Genome-wide transcriptome and gene family analysis reveal candidate genes associated with potassium uptake of maize colonized by arbuscular mycorrhizal fungi.

BACKGROUND: Potassium (K) is an essential nutrient for plant growth and development. Maize (Zea mays) is a widely planted crops in the world and requires a huge amount of K fertilizer. Arbuscular mycorrhizal fungi (AMF) are closely related to the K uptake of maize. Genetic improvement of maize K utilization efficiency will require elucidating the molecular mechanisms of maize K uptake through the mycorrhizal pathway. Here, we employed transcriptome and gene family analysis to elucidate the mechanism influencing the K uptake and utilization efficiency of mycorrhizal maize. METHODS AND RESULTS: The transcriptomes of maize were studied with and without AMF inoculation and under different K conditions. AM symbiosis increased the K concentration and dry weight of maize plants. RNA sequencing revealed that genes associated with the activity of the apoplast and nutrient reservoir were significantly enriched in mycorrhizal roots under low-K conditions but not under high-K conditions. Weighted gene correlation network analysis revealed that three modules were strongly correlated with K content. Twenty-one hub genes enriched in pathways associated with glycerophospholipid metabolism, glycerolipid metabolism, starch and sucrose metabolism, and anthocyanin biosynthesis were further identified. In general, these hub genes were upregulated in AMF-colonized roots under low-K conditions. Additionally, the members of 14 gene families associated with K obtain were identified (ARF: 38, ILK: 4, RBOH: 12, RUPO: 20, MAPKK: 89, CBL: 14, CIPK: 44, CPK: 40, PIN: 10, MYB: 174, NPF: 79, KT: 19, HAK/HKT/KUP: 38, and CPA: 8) from maize. The transcript levels of these genes showed that 92 genes (ARF:6, CBL:5, CIPK:13, CPK:2, HAK/HKT/KUP:7, PIN:2, MYB:26, NPF:16, RBOH:1, MAPKK:12 and RUPO:2) were upregulated with AM symbiosis under low-K conditions. CONCLUSIONS: This study indicated that AMF increase the resistance of maize to low-K stress by regulating K uptake at the gene transcription level. Our findings provide a genome-level resource for the functional assignment of genes regulated by K treatment and AM symbiosis in K uptake-related gene families in maize. This may contribute to elucidate the molecular mechanisms of maize response to low K stress with AMF inoculation, and provided a theoretical basis for AMF application in the crop field.

Intricate microbe-plant-metabolic remodeling mediated by intercropping enhances the quality of Panax quinquefolius L.

Improving the cultivation mode and technology for traditional Chinese medicine has become important for its sustainable development. Monoculture enhances plant diseases, which decreases yield and quality. Intercropping is an effective measure to counterbalance that negative effect. In this study, we focused on Panax quinquefolium L. (ginseng) and four treatments were set up: the control without intercropping, P. quinquefolius + ryegrass (Lolium perenne L.), P. quinquefolius + red clover (Trifolium pratense L.), and P. quinquefolius + ryegrass + red clover. An LC-MS/MS system was used to detect the changes in the P. quinquefolius secondary metabolites, and high-throughput sequencing technology was used to determine the changes in the P. quinquefolius' rhizosphere soil microorganisms. Ginsenoside content, soil enzyme activities, and arbuscular mycorrhizal infection rate of P. quinquefolius were also measured using HPLC, ELISA kits, and microscopy, respectively. Co-intertia and Pearson's analysis were performed to explore the relationship between the metabolites and the P. quinquefolius microorganisms. Intercropping significantly increased the content of ginsenoside metabolites and recruited a large number of beneficial bacteria to the P. quinquefolius rhizosphere. The P. quinquefolius secondary metabolites were associated with the rhizosphere microbial community. For example, the dominant microorganisms, such as Acidobacteriota and Chloroflexi, played a key role in promoting the synthesis of ginsenoside Rd and (20R) ginsenoside Rg3 by P. quinquefolius. Intercropping led to changes in the P. quinquefolius secondary metabolites by driving and reshaping the rhizosphere microorganisms. These findings revealed the potential application of intercropping for improving the quality of P. quinquefolius.

Mycorrhizal symbiosis and the nitrogen nutrition of forest trees.

Terrestrial plants form primarily mutualistic symbiosis with mycorrhizal fungi based on a compatible exchange of solutes between plant and fungal partners. A key attribute of this symbiosis is the acquisition of soil nutrients by the fungus for the benefit of the plant in exchange for a carbon supply to the fungus. The interaction can range from mutualistic to parasitic depending on environmental and physiological contexts. This review considers current knowledge of the functionality of ectomycorrhizal (EM) symbiosis in the mobilisation and acquisition of soil nitrogen (N) in northern hemisphere forest ecosystems, highlighting the functional diversity of the fungi and the variation of symbiotic benefits, including the dynamics of N transfer to the plant. It provides an overview of recent advances in understanding 'mycorrhizal decomposition' for N release from organic or mineral-organic forms. Additionally, it emphasises the taxon-specific traits of EM fungi in soil N uptake. While the effects of EM communities on tree N are likely consistent across different communities regardless of species composition, the sink activities of various fungal taxa for tree carbon and N resources drive the dynamic continuum of mutualistic interactions. We posit that ectomycorrhizas contribute in a species-specific but complementary manner to benefit tree N nutrition. Therefore, alterations in diversity may impact fungal-plant resource exchange and, ultimately, the role of ectomycorrhizas in tree N nutrition. Understanding the dynamics of EM functions along the mutualism-parasitism continuum in forest ecosystems is essential for the effective management of ecosystem restoration and resilience amidst climate change. KEY POINTS: • Mycorrhizal symbiosis spans a continuum from invested to appropriated benefits. • Ectomycorrhizal fungal communities exhibit a high functional diversity. • Tree nitrogen nutrition benefits from the diversity of ectomycorrhizal fungi.

The Defective in Autoregulation (DAR) gene of Medicago truncatula encodes a protein involved in regulating nodulation and arbuscular mycorrhiza.

BACKGROUND: Legumes utilize a long-distance signaling feedback pathway, termed Autoregulation of Nodulation (AON), to regulate the establishment and maintenance of their symbiosis with rhizobia. Several proteins key to this pathway have been discovered, but the AON pathway is not completely understood. RESULTS: We report a new hypernodulating mutant, defective in autoregulation, with disruption of a gene, DAR (Medtr2g450550/MtrunA17_Chr2g0304631), previously unknown to play a role in AON. The dar-1 mutant produces ten-fold more nodules than wild type, similar to AON mutants with disrupted SUNN gene function. As in sunn mutants, suppression of nodulation by CLE peptides MtCLE12 and MtCLE13 is abolished in dar. Furthermore, dar-1 also shows increased root length colonization by an arbuscular mycorrhizal fungus, suggesting a role for DAR in autoregulation of mycorrhizal symbiosis (AOM). However, unlike SUNN which functions in the shoot to control nodulation, DAR functions in the root. CONCLUSIONS: DAR encodes a membrane protein that is a member of a small protein family in M. truncatula. Our results suggest that DAR could be involved in the subcellular transport of signals involved in symbiosis regulation, but it is not upregulated during symbiosis. DAR gene family members are also present in Arabidopsis, lycophytes, mosses, and microalgae, suggesting the AON and AOM may use pathway components common to other plants, even those that do not undergo either symbiosis.

Genome-Wide Identification and Expression Analysis of SlNRAMP Genes in Tomato under Nutrient Deficiency and Cadmium Stress during Arbuscular Mycorrhizal Symbiosis.

Arbuscular mycorrhizal (AM) fungi are well known for enhancing phosphorus uptake in plants; however, their regulating roles in cation transporting gene family, such as natural resistance-associated macrophage protein (NRAMP), are still limited. Here, we performed bioinformatics analysis and quantitative expression assays of tomato SlNRAMP 1 to 5 genes under nutrient deficiency and cadmium (Cd) stress in response to AM symbiosis. These five SlNRAMP members are mainly located in the plasma or vacuolar membrane and can be divided into two subfamilies. Cis-element analysis revealed several motifs involved in phytohormonal and abiotic regulation in their promoters. SlNRAMP2 was downregulated by iron deficiency, while SlNRAMP1, SlNRAMP3, SlNRAMP4, and SlNRAMP5 responded positively to copper-, zinc-, and manganese-deficient conditions. AM colonization reduced Cd accumulation and expression of SlNRAMP3 but enhanced SlNRAMP1, SlNRAMP2, and SlNRMAP4 in plants under Cd stress. These findings provide valuable genetic information for improving tomato resilience to nutrient deficiency and heavy metal stress by developing AM symbiosis.

X-ray fluorescence and XANES spectroscopy revealed diverse potassium chemistries and colocalization with phosphorus in the ectomycorrhizal fungus Paxillus ammoniavirescens.

Ectomycorrhizal (ECM) fungi play a major role in forest ecosystems and managed tree plantations. Particularly, they facilitate mineral weathering and nutrient transfer towards colonized roots. Among nutrients provided by these fungi, potassium (K) has been understudied compared to phosphorus (P) or nitrogen (N). The ECM fungus Paxillus ammoniavirescens is a generalist species that interacts with the root of many trees and can directly transfer K to them, including loblolly pine. However, the forms of K that ECM fungi can store is still unknown. Here, we used synchrotron potassium X-ray fluorescence (XRF) and K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy on P. ammoniavirescens growing in axenic conditions to investigate the K chemistries accumulating in the center and the edge of the mycelium. We observed that various K forms accumulated in different part of the mycelium, including K-nitrate (KNO3), K-C-O compounds (such as K-tartrate K2(C4H4O6) and K-oxalate (K2C2O4)), K-S and K-P compounds. Saprotrophic fungi have been shown to excrete carboxylic acids, which in turn play a role in soil mineral weathering. Our finding of several K counter-ions to carboxylic acids may suggest that, besides their direct transfer to colonized roots, K ions can also be involved in the production of compounds necessary for sourcing nutrients from their surrounding environment by ECM fungi. Additionally, this work reveals that XANES spectroscopy can be used to identify the various forms of K accumulating in biological systems.

Alternative splicing regulation in plants by SP7-like effectors from symbiotic arbuscular mycorrhizal fungi.

Most plants in natural ecosystems associate with arbuscular mycorrhizal (AM) fungi to survive soil nutrient limitations. To engage in symbiosis, AM fungi secrete effector molecules that, similar to pathogenic effectors, reprogram plant cells. Here we show that the Glomeromycotina-specific SP7 effector family impacts on the alternative splicing program of their hosts. SP7-like effectors localize at nuclear condensates and interact with the plant mRNA processing machinery, most prominently with the splicing factor SR45 and the core splicing proteins U1-70K and U2AF35. Ectopic expression of these effectors in the crop plant potato and in Arabidopsis induced developmental changes that paralleled to the alternative splicing modulation of a specific subset of genes. We propose that SP7-like proteins act as negative regulators of SR45 to modulate the fate of specific mRNAs in arbuscule-containing cells. Unraveling the communication mechanisms between symbiotic fungi and their host plants will help to identify targets to improve plant nutrition.

Mycorrhizal associations of temperate forest seedlings mediate rhizodeposition, but not soil carbon storage, under elevated nitrogen availability.

Tree-mycorrhizal associations are associated with patterns in nitrogen (N) availability and soil organic matter storage; however, we still lack a mechanistic understanding of what tree and fungal traits drive these patterns and how they will respond to global changes in soil N availability. To address this knowledge gap, we investigated how arbuscular mycorrhizal (AM)- and ectomycorrhizal (EcM)-associated seedlings alter rhizodeposition in response to increased seedling inorganic N acquisition. We grew four species each of EcM and AM seedlings from forests of the eastern United States in a continuously 13C-labeled atmosphere within an environmentally controlled chamber and subjected to three levels of 15N-labeled fertilizer. We traced seedling 15N uptake from, and 13C-labeled inputs (net rhizodeposition) into, root-excluded or -included soil over a 5-month growing season. N uptake by seedlings was positively related to rhizodeposition for EcM- but not AM-associated seedlings in root-included soils. Despite this contrast in rhizodeposition, there was no difference in soil C storage between mycorrhizal types over the course of the experiment. Instead root-inclusive soils lost C, while root-exclusive soils gained C. Our findings suggest that mycorrhizal associations mediate tree belowground C investment in response to inorganic N availability, but these differences do not affect C storage. Continued soil warming and N deposition under global change will increase soil inorganic N availability and our seedling results indicate this could lead to greater belowground C investment by EcM-associated trees. This potential for less efficient N uptake by EcM-trees could contribute to AM-tree success and a shift toward more AM-dominated temperate forests.

Improving semi-arid agroecosystem services with cover crop mixes.

Winter wheat (Triticum aestivum, L.) production in the semi-arid US Northern High Plains (NHP) is challenged by frequent droughts and water-limited, low fertility soils. Composted cattle manure (compost) and cover crops (CC) are known to provide agroecosystem services such as improved soil health, and in the CC case, increased plant diversity, and competition with weedy species. The main concern of planting CC in winter wheat fallow rotation in regions that are more productive than the NHP, however, is the soil moisture depletion. It is unknown however, whether addition of CC to compost-amended soils in the NHP will improve soil properties and agroecosystem health without compromising already low soil water content. The main objective of this study was to assess the effects of four CC treatments amended with compost (45 Mg ha-1) or inorganic fertilizer (IF) (.09 Mg ha-1 mono-ammonium phosphate, 11-52-0 and 1.2 Mg ha-1ammonium sulfate, 21-0-0) on the presence of weeds, soil and plant total carbon (C), nitrogen (N), and biological dinitrogen (N2) fixation (BNF). Mycorrhizal Mix (MM), Nitrogen Fixer Mix (NF), Soil Building Mix (SB), a monoculture of phacelia (Phacelia tanacetifolia Benth L.) (PH), and a no CC control (no CC) were grown in native soil kept at 7% soil moisture in a greenhouse for a period of nine weeks. When amended with compost, MM was the most beneficial (48 g m-2 BNF and 1.7% soil C increase). SB had the highest germination, aboveground biomass, and decreased weed biomass by 60%. It also demonstrated the second highest amount of BNF (40 g m-2) and soil C increase by 1.5%. On contrary, IF hindered BNF by almost 70% in all legume-containing CC treatments and reduced soil C by 15%.

Transformation and degradation of tebuconazole and its metabolites in constructed wetlands with arbuscular mycorrhizal fungi colonization.

Arbuscular mycorrhizal fungi (AMF) colonization has been used in constructed wetlands (CWs) to enhance treatment performance. However, its role in azole (fungicide) degradation and microbial community changes is not well understood. This study aims to explore the impact of AMF on the degradation of tebuconazole and its metabolites in CWs. Total organic carbon levels were consistently higher with the colonization of AMF (AMF+; 9.63- 16.37 mg/L) compared to without the colonization of AMF (AMF-; 8.79-14.48 mg/L) in CWs. Notably, tebuconazole removal was swift, occurring within one day in both treatments (p = 0.885), with removal efficiencies ranging from 94.10 % to 97.83 %. That's primarily due to rapid substrate absorption at the beginning, while degradation follows with a longer time. Four metabolites were reported in CWs first time: tebuconazole hydroxy, tebuconazole lactone, tebuconazole carboxy acid, and tebuconazole dechloro. AMF decreased the abundance of tebuconazole dechloro in the liquid phase, suggesting an inhibitory effect of AMF on dechlorination processes. Furthermore, tebuconazole carboxy acid and hydroxy were predominantly found in plant roots, with a higher abundance observed in AMF+ treatments. Metagenomic analysis highlighted an increasing abundance in bacterial community structure in favor of beneficial microorganisms (xanthomonadales, xanthomonadaceae, and lysobacter), along with a notable presence of functional genes like codA, NAD, and deaD in AMF+ treatments. These findings highlight the positive influence of AMF on tebuconazole stress resilience, microbial community modification, and the enhancement of bioremediation capabilities in CWs.

Extramatrical mycelial biomass is mediated by fine root mass and ectomycorrhizal fungal community composition across tree species.

In many ecosystems, a large fraction of gross primary production is invested in mycorrhiza. Ectomycorrhizal (ECM) mycelium is involved in regulating soil carbon and nutrient cycling. However, little is known about how mycelial biomass, production and turnover differ depending on ECM fungal community composition and associated tree species. We quantified fine root biomass and length using soil cores, and mycelial traits (biomass, production, and turnover) using mesh-bags and ergosterol analysis, and identified ECM exploration types by Illumina MiSeq sequencing of four ECM-dominated tree species (Picea asperata, Larix gmelinii, Quercus aquifolioides and Betula albosinensis) in subalpine forest. The ECM fungal community composition separated between needle-leaved and broadleaved species, and between evergreen and deciduous species. The ratio of mycelial to fine root biomass was similar across the species regardless of genus-scale community composition and the relative abundance of exploration types. Compared to the other species, Q. aquifolioides displayed higher fine root biomass and mycelial biomass and production, dominated by contact-short exploration type. Mycelial turnover rate tended to be lowest in P. asperata, dominated by medium-long exploration type. Much higher production of mycelium and only slightly higher turnover rate in Q. aquifolioides suggests that its steady-state mycelial biomass would be higher than of the other species. Moreover, compared to the two deciduous species, with similar production but somewhat lower turnover rate, the standing crop of mycelium in P. asperata may stabilize at a higher value. Our findings, that exploration type may affect production and turnover, highlight the importance of characterizing ECM fungal communities by exploration types when estimating the contribution of mycelium biomass to forest carbon sink and storage.

Combined use of arbuscular mycorrhizal fungi and alkaline lignin enhance phosphorus nutrition and alleviate cadmium stress in lettuce (Lactuca sativa L.).

The excessive application of phosphorus (P) fertiliser and its poor utilisation efficiency have led to significant amounts of P being retained in agricultural soils in unavailable forms. The application of alkaline lignin to soil and its inoculation with arbuscular mycorrhizal fungi (AMF) have both been shown to improve plant P nutrition. However, their combined effects on soil P transformation remain unclear, particularly in cadmium (Cd)-contaminated soils. A potting experiment was conducted to examine the combined effects of AMF and alkaline lignin on soil P and Cd bioavailability and on the uptake of P and Cd by lettuce (Lactuca sativa L.) that were grown for 56 d in a growth chamber. Combined AMF and alkaline lignin treatment increased soil P availability and alkaline phosphatase activity. It furthermore increased bioavailable Cd concentrations of rhizosphere and bulk soils by 48 % and 72 %, respectively, and the Cd concentration in roots by 85 %, but the Cd concentration was not affected in the edible parts (shoots) of the lettuce. Moreover, the combined treatment increased shoot biomass by 26-70 % and root biomass by 99-164 %. Our findings suggested that the combined use of AMF and alkaline lignin mobilised both P and Cd in soil but did not increase the accumulation of Cd in the shoots of plants growing in Cd-contaminated soils, these results would provide guideline for increasing Cd tolerance of plants and their yield.

The rootstock modifies the arbuscular mycorrhizal community of the root system, while the influence of the scion is limited in grapevines.

Understanding the effects of grapevine rootstock and scion genotypes on arbuscular mycorrhizal fungi (AMF), as well as the roles of these fungi in plant development, could provide new avenues for adapting viticulture to climate change and reducing agrochemical inputs. The root colonization of 10 rootstock/scion combinations was studied using microscopy and metabarcoding approaches and linked to plant development phenotypes. The AMF communities were analysed using 18S rRNA gene sequencing. The 28S rRNA gene was also sequenced for some combinations to evaluate whether the method changed the results. Root colonization indexes measured by microscopy were not significantly different between genotypes. Metabarcoding analyses showed an effect of the rootstock genotype on the ß-diversity and the enrichment of several taxa with both target genes, as well as an effect on the Chao1 index with the 18S rRNA gene. We confirm that rootstocks recruit different AMF communities when subjected to the same pedoclimatic conditions, while the scion has little or no effect. Significant correlations were observed between AMF community composition and grapevine development, suggesting that AMF have a positive effect on plant growth. Given these results, it will be important to define consensus methods for studying the role of these beneficial micro-organisms in vineyards.

Vineyard management systems influence arbuscular mycorrhizal fungi recruitment by grapevine rootstocks in New Zealand.

AIMS: Arbuscular mycorrhizal fungi (AMF) can perform significant functions within sustainable agricultural ecosystems, including vineyards. Increased AMF diversity can be beneficial in promoting plant growth and increasing resilience to environmental changes. To effectively utilize AMF communities and their benefits in vineyard ecosystems, a better understanding of how management systems influence AMF community composition is needed. Moreover, it is unknown whether AMF communities in organically managed vineyards are distinct from those in conventionally managed vineyards. METHODS AND RESULTS: In this study, vineyards were surveyed across the Marlborough region, New Zealand to identify the AMF communities colonizing the roots of different rootstocks grafted with Sauvignon Blanc and Pinot Noir in both conventional and organic systems. The AMF communities were identified based on spores isolated from trap cultures established with the collected grapevine roots, and by next-generation sequencing technologies (Illumina MiSeq). The identified AMF species/genera belonged to Glomeraceae, Entrophosporaceae, and Diversisporaceae. The results revealed a significant difference in AMF community composition between rootstocks and in their interaction with management systems. CONCLUSIONS: These outcomes indicated that vineyard management systems influence AMF recruitment by rootstocks and some rootstocks may therefore be more suited to organic systems due to the AMF communities they support. This could provide an increased benefit to organic systems by supporting higher biodiversity.

Breaking barriers: improving time and space resolution of arbuscular mycorrhizal symbiosis with single-cell sequencing approaches.

The cell and molecular bases of arbuscular mycorrhizal (AM) symbiosis, a crucial plant-fungal interaction for nutrient acquisition, have been extensively investigated by coupling traditional RNA sequencing techniques of roots sampled in bulk, with methods to capture subsets of cells such as laser microdissection. These approaches have revealed central regulators of this complex relationship, yet the requisite level of detail to effectively untangle the intricacies of temporal and spatial development remains elusive.The recent adoption of single-cell RNA sequencing (scRNA-seq) techniques in plant research is revolutionizing our ability to dissect the intricate transcriptional profiles of plant-microbe interactions, offering unparalleled insights into the diversity and dynamics of individual cells during symbiosis. The isolation of plant cells is particularly challenging due to the presence of cell walls, leading plant researchers to widely adopt nuclei isolation methods. Despite the increased resolution that single-cell analyses offer, it also comes at the cost of spatial perspective, hence, it is necessary the integration of these approaches with spatial transcriptomics to obtain a comprehensive overview.To date, few single-cell studies on plant-microbe interactions have been published, most of which provide high-resolution cell atlases that will become crucial for fully deciphering symbiotic interactions and addressing future questions. In AM symbiosis research, key processes such as the mutual recognition of partners during arbuscule development within cortical cells, or arbuscule senescence and degeneration, remain poorly understood, and these advancements are expected to shed light on these processes and contribute to a deeper understanding of this plant-fungal interaction.

The costs and benefits of symbiotic interactions: variable effects of rhizobia and arbuscular mycorrhizae on Vigna radiata accessions.

BACKGROUND: The symbiosis among plants, rhizobia, and arbuscular mycorrhizal fungi (AMF) is one of the most well-known symbiotic relationships in nature. However, it is still unclear how bilateral/tripartite symbiosis works under resource-limited conditions and the diverse genetic backgrounds of the host. RESULTS: Using a full factorial design, we manipulated mungbean accessions/subspecies, rhizobia, and AMF to test their effects on each other. Rhizobia functions as a typical facilitator by increasing plant nitrogen content, plant weight, chlorophyll content, and AMF colonization. In contrast, AMF resulted in a tradeoff in plants (reducing biomass for phosphorus acquisition) and behaved as a competitor in reducing rhizobia fitness (nodule weight). Plant genotype did not have a significant effect on AMF fitness, but different mungbean accessions had distinct rhizobia affinities. In contrast to previous studies, the positive relationship between plant and rhizobia fitness was attenuated in the presence of AMF, with wild mungbean being more responsive to the beneficial effect of rhizobia and attenuation by AMF. CONCLUSIONS: We showed that this complex tripartite relationship does not unconditionally benefit all parties. Moreover, rhizobia species and host genetic background affect the symbiotic relationship significantly. This study provides a new opportunity to re-evaluate the relationships between legume plants and their symbiotic partners.

Tree richness increased biomass carbon sequestration and ecosystem stability of temperate forests in China: Interacted factors and implications.

Biodiversity loss and forest degradation have received increasing attention worldwide, and their effects on forest biomass carbon storage and stability have not yet been well defined. This study examined 1275 tree plots using the field survey method to quantify the effects of tree diversity, tree sizes, and mycorrhizal symbiont abundance on biomass carbon storages (Cs) and NDVI (Normalized Difference Vegetation Index)-based ecosystem stability (standard deviation/mean NDVI = NDVI_S) during the field survey period from 2008 to 2018. Our data showed Cs and NDVI_S averaged at 31-108 t ha-1 and 32.04-49.28, respectively, and positive relations between Cs and NDVI_S were observed (p < 0.05). Large forest-type and regional variations were found in these two parameters. Broadleaf forests had 74% of Cs (p < 0.05) of the conifer forests, but no differences were in NDVI_S. Cold regions at high latitudes had 71% of NDVI_S in the warm regions at low latitudes, while no differences were in Cs. Moist regions at high longitudes had 2.04 and 1.28-fold higher Cs and NDVI_S (p < 0.05). The >700 m a.s.l. regions had 1.24-fold higher Cs (p < 0.01) than the <700 m a.s.l. regions, but similar NDVI_S (p > 0.05). Nature Reserves had 1.94-fold higher Cs but 30% lower NDVI_S than outside Reserves (p < 0.001). > 40-year-old forests had 1.3- and 2-fold higher Cs and NDVI_S than the young forests. Structural equation modeling and hierarchical partitioning revealed the driving paths responsible for these variations. Tree richness was positively associated with Cs and ecosystem stability, contributing 21.6%-30.6% to the total effects on them; tree sizes significantly promoted the Cs, but had negligible impacts on NDVI_S. MAT's total effects on NDVI_S of conifer forests were 40% higher than that of broadleaf forests, MAP's total effects on Cs varied with forest types; arbuscular mycorrhizal tree dominance exhibited a smaller positive impact on Cs and ecosystem stability in comparison to other factors. Our findings underscore that the significance of climatic-adapted forest management, diversity conservation, and big-sized tree protections can support the achievement of carbon neutrality in China from biomass carbon sequestration and ecosystem stability.

Lipids Mediate Arbuscule Development and Senescence in Tomato Roots Colonized by Arbuscular Mycorrhizae Fungus under Drought Stress.

Arbuscular mycorrhizae (AM) symbiosis can enhance plant resistance to drought stress (DS). This study aimed to investigate the DS effects on lipids at different stages of symbiosis and to link lipid profiles to arbuscule dynamics in tomato roots colonized by AM fungi. DS increased mycorrhizal colonization and arbuscule abundance at an early stage but decreased them at a later stage, delayed arbuscule development, and accelerated arbuscule senescence at a later stage. DS decreased the contents of phospholipids (PLs) and saturated neutral lipids (NLs) at the early stage but increased the contents of saturated PLs and unsaturated NLs at the late stage. Specifically, DS inhibited AM-specific PL contents but increased AM-specific NL contents, which was supported by the expression of RAM2, STR/STR2. These data indicate the negative effect of DS on AM symbiosis and arbuscule dynamics with the effect size depending on the symbiosis stage, which highlights the importance of the symbiosis stage under abiotic stress.

The use of biostimulants as a key to sustainable hydroponic lettuce farming under saline water stress.

BACKROUND: The utilization of high-quality water in agriculture is increasingly constrained by climate change, affecting availability, quality, and distribution due to altered precipitation patterns, increased evaporation, extreme weather events, and rising salinity levels. Salinity significantly challenges salt-sensitive vegetables like lettuce, particularly in a greenhouse. Hydroponics water quality ensures nutrient solution stability, enhances nutrient uptake, prevents contamination, regulates pH and electrical conductivity, and maintains system components. This study aimed to mitigate salt-induced damage in lettuce grown via the floating culture method under 50 mM NaCl salinity by applying biostimulants. RESULTS: We examined lettuce's physiological, biochemical, and agronomical responses to salt stress after applying biostimulants such as amino acids, arbuscular mycorrhizal fungi, plant growth-promoting rhizobacteria (PGPR), fulvic acid, and chitosan. The experiment was conducted in a greenhouse with a randomized complete block design, and each treatment was replicated four times. Biostimulant applications alleviated salt's detrimental effects on plant weight, height, leaf number, and leaf area. Yield increases under 50 mM NaCl were 75%, 51%, 31%, 34%, and 33% using vermicompost, PGPR, fulvic acid, amino acid, and chitosan, respectively. Biostimulants improved stomatal conductance (58-189%), chlorophyll content (4-10%), nutrient uptake (15-109%), and water status (9-107%). They also reduced MDA content by 26-42%. PGPR (1.0 ml L‒1), vermicompost (2 ml L‒1), and fulvic acid (40 mg L‒1) were particularly effective, enhancing growth, yield, phenol, and mineral content while reducing nitrate levels under saline conditions. CONCLUSIONS: Biostimulants activated antioxidative defense systems, offering a sustainable, cost-effective solution for mitigating salt stress in hydroponic lettuce cultivation.