More than 80% of land plant species can form symbioses with arbuscular mycorrhizal (AM) fungi, and nutrient transfer to plants is largely mediated through this partnership. Over the last few years, great progress has been made in deciphering the molecular mechanisms underlying the AM-mediated modulation of nutrient uptake progress, and a growing number of fungal and plant genes responsible for the uptake of nutrients from soil or transfer across the fungal–root interface have been identified. In this review, we outline the current concepts of nutrient exchanges within this symbiosis (mechanisms and regulation) and focus on P and N transfer from the fungal partner to the host plant, with a highlight on a possible interplay between P and N nutrient exchanges. Transporters belonging to the plant or AM fungi can synergistically process the transmembrane transport of soil nutrients to the symbiotic interface for further plant acquisition. Although much progress has been made to elucidate the complex mechanism for the integrated roles of nutrient transfers in AM symbiosis, questions still remain to be answered; for example, P and N transporters are less studied in different species of AM fungi; the involvement of AM fungi in plant N uptake is not as clearly defined as that of P; coordinated utilization of N and P is unknown; transporters of cultivated plants inoculated with AM fungi and transcriptomic and metabolomic networks at both the soil–fungi interface and fungi–plant interface have been insufficiently studied. These findings open new perspectives for fundamental research and application of AM fungi in agriculture.

Phosphate is one of the essential mineral nutrients. Phosphate transporter genes (PHTs) play an important role in Pi acquisition and homeostasis in tomato plants. However, basic biological information on PHT genes and their responses of symbiosis with arbuscular mycorrhizal in the genome remains largely unknown. We analyzed the physiological changes and PHT gene expression in tomatoes (Micro-Tom) inoculated with arbuscular mycorrhizal (AM) fungi (Funneliformis mosseae) under different phosphate conditions (P1: 0 µM, P2: 25 µM, and P3: 200 µM Pi). Twenty-three PHT genes were identified in the tomato genomics database. Protein sequence alignment further divided the 23 PHT genes into three groups, with similar classifications of exons and introns. Good colonization of plants was observed under low phosphate conditions (25 µM Pi), and Pi stress and AM fungi significantly affected P and N accumulation and root morphological plasticity. Moreover, gene expression data showed that genes in the SlPHT1 (SlPT3, SlPT4, and SlPT5) gene family were upregulated by Funneliformis mosseae under all conditions, which indicated that these gene levels were significantly increased with AM fungi inoculation. None of the analyzed SlPHT genes in the SlPH2, SlPHT3, SlPHT4, and SlPHO gene families were changed at any Pi concentration. Our results indicate that inoculation with AM fungi mainly altered the expression of the PHT1 gene family. These results will lay a foundation for better understanding the molecular mechanisms of inorganic phosphate transport under AM fungi inoculation.

Arbuscular mycorrhizal fungi (AMF) promote water and mineral nutrients uptake by plant roots, which can reduce the chemical fertilizer inputs in crop production. To gain better insight into the comparative effect of different strains of AMF in improving tomato performance at morphological and physiological levels, seedlings of two tomato cultivars (i.e., Better Boy and Roma) were inoculated with four strains of Glomus mosseae (i.e., HS 1–2, BEG 12, BEG 55, and BEG 54) under greenhouse conditions. Results showed that tomato growth and yield varied largely depending on the mycorrhizal strain and tomato cultivar, with wide variations in root colonization ranging from 5.30 to 78.63%. Overall, mycorrhization with BEG 54 showed significantly better tomato performance when compared to the BEG 55, HS 1–2 and BEG 12 strains. In the case of cultivars, Better Boy performed better than Roma cultivar in terms of growth, physiological traits, yield, and fruit quality. The highest plant height, dry matter, nitrogen, phosphorus, potassium, chlorophyll a, chlorophyll b, AMF colonization, yield, fruit juice, ascorbic acid, and titratable acidity contents were recorded in Better Boy cultivar while the highest stem diameter was found in Roma cultivar. Taken together, AMF colonization suggested a promising approach for large-scale tomato production by efficient absorption and utilization of nutrients, and encouraging plants’ symbiotic relationships with soil microorganisms.

The interaction between arbuscular mycorrhizal fungi (AM fungi) and Pseudomonas sp. has received considerable attention. The presence of biochar may affect these microorganisms, with subsequent modification of the phosphorus uptake and root morphology, and plant biomass accumulation. This research sought to identify, in the presence or absence of biochar, the effects of the interactions of mycorrhizal fungi and Pseudomonas sp. on the responses of phosphorus (P) and nitrogen (N) uptake and the root length, surface area, and volume of celery plants with low and high P fertilization under different substrate and soil conditions. The results indicate that strong growth responses of celery plants were observed due to the combination of AM fungi, Pseudomonas sp., and biochar with low P fertilization. A strong linear relationship was found between the plant root length and P accumulation in the shoot fraction in the present study. Increased P and N uptake occurred in treatments combining these microorganisms rather than alone, and this increase especially occurred in the presence of biochar. The low availability of P was substantially recovered by the association of these three aspects. The root morphology was greatly influenced by the biochar additives and in combination with AM fungi and Pseudomonas sp. The root colonization rate of AM fungi was increased by the combination of the inoculation of Pseudomonas sp. and biochar rather than AM fungi and/or Pseudomonas sp. These results indicate an accumulating effect of AM fungi, Pseudomonas sp., and biochar exists on the plant growth response and nutrient uptake because of the increasing root length, surface area, and volume, rather than root biomass.

Cucumber (Cucumis sativus L.) is a widely cultivated crop with rich germplasm resources, holding significant nutritional value. It also serves as an important model for studying epidermal cell fate and sex determination. Cucumbers are covered with multicellular and unbranched trichomes, including a specific type called spines found on the surface of the fruit. The presence and density of these fruit spines determine the visual quality of cucumber fruits. However, the key regulatory genes and mechanisms underlying cucumber fruit spine development remain poorly understood. In this study, we identified a WUSCHEL-related homeobox (WOX) family gene CsWOX3, which functioned as a typical transcriptional repressor and played a negative role in fruit spine development. Spatial–temporal expression analysis revealed that CsWOX3 exhibited a relatively high expression level in the cucumber female floral organs, particularly in the fruit exocarp. Knockout of CsWOX3 using CRISPR/Cas9 resulted in a significant 2-to-3-fold increase in the diameter of fruit spines base, while overexpression led to a 17% decrease in the diameter compared to the wild-type. A SQUAMOSA PROMOTER BINDING PROTEIN-LIKE transcription factor CsSPL15 could directly bind and activate the expression of CsWOX3, thereby suppressing the expression of downstream auxin-related genes, such as CsARF18. Additionally, the RING-finger type E3 ubiquitin ligase CsMIEL1-like interacted with the HD domain of CsWOX3, which might result in the ubiquitination and subsequent alteration in protein stability of CsWOX3. Collectively, our study uncovered a WOX transcription factor CsWOX3 and elucidated its expression pattern and biological function. This discovery enhances our comprehension of the molecular mechanism governing cucumber fruit spine morphogenesis.

Long-term soil mining with extensive cultivation practices and traditional breeding methods have declined the flavor and nutritional value of tomatoes. Apart from important mineral nutrients (i.e., nitrogen, phosphorus, and potassium), fungi known as arbuscular mycorrhizae (AM) can considerably improve the quality of agricultural production through higher phosphate uptake. Using hydroponically cultured commercially available tomato cultivars, we investigated the possible effects of mycorrhizae in improving the nutritional quality of tomato fruit. Funneliformis mosseae (syn. Glomus mosseae)-inoculated tomato plants were grown on a 1:1 mixture of peat and vermiculite, and different phosphorus levels were applied. RNAseq and metabolites were studied to confirm the relative gene expression and metabolites in fruit tissues. The results showed that AM inoculation with low phosphorus can significantly improve important fruit-quality traits such as free amino acids, lycopene (47.9%), and β-carotene (29.6%) without compromising the yield. Further, differentially expressed genes (DEGs) were identified by comparing the nutritional and ripening potential of fruits produced by mycorrhizal and non-mycorrhizal plants. Notably, carotenoids and sugars (BRIX values) were found to be higher in mycorrhized plants in contrast to non-mycorrhized plants. Therefore, the current study suggests mycorrhization as a promising approach for the production of high-quality tomato fruit for human consumption.