Inter-cellular and inter-kingdom signaling systems of various levels of complexity regulate pathogenic and mutualistic interactions between bacteria, parasites, and fungi and animal and plant hosts. Inter-kingdom interactions between mutualistic bacteria such as rhizobia and legumes during nodulation and between fungi and plants during mycorrhizal associations, are characterized by the extensive exchange of molecular signals, which allow nitrogen and phosphate assimilation, respectively. A novel aspect of this signaling exchange is the existence of specific structures, the exosomes, that carry important molecules that shape the plant–pathogen interactions. Exosomes contain a wide array of molecules, such as lipids, proteins, messenger RNA, and microRNAs, that play important roles in cell-to-cell communication in animal and plant cells by affecting gene expression and other physiological activity in distant cells within the same organism (e.g., during cancer metastases and neuron injuries). In plant cells, it has been recently reported that exosomes go beyond organism boundaries and inhibit a pathogenic interaction in plants. Plant produce and send exosomes loaded with specific small miRNA which inhibit the pathogen infection, but the pathogen can also produce exosomes carrying pro-pathogenic proteins and microRNAs. Therefore, exosomes are the important bridge regulating the signal exchange. Exosomes are small membrane-bound vesicles derived from multivesicular bodies (MVBs), which carries selected cargos from the cytoplasm (protein, lipids, and microRNAs) and under certain circumstances, they fuse with the plasma membrane, releasing the small vesicles as cargo-carrying exosomes into the extracellular space during intercellular and inter-kingdom communication. Animal and plant proteomic studies have demonstrated that tetraspanin proteins are an integral part of exosome membranes, positioning tetraspanins as essential components for endosome organization, with key roles in membrane fusion, cell trafficking, and membrane recognition. We discuss the similarities and differences between animal tetraspanins and plant tetraspanins formed during plant–microbe interactions and their potential role in mutualistic communication.

Zeolite, a microporous mineral with strong ion binding, can enhance nutrient availability and growth of plants, such as maize (Zea mays L.). Arbuscular mycorrhizal (AM) symbiosis has also been shown to enhance nutrient availability and growth of plants, including maize. However, the interaction between AM symbiosis and zeolite is poorly understood. In this study, the effect on growth of maize was examined following soil treatment with N-enriched (ZN+) zeolite, which could retain 19.68% N, or N-free zeolite (ZN−), compared to N-enriched or N-free vermiculite (VN+ and VN−). There was a 2.7-times increase in the growth of maize under ZN+ treatment compared to ZN−, indicating that N could be released from zeolite for plant growth, and a 3.8-times increase with ZN+ treatment compared to VN− or VN+, indicating that zeolite was more effective than vermiculite in releasing N for plant growth. Subsequently, ZN+ and ZN− treatments were examined with non-AM (M−) and AM (M+) treatments using Rhizophagus irregularis. ZN+ M+ treatment led to higher AM colonization and development compared to M+ ZN−treatment, indicating an interaction of AM in roots with N from zeolite. PCA revealed improvements in leaf N content, photosynthetic pigments, photosynthetic performance, and secondary metabolites with M+ ZN+ treatment, which was also observed in comparison to M−ZN+ and M− ZN−treatments, further supporting the benefit of combining N from zeolite with an AM fungus. The combination of N released from N-enriched zeolite and AM symbiosis offers a promising alternative to chemical fertilizers to improve maize growth.