including Jasmonic acid, salicylic acid, and ethylene. It highlights key advances in understanding defense signaling crosstalk, effector-triggered responses, and the role of microbiota and environmental cues. The review further discusses insect counterstrategies and explores cutting-edge technologies-CRISPR/Cas9, RNA interference, and metabolic engineering that are reshaping pest management. However, challenges remain, including limited field validation of engineered traits, ecological trade-offs, and regulatory hurdles. We conclude by outlining future research directions focused on multi-omics integration, climate-resilient defense networks, and ethical deployment of plant biotechnologies within sustainable agroecosystems.

Relish, a transcription factor, is a critical downstream component of the immune deficiency (Imd) pathway and regulates host defense against bacterial infection by mediating antimicrobial peptide (AMP) synthesis. Understanding the immunological function of the mealworm beetle, Tenebrio molitor Relish (TmRelish) will be instructive in understanding insect immunity. In the present study, full-length ORF of TmRelish was retrieved from T. molitor-expressed sequence tags and RNA-seq database. The predicted TmRelish amino acid sequence contained an N-terminal Rel-homology domain; an Ig-like, plexin, and transcription factor domain; ankyrin repeat motifs; a nuclear localization signal; and a C-terminal death domain and shared the highly conserved structure of the Relish proteins of other insect species. TmRelish mRNA was detected in all developmental stages of the insect; however, the highest levels were detected in the larval gut tissue and adult hemocytes. TmRelish mRNA level was upregulated in the fat body, hemocyte, and gut tissue 9 h after infection of T. molitor larvae by the gram-negative bacteria, Escherichia coli. Furthermore, TmRelish knockdown led to significantly higher mortality of the E. coli-infected larvae, and significantly lower mortality of larvae infected with Staphylococcus aureus or Candida albicans. To elucidate the possible cause of mortality, we measured AMP transcription in the fat body, hemocytes, gut, and Malpighian tubules (MTs) of T. molitor larvae. TmRelish knockdown suppressed the expression of nine AMP genes in the larval fat body and gut tissue during E. coli infection, suggesting that TmRelish positively regulates AMP expression in both immune-related tissues, in response to E. coli challenge. Furthermore, negative regulation of some AMPs by TmRelish in the MTs, gut and hemocytes in response to C. albicans infection suggests a crosstalk between the Toll and Imd pathways.

The aim of this study was to investigate the antifungal activity of a cyclic tetrapeptide from Bacillus velezensis CE 100 against anthracnose-causing fungal pathogen Colletotrichum gloeosporioides. Antifungal compound produced by B. velezensis CE 100 was isolated and purified from ethyl acetate extract of B. velezensis CE 100 culture broth using octadecylsilane column chromatography. The purified compound was identified as cyclo-(prolyl-valyl-alanyl-isoleucyl) based on mass spectrometer and nuclear magnetic resonance analyses. This is the first report of the isolation of a cyclic tetrapeptide from B. velezensis CE 100 culture filtrate. Cyclic tetrapeptide displayed strong antifungal activity at concentration of 1000 µg/mL against C. gloeosporioides mycelial growth and spore germination. Our results demonstrate that the antifungal cyclic tetrapeptide from B. velezensis CE 100 has potential in bioprotection against anthracnose disease of plants caused by C. gloeosporioides.