Root-associated endophytic fungi modulate endogenous auxin and cytokinin levels to improve plant biomass and root morphology of trifoliate orange

Root-associated endophytic fungi like Serendipita indica and arbuscular mycorrhizal(AM) fungi can improve plant growth and root construction, but the potential mechanism is unclear. In this study, Funneliformis mosseae(an AM fungus) and S. indica, singly or in combination were inoculated into trifoliate orange(Poncirus trifoliata) seedlings, to assess changes in biomass and root morphological traits, coupled with auxins and cytokinins concentrations in leaves and roots and the expression of auxin synthesis and transporter protein genes. After 20 weeks of inoculation with these fungi, shoot and root biomass, root total length, taproot length, average diameter, surface area, volume, and the number of lateral roots in 1st-, 2nd-, and 3rd-order were improved, and S. indica showed a relatively greater effect than F. mosseae and dual inoculation. Endophytic fungal inoculation also significantly increased the concentration of indoleacetic acid, indole butyric acid, trans-zeatin,dihydrozeatin, and isopentenyl adenine in leaves and roots, whilst F. mosseae and S. indica exhibited relatively greater effects on leaves and roots, respectively. Correlation analysis revealed that both biomass and root morphological traits(except root projected area) were significantly positively associated with endogenous auxins and cytokinins. In addition, the inoculated plants recorded comparatively higher expression levels of indoleacetic acid synthesis genes(PtTAA1, PtTAR2, PtYUC3, PtYUC4, PtYUC6, and PtYUC8) and indoleacetic acid transporter protein genes(PtAUX1, PtLAX1, PtLAX2, PtLAX3, PtPIN1, PtPIN3, PtPIN4, PtABCB1, and PtABCB19) than the non-inoculated plants, among which F. mosseae and S. indica showed better effects in leaves and roots, respectively. These results suggest that root-associated endophytic fungi improved plant growth and root architecture, which were associated with changes in endogenous auxins and cytokinins.

Mycorrhiza improves plant growth and photosynthetic characteristics of tea plants in response to drought stress

Tea plants are sensitive to soil moisture deficit,with the level of soil water being a critical factor affecting their growth and quality.Arbuscular mycorrhizal fungi(AMF)can improve water and nutrient absorption,but it is not clear whether AMF can improve the photosynthetic characteristics of tea plants.A potted study was conducted to determine the effects of Claroideoglomus etunicatum on plant growth,leaf water status,pigment content,gas exchange,and chlorophyll fluorescence parameters in Camellia sinensis cv.Fuding Dabaicha under well-watered(WW)and drought stress(DS)conditions.Root mycorrhizal colonization and soil hyphal length were significantly reduced by the eightweek DS treatment.AMF inoculation displayed a significant increase in shoot and root biomass production.The relative water content,leaf water potential,nitrogen balance index,pigment content,maximum photometric effect(Fv/Fm,QY_max),and steady-state photometric effect Y(II)(QY_Lss)decreased dramatically,while the leaf water saturation deficit and steady-state non-photochemical fluorescence quenching(NPQ_Lss)generally increased under DS conditions.Mycorrhizal treatment induced significantly higher relative water content,leaf water potential,nitrogen balance index,pigment(chlorophyll,flavonoid,and anthocyanin)content,net photosynthesis rate,transpiration rate,stomatal conductance,intercellular CO_(2)concentration,QY_max,and QY_Lss;however,it resulted in a lower leaf water saturation deficit and NPQ_Lss under both WW and DS conditions,as compared with nonmycorrhizal plants.These results imply that AMF promoted tea plant growth and alleviated negative effects of DS by promoting gas exchange,regulating the water status of leaves,and regulating photosynthetic parameters.

Identification of PtGai(a DELLA protein)in trifoliate orange and expression patterns in response to drought stress

Gibberellins(GAs)are an important hormone in regulating plant growth and development,and DELLA protein is an essential negative regulator of GA signal transduction.The aim of the study was to clone a GAinhibiting protein DELLA from trifoliate orange(Poncirus trifoliata L.Raf.)and to analyze the bioinformations and expression patterns of the protein gene in tissues and in response to drought stress.A DELLA protein was isolated from trifoliate orange and named as PtGai(Genebank number:MZ170959).The PtGai protein had 1731 bp open reading frames,along with 576 amino acid codes,and also grouped with sweet orange(XM_006430552.4).The PtGai protein sequence was 65%homology with the sequences of DELLA proteins in other plant families.PtGai protein existed in the nucleus based on the prediction of subcellular localization.PtGai protein could be expressed in roots,stems,and leaves,along with the highest expression in stems.PtGai was upregulated by drought stress in leaves and roots,along with the decrease of root total GA concentration and the inhibition of shoot and root biomass production.It indicated the characteristics of PtGai protein and the roles of PtGai in GA synthesis and plant growth.

Interaction between Earthworms and Arbuscular Mycorrhizal Fungi in Plants:A Review

Different kinds of soil animals and microorganisms inhabit the plant rhizosphere,which function closely to plant roots.Of them,arbuscular mycorrhizal fungi(AMF)and earthworms play a critical role in sustaining the soilplant health.Earthworms and AMF belong to the soil community and are soil beneficial organisms at different trophic levels.Both of them improve soil fertility and structural development,collectively promoting plant growth and nutrient acquisition capacity.Earthworm activities redistribute mycorrhizal fungi spores and give diversified effects on root mycorrhizal fungal colonization.Dual inoculation with both earthworms and AMF strongly magnifies the response on plant growth through increased soil enzyme activities and changes in soil nutrient availability,collectively mitigating the negative effects of heavy metal pollution in plants and soils.This thus enhances phytoremediation and plant disease resistance.This review simply outlines the effects of earthworms and AMF on the soil-plant relationship.The effects of earthworms on root AMF colonization and activities are also analyzed.This paper also summarizes the interaction between earthworms and AMF on plants along with suggested future research.

Arbuscular mycorrhizal fungi and endophytic fungi differentially modulate polyamines or proline of peach in response to soil flooding

Symbiotic fungi are involved in plant flooding tolerance,while the underlying mechanism is not yet known.Since polyamines(PAs)and proline are also associated with stress tolerance,it is hypothesized that the enhancement of stress resistance by symbiotic fungi is associated with changes in PAs and/or proline.The aim of this study was to analyze the effect of inoculation with Funneliformis mosseae and Serendipita indica on plant growth,PAs,and proline and the metabolisms in peach(Prunus persica)under flooding.Two-week flooding did not affect root colonization frequence of F.mosseae,while it promoted root colonization frequence of S.indica.Under flooding,plants inoculated with F.mosseae and S.indica maintained relatively higher growth rates than uninoculated plants.Funneliformis mosseae promoted root ornithine(Orn)contentration and arginine(Arg)and Orn decarboxylase activities under flooding,which promoted putrescine(Put),cadaverine(Cad),and spermidine(Spd)contentrations.Conversely,S.indica decreased contentrations of Arg,Orn,and agmatine and Arg decarboxylase activities,thus decreasing PA contentrations under flooding.Polyamines were negatively correlated with the expression of PA uptake transporter genes,PpPUT1 and PpPUT2,in peach.Polyamine transporter genes of F.mosseae(FmTPO)and S.indica(SiTPO)were regulated by flooding,of which FmTPO1 was positively correlated with Put,Cad,and Spd,along with positive correlations of Spd with SiTPO1,SiTPO2,and SiTPO4.Under flooding,F.mosseae decreased proline concentration,while S.indica increased proline concentration and correlated with expression of a△^(1)-pyrroline-5-carboxylate synthetase gene,PpP5CS2.It was thus concluded that F.mosseae modulated polyamine accumulation,while S.indica induced proline accumulation to tolerate flooding.