The Comprehensive Effects of Rhizophagus intraradices and P on Root System Architecture and P Transportation in Citrus limon L.

Abstract

Both arbuscular mycorrhizal fungi (AMF) and phosphorus (P) collectively influence the root system architecture (RSA), but whether the combination of the two affects RSA, particularly lateral root formation, is unknown. In the present study, a pot experiment was conducted to evaluate the effects of an arbuscular mycorrhizal fungus (Rhizophagus intraradices) on the RSA of lemon (Citrus limon L.) seedlings under 0 (P0) and 50 mg/kg (P50) P levels. Moreover, P and carbohydrate content; acid phosphatase activity; and the expression of P transporter genes (PTs), phosphatase genes (PAPs), and lateral-root-related genes; were determined. Our results show that root mycorrhizal colonization and mycorrhizal dependency of lemon plants are significantly higher under P0 than under P50 conditions. AMF significantly promoted the plant growth performance of lemon, irrespective of substrate P levels. The RSA parameters of AMF plants, including total root length, projected area, surface area, average diameter, volume, and second- and third-order lateral root numbers, were distinctly increased under the two P levels compared to those of non-AMF plants. Mycorrhizal treatment also induced higher carbohydrate (sucrose, glucose, and fructose) and P contents, along with a higher activity of root acid phosphatase. The expression of P-related genes, including ClPAP1, ClPT1, ClPT3, ClPT5, and ClPT7, as well as the expression of lateral-root-related genes (ClKRP6, ClPSK6, and ClRSI-1), was dramatically upregulated by AMF inoculation, irrespective of substrate P levels. Principal component analysis showed that root P and carbohydrate contents, as well as the expression of ClKRP6 and ClPSK6, were positively correlated with RSA traits and lateral root development. Our study demonstrates that mycorrhizas accelerate the P acquisition and carbohydrate accumulation of lemon plants by upregulating the expression of lateral-root-related genes, thereby positively improving the RSA. Furthermore, AMF had a greater impact on the RSA of lemon than substrate P levels.

Indigenous and commercial isolates of arbuscular mycorrhizal fungi display differential effects in Pyrus betulaefolia roots and elicit divergent transcriptomic and metabolomic responses

“…Further, AMF can improve plant growth, root morphology, regulate host gene expression and cellular metabolism through various signaling molecules ( Lopez-Raez et al., 2010 ; Rivero et al., 2015 ; Hill et al., 2018 ). Previous studies have shown that AMF can regulate the expression of genes associated with root development to promote plant root development, promote the expression of root transporter genes, and improve acquisition of mineral elements by plants ( Liu et al., 2022 ; Wu et al., 2022 ). In a complimentary way, plant roots can regulate the colonization of AMF by changing the synthesis of its metabolites including that of fatty acids, flavonoids and signaling molecules ( Larose et al., 2002 ; Jin et al., 2016 ; Kameoka et al., 2019 ).…”

Exogenous Easily Extractable Glomalin-Related Soil Protein Stimulates Plant Growth by Regulating Tonoplast Intrinsic Protein Expression in Lemon

“…The seeds of the plant material, lemon ( Citrus limon L.), were provided by the Resear-ch Institute of Fruit and Tea, Hubei Academy of Agricultural Sciences. The method of Liu et al [ 44 ] was referred to regarding seed disinfection and germination, with the germination carried out in sterilized sand (121 °C, 0.1 MPa, 1 h) for 4 weeks under the conditions of 28/20 °C (day/night) and 80% relative humidity. One non-mycorrhizal seedling with two euphylla of uniform size were selected and transplanted into one pot.…”

Mycorrhizal Symbiosis Enhances P Uptake and Indole-3-Acetic Acid Accumulation to Improve Root Morphology in Different Citrus Genotypes

“…These segments were cleared using 10% potassium hydroxide and stained with a 0.05% trypan blue solution [19]. The rate of mycorrhizal colonization in the lateral roots was determined following the method described by Shao et al [14], using a Leica DME binocular light microscope (Leica Microsystem Inc., Wetzlar, Germany) for examination, and calculated as the percentage of AM infected root lengths against total root length.…”

“…However, the influence of AMF on root system architecture (RSA) is subject to various factors, including soil P levels and hormonal balances. Studies on trifoliate orange (Poncirus trifoliata) and tea plants (Camellia sinensis L. O. Kuntze) have revealed that AMF infection promotes RSA, with improvements in root length, volume, surface area, and lateral root formation, which are further amplified by higher P concentrations [13,14]. In addition, AMF inoculation can also affect root hair growth, including their density and length under different soil P levels, and mycorrhiza-induced changes in root hair growth were closely related to upregulated expressions of expansin and simultaneous auxin accumulation in roots [15,16].…”