Plant diseases caused by fungi are one of the major threats to global food security and understanding the interactions between fungi and plants is of great significance for plant disease control. The interaction between pathogenic fungi and plants is a complex process. From the perspective of pathogenic fungi, pathogenic fungi are involved in the regulation of pathogenicity by surface signal recognition proteins, MAPK signaling pathways, transcription factors, and pathogenic factors in the process of infecting plants. From the perspective of plant immunity, the signal pathway of immune response, the signal transduction pathway that induces plant immunity, and the function of plant cytoskeleton are the keys to studying plant resistance. In this review, we summarize the current research progress of fungi–plant interactions from multiple aspects and discuss the prospects and challenges of phytopathogenic fungi and their host interactions.

In fungi, the methylcitrate cycle converts cytotoxic propionyl-coenzyme A (CoA) to pyruvate, which enters gluconeogenesis. The glyoxylate cycle converts acetyl-CoA to succinate, which enters gluconeogenesis. The tricarboxylic acid cycle is a central carbon metabolic pathway that connects the methylcitrate cycle, the glyoxylate cycle, and other metabolisms for lipids, carbohydrates, and amino acids. Fungal citrate synthase and 2-methylcitrate synthase as well as isocitrate lyase and 2-methylisocitrate lyase, each evolved from a common ancestral protein. Impairment of the methylcitrate cycle leads to the accumulation of toxic intermediates such as propionyl-CoA, 2-methylcitrate, and 2-methylisocitrate in fungal cells, which in turn inhibits the activity of many enzymes such as dehydrogenases and remodels cellular carbon metabolic processes. The methylcitrate cycle and the glyoxylate cycle synergistically regulate carbon source utilization as well as fungal growth, development, and pathogenic process in pathogenic fungi.

Rice blast is one of the most serious diseases affecting rice yield which is caused by Magnaporthe oryzae, a model organism for studies on plant pathogenic fungi. Lipids stored in M. oryzae cells have been shown to be crucial for the development of appressorium turgor and the ability of the pathogen to cause infection. Nile red staining is a common method to study lipid dynamics in phytopathogenic fungi. However, the disadvantages of this dye include its wide spectrum, poor water solubility, and susceptibility to quenching. Boron dipyrromethene (BODIPY) is a new type of fluorescent dye that has a different emission wavelength to that of Nile red as well as many desirable spectral and chemical properties. In this study, we used BODIPY to stain the lipids in M. oryzae cells to seek a possible substitute to Nile red in the study of lipid dynamics in plant pathogenic fungi. Our data showed that through simple and routine procedures, BODIPY was able to distinctly label lipids in the cells of mycelia and conidia. The positions of lipids labeled by BODIPY were essentially identical to those labeled by Nile red, but with more clear fluorescence labelling, lower background, and higher specificity. The use of BODIPY to stain germinating M. oryzae conidia allowed the lipid dynamics to be clearly tracked during this process. We also achieved double and multiple fluorescent staining conidia by combining BODIPY with the red fluorescent protein mCherry and other fluorescent dyes, such as Calcofluor white and DAPI, in conidia, mycelia, and sexual structures of M. oryzae. These results indicate that BODIPY is an ideal fluorescent dye for staining fungal lipids and provide a method for the study of the lipid dynamics and lipid metabolism in plant pathogenic fungi.

RNA interference (RNAi) has emerged as a potent mechanism for combating pathogenic fungi and oomycetes over the past decades. It offers a promising gene-silencing approach by targeting crucial genes involved in diseases caused by economically and scientifically significant fungal pathogens, such as Botrytis cinerea and Fusarium species. Simultaneously, nano-agro-products have gained attention as alternatives to traditional fungicides in plant protection strategies. However, the instability of naked RNA molecules outside the cellular environment presents a challenge, as they degrade rapidly, limiting their efficacy for prolonged disease control. Concerns regarding the toxicity of protective nanoparticles to non-target organisms have also arisen. Integrating RNAi with nano-agro-products, particularly nanocarriers, to form RNA-nano complexes has demonstrated significant potential, providing enhanced RNA stability, reduced toxicity, and extended disease control. This review explores the mechanisms of RNA-nano complexes-mediated plant protection, addressing RNA stability and nano-toxicity issues while examining the prospects of RNA-nano complex research in plant pathogen management.