Salicylic Acid Spray Delays Sand Pear Fruit Senescence during Room Temperature Shelf Life by Regulating Antioxidant Capacity and Senescence-Related Genes.

'Whangkeumbae' (Pyrus pyrifolia) is a variety of sand pear fruit well-known for its smooth surface and good taste. However, the fruit quality is adversely affected by postharvest ethylene production. Therefore, improving postharvest shelf life by regulating fruit senescence is critical to promoting the 'Whangkeumbae' fruit industry. Here, we investigated the effect of salicylic acid (SA) spray on fruit senescence in sand pears during room temperature shelf life. Exogenous SA reduced polyphenol oxidase (PPO) activity and malondialdehyde (MDA) content during room temperature shelf life. Additionally, SA effectively maintained the fruit skin coloration and increased the activity of antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). SA treatment inhibited PpPPO1 expression and upregulated PpSOD1, PpAPX6, and PpGST2 expression. Furthermore, SA application downregulated the expression of PpACO2, PpEIN3a, PpNCED1, and PpAOC2, while upregulating PpNPR-1, PpTAR2, and PpCOMT1 during room temperature shelf life. SA treatment also influenced cell wall metabolism and modification genes by inhibiting PpPG1, PpPME2, and PpCEL3 and inducing PpPGIP1 expression. Additionally, SA treatment affected sugar and acid metabolism genes and increased the expression of PpSPS1, PpSUS1, PpSOT1, PpTMT4, PpSWEET15, and PpcyNAD-MDH, but suppressed the expression of PpcyNADP-ME. The Pearson correlation analysis indicated that PPO activity and MDA content were positively correlated with the expression of PpPPO1, PpACO2, PpEIN3a, PpNCED1, PpAOC2, PpPG1, PpPME2, PpCEL3, and PpcyNDA-MDH. Conversely, these factors were negatively associated with the activities of SOD, POD, CAT, and APX, as well as the expression levels of PpSOD1, PpPOD1, PpCAT1, PpAPX6, PpGST2, PpNPR-1, PpTAR2, PpCOMT1, PpPGIP1, PpSPS1, PpSUS1, PpSOT1, PpTMT4, PpSWEET15, and PpcyNAD-MDH. Our results reveal that exogenous SA could delay fruit senescence in sand pear fruit by regulating various biochemical and molecular mechanisms and can be used to effectively extend fruit shelf life during room temperature storage. However, further research is necessary to determine whether the fruits sprayed with SA are suitable for direct human consumption.

A synthetic light-inducible photorespiratory bypass enhances photosynthesis to improve rice growth and grain yield.

Bioengineering of photorespiratory bypasses is an effective strategy for improving plant productivity by modulating photosynthesis. In previous work, two photorespiratory bypasses, the GOC and GCGT bypasses, increased photosynthetic rates but decreased seed-setting rate in rice (Oryza sativa), probably owing to excess photosynthate accumulation in the stem. To solve this bottleneck, we successfully developed a new synthetic photorespiratory bypass (called the GMA bypass) in rice chloroplasts by introducing Oryza sativa glycolate oxidase 1 (OsGLO1), Cucurbita maxima malate synthase (CmMS), and Oryza sativa ascorbate peroxidase7 (OsAPX7) into the rice genome using a high-efficiency transgene stacking system. Unlike the GOC and GCGT bypass genes driven by constitutive promoters, OsGLO1 in GMA plants was driven by a light-inducible Rubisco small subunit promoter (pRbcS); its expression dynamically changed in response to light, producing a more moderate increase in photosynthate. Photosynthetic rates were significantly increased in GMA plants, and grain yields were significantly improved under greenhouse and field conditions. Transgenic GMA rice showed no reduction in seed-setting rate under either test condition, unlike previous photorespiratory-bypass rice, probably reflecting proper modulation of the photorespiratory bypass. Together, these results imply that appropriate engineering of the GMA bypass can enhance rice growth and grain yield without affecting seed-setting rate.

Fusarium equiseti-inoculation altered rhizosphere soil microbial community, potentially driving perennial ryegrass growth and salt tolerance.

Fusarium equiseti is an effective plant growth-promoting fungi that induce systemic disease resistance in plants. However, the role of F. equiseti in regulating salt stress response and the underlying mechanisms remain largely unknown. Here, we investigated the effect of F. equiseti Z7 strain on the growth and salt stress response in perennial ryegrass. Additionally, the role of Z7 in regulating the abundance, composition, and structure of native microbial communities in the rhizosphere soil was determined. We observed that Z7 could produce indole-3-acetic acid (IAA) and siderophores. Hence, Z7 inoculation further enhanced plant growth and salt tolerance in perennial ryegrass. Inoculating Z7 increased K+ and decreased Na+ in plant tissues. Z7 inoculation also enhanced soil quality by reducing soluble salt and increasing available phosphorus. Moreover, inoculating Z7 altered the compositions of bacterial and fungal communities in the rhizosphere soil. For instance, beneficial bacterial genera, such as Flavobacterium, Enterobacter, Agrobacterium, and Burkholderiales were dominantly enriched in Z7-inoculated soil. Interestingly, the relative abundance of these genera showed significantly positive correlations with the fresh weight of perennial ryegrass. Our results demonstrate that Z7 could remarkably promote plant growth and salt tolerance by regulating ion homeostasis in plant tissues and microbial communities in the rhizosphere soil. This study provides a scientific foundation for applying microbes to improve plant growth under extreme salt stress conditions.

Genome-wide identification and molecular characterization of the AP2/ERF superfamily members in sand pear (Pyrus pyrifolia).

BACKGROUND: 'Whangkeumbae' (Pyrus pyrifolia) is a typical climacteric fruit variety of sand pear with excellent taste. However, the rapid postharvest ethylene production limits the shelf life of 'Whangkeumbae' fruit. AP2/ERF superfamily is a large family of transcription factors involved in plant growth and development, including fruit ripening and senescence through the ethylene signaling pathway. The numbers and functions of AP2/ERF superfamily members in sand pear remain largely unknown. RESULTS: In this study, a total of 234 AP2/ERF family members were identified through the transcriptome of Pyrus pyrifolia 'Whangkeumbae' (17 genes) and Pyrus pyrifolia genome (223 genes) analyses. Six genes (Accession: EVM0023062.1, EVM0034833.1, EVM0027049.1, EVM0034047.1, EVM0028755.1, EVM0015862.1) identified via genome analysis shared 100% identity with PpERF14-L, PpERF5-L, PpERF3a, PpERF3, PpERF017 and PpERF098, respectively, which were identified from transcriptome sequencing. Further, the AP2/ERF superfamily members were divided into AP2, ERF, and RAV subfamilies, each comprising 38, 188, and 8 members, respectively. Tissue-specific expression analysis showed that PpERF061, PpERF113, PpERF51L-B, PpERF5-L, and PpERF017 were predominantly expressed in fruits than in other tissues. Additionally, PpERF5-L and PpERF017 showed higher expressions at the early stage of fruit development. While, PpERF51B-L exhibited higher expression during the fruit ripening stage. Besides, PpERF061 and PpERF113 had pronounced expressions during fruit senescence. CONCLUSION: These results indicate that PpERF061, PpERF113, PpERF51L-B, PpERF5-L, and PpERF017 could play crucial roles in sand pear fruit development, ripening, and senescence. Overall, this study provides valuable information for further functional analysis of the AP2/ERF genes during fruit ripening and senescence in sand pear.

Transcriptomic Analysis Provides Novel Insights into the Heat Stress-Induced Response in Codonopsis tangshen.

Codonopsis tangshen Oliv (C. tangshen) is a valuable traditional Chinese medicinal herb with tremendous health benefits. However, the growth and development of C. tangshen are seriously affected by high temperatures. Therefore, understanding the molecular responses of C. tangshen to high-temperature stress is imperative to improve its thermotolerance. Here, RNA-Seq analysis was performed to investigate the genome-wide transcriptional changes in C. tangshen in response to short-term heat stress. Heat stress significantly damages membrane stability and chlorophyll biosynthesis in C. tangshen, as evidenced by pronounced malonaldehyde (MDA), electrolyte leakage (EL), and reduced chlorophyll content. Transcriptome analysis showed that 2691 differentially expressed genes (DEGs) were identified, including 1809 upregulated and 882 downregulated. Functional annotations revealed that the DEGs were mainly related to heat shock proteins (HSPs), ROS-scavenging enzymes, calcium-dependent protein kinases (CDPK), HSP-HSP network, hormone signaling transduction pathway, and transcription factors such as bHLHs, bZIPs, MYBs, WRKYs, and NACs. These heat-responsive candidate genes and TFs could significantly regulate heat stress tolerance in C. tangshen. Overall, this study could provide new insights for understanding the underlying molecular mechanisms of thermotolerance in C. tangshen.

Genotypic-specific hormonal reprogramming and crosstalk are crucial for root growth and salt tolerance in bermudagrass (Cynodon dactylon).

Salt stress is one of the major abiotic factors limiting the productivity of bermudagrass (Cynodon dactylon). However, the role of hormonal reprogramming and crosstalk in regulating root growth and salt tolerance in bermudagrass was not reported. Here, we examined the physiological and hormonal responses of two contrasting bermudagrass genotypes; 'C43,' salt-tolerant 'C198' salt-sensitive. Under salt stress, 'C43' had better membrane stability and higher photosynthetic activity than the 'C198.' Salt stress promoted root growth and improved root/shoot ratio and root activity in 'C43,' but the root growth of 'C198' was inhibited by salt stress, leading to diminished root activity. The two bermudagrass genotypes also showed critical differences in hormonal responses, especially in the roots. The root contents of indole-3-acetic acid (IAA), cytokinin derivatives, such as trans-zeatin riboside (tZR) and dihydrozeatin riboside (DHZR) were increased in 'C43,' but decreased in 'C198' when exposed to salt stress. The root growth rate was positively correlated with the root IAA, tZR and DHZR, indicating their crucial role in root growth under salt stress. The expressions of TAA/YUCCA and CYP735A involved in IAA and tZR biosynthesis were induced by salt stress in 'C43,' but inhibited in 'C198,' leading to reduced hormone accumulations. Salt stress decreased the iP, tZ, and DHZ content in the roots of both genotypes, and no significant difference was observed between the two genotypes. Salt stress reduced the content of GA3 in both genotypes by inhibiting GA20ox and GA2ox genes, which could be attributed to the reduced shoot growth in both genotypes. The increased ABA level by salt stress was significantly higher in 'C198' than 'C43.' Furthermore, there were positive and negative correlations between different hormones and root growth, suggesting that root growth could be regulated by complex hormonal reprogramming and crosstalk. This study provides a foundation for understanding the underlying mechanisms of hormonal-mediated root growth and salt tolerance in bermudagrass.

Identification of Cd-resistant microorganisms from heavy metal-contaminated soil and its potential in promoting the growth and Cd accumulation of bermudagrass.

Phytoremediation has been increasingly used as a green technology for the remediation of heavy metal contaminated soils. Microorganisms could enhance phytoremediation efficiency by solubilizing heavy metal and improve plant growth by producing phytohormones in the heavy metal contaminated soils. In this study, we investigated the abundance and composition of soil microbial communities in heavy metal contaminated soils. Furthermore, we identified a Cd-resistant fungal strain Penicillium janthinellum ZZ-2 and assessed its potential in improving plant growth, Cd accumulation and Cd tolerance in bermudagrass. The results indicated that long-term heavy metal pollution decreased microbial biomass and activity by inhibiting microbial community diversity, but did not significantly affect community composition. Mainly, the relative abundance of some specific bacterial and fungal taxa, such as Actinobacteria, Chloroflexi, Bacteroidetes, Ascomycota and Basidiomycota, changes under metal pollution. Furthermore, at genus level, certain microbial taxa, such as Pseudonocardiaceae, AD3, Latescibacteria, Apiotrichum and Paraboeremia, only exist in polluted soil. One Cd-resistant fungus ZZ-2 was isolated and identified as Penicillium janthinellum. Further characterization revealed that ZZ-2 had a greater capacity for Cd2+ absorption, produced indole-3-acid (IAA), and facilitated plant growth in the presence of Cd. Interestingly, ZZ-2 inoculation significantly increased Cd uptake in the stem and root of bermudagrass. Thus, ZZ-2 could improve plant growth under Cd stress by reducing Cd-toxicity, increasing Cd uptake and producing IAA. This study suggests a novel fungus-assisted phytoremediation approach to alleviate Cd toxicity in heavy metals contaminated soils.

Overexpression of FaHSP17.8-CII improves cadmium accumulation and tolerance in tall fescue shoots by promoting chloroplast stability and photosynthetic electron transfer of PSII.

Genetic improvement could play a significant role in enhancing the Cd accumulation, translocation and tolerance in plants. In this study, for the first time, we constructed transgenic tall fescue overexpressing a class II (CII) sHSP gene FaHSP17.8-CII, which enhanced Cd tolerance and the root-to-shoot Cd translocation. After exposed to 400 µM CdCl2, two FaHSP17.8-CII overexpressing lines (OE#3 and OE#7) exhibited 30% and 40% more shoot fresh weight, respectively, relative to the wild-type (WT). Both transgenic lines showed higher tolerance to Cd, as evidenced by lower levels of electrolyte leakage and malondialdehyde compared to the WT plants under Cd stress. FaHSP17.8-CII overexpression increased shoot Cd contents 49-59% over the WT plants. The Cd translocation factor of root-to-shoot in OE grasses was 69-85% greater than WT under Cd stress. Furthermore, overexpression of FaHSP17.8-CII reduced Cd-induced damages of chloroplast ultra-structure and chlorophyll synthesis, and then improved photosystem II (PSII) function under Cd stress, which resulted in less reactive oxygen species (ROS) accumulation in OE grasses than that in WT exposed to Cd stress. The study suggests a novel FaHSP17.8-CII-PSII-ROS module to understand the mechanisms of Cd detoxification and tolerance, which provides a new strategy to improve phytoremediation efficiency in Cd-stressed grasses.

Stress memory gene FaHSP17.8-CII controls thermotolerance via remodeling PSII and ROS signaling in tall fescue.

High temperature is the most limiting factor in the growth of cool-season turfgrass. To cope with high-temperature stress, grass often adopt a memory response by remembering one past recurring stress and preparing a quicker and more robust reaction to the next stress exposure. However, little is known about how stress memory genes regulate the thermomemory response in cool-season turfgrass. Here, we characterized a transcriptional memory gene, Fa-heat shock protein 17.8 Class II (FaHSP17.8-CII) in a cool-season turfgrass species, tall fescue (Festuca arundinacea Schreb.). The thermomemory of FaHSP17.8-CII continued for more than 4 d and was associated with a high H3K4me3 level in tall fescue under heat stress (HS). Furthermore, heat acclimation or priming (ACC)-induced reactive oxygen species (ROS) accumulation and photosystem II (PSII) electron transport were memorable, and this memory response was controlled by FaHSP17.8-CII. In the fahsp17.8-CII mutant generated using CRISPR/Cas9, ACC+HS did not substantially block the ROS accumulation, the degeneration of chloroplast ultra-structure, and the inhibition of PSII activity compared with HS alone. However, overexpression of FaHSP17.8-CII in tall fescue reduced ROS accumulation and chloroplast ultra-structure damage, and improved chlorophyll content and PSII activity under ACC+HS compared with that HS alone. These findings unveil a FaHSP17.8-CII-PSII-ROS module regulating transcriptional memory to enhance thermotolerance in cool-season turfgrass.

Simultaneous gene editing of three homoeoalleles in self-incompatible allohexaploid grasses.

Clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system has been widely used for precise gene editing in plants. However, simultaneous gene editing of multiple homoeoalleles remains challenging, especially in self-incompatible polyploid plants. Here, we simultaneously introduced targeted mutations in all three homoeoalleles of two genes in the self-incompatible allohexaploid tall fescue, using both CRISPR/Cas9 and LbCas12a (LbCpf1) systems. Loss-of-function mutants of FaPDS exhibited albino leaves, while knockout of FaHSP17.9 resulted in impaired heat resistance in T0 generation of tall fescue. Moreover, these mutations were inheritable. Our findings demonstrate the feasibility of generating loss-of-function mutants in T0 generation polyploid perennial grasses using CRISPR/Cas systems.

Genome-wide small RNA profiling reveals tiller development in tall fescue (Festuca arundinacea Schreb).

BACKGROUND: Tall fescue (Festuca arundinacea Schreb.) is a major cool-season forage and turfgrass species. The low tiller density and size dramatically limits its turf performance and forage yield. MicroRNAs (miRNA)-genes modules play critical roles in tiller development in plants. In this study, a genome-wide small RNA profiling was carried out in two tall fescue genotypes contrasting for tillering production ('Ch-3', high tiller production rate and 'Ch-5', low tiller production rate) and two types of tissue samples at different tillering development stage (Pre-tillering, grass before tillering; Tillering, grass after tillering). 'Ch-3', 'Ch-5', Pre-tillering, and Tillering samples were analyzed using high-throughput RNA sequencing. RESULTS: A total of 222 million high-quality clean reads were generated and 208 miRNAs were discovered, including 148 known miRNAs belonging to 70 families and 60 novel ones. Furthermore, 18 miRNAs were involved in tall fescue tiller development process. Among them, 14 miRNAs displayed increased abundance in both Ch-3 and Tillering plants compared with that in Ch-5 and Pre-tillering plants and were positive with tillering, while another four miRNAs were negative with tiller development. Out of the three miRNAs osa-miR156a, zma-miR528a-3p and osa-miR444b.2, the rest of 15 miRNAs were newfound and associated with tiller development in plants. Based on our previous full-length transcriptome analysis in tall fescue, 28,927 potential target genes were discovered for all identified miRNAs. Most of the 212 target genes of the 18 miRNAs were dominantly enriched into "ubiquitin-mediated proteolysis", "phagosome", "fatty acid biosynthesis", "oxidative phosphorylation", and "biosynthesis of unsaturated fatty acids" KEGG pathways. In addition, bdi-miR167e-3p targets two kinase proteins EIF2AK4 and IRAK4, and osa-miR397a targets auxin response factor 5, which may be the significant miRNA-genes controllers in tillering development. CONCLUSIONS: This is the first genome-wide miRNA profiles analysis to identify regulators involved in tiller development in cool-season turfgrass. Tillering related 18 miRNAs and their 212 target genes provide novel information for the understanding of the molecular mechanisms of miRNA-genes mediated tiller development in cool-season turfgrass.

Phytohormones-induced senescence efficiently promotes the transport of cadmium from roots into shoots of plants: A novel strategy for strengthening of phytoremediation.

Due to the long growth period of plants, phytoremediation is time costly. Improving the accumulation of cadmium (Cd) in shoots of plants will promote the efficiency of phytoremediation. In this study, two senescence-relative phytohormones, abscisic acid (ABA) and salicylic acid (SA), were applied to strengthening phytoremediation of Cd by tall fescue (Festuca arundinacea S.). Under hydroponic culture, phytohormones treatment increased the Cd content of shoots 11.4-fold over the control, reaching 316.3 mg/kg (dry weight). Phytohormones-induced senescence contributes to the transport of heavy metals, and HMA3 was found to play a key role in this process. Additionally, this strategy could strengthen the accumulation of Cu and Zn in tall fescue shoots. Moreover, in soil pot culture, the strategy increased shoot Cd contents 2.56-fold over the control in tall fescue, and 2.55-fold over the control in Indian mustard (Brassica juncea L.), indicating its comprehensive adaptability and potential use in the field. In summary, senescence-induced heavy metal transport is developed as a novel strategy to strengthen phytoremediation. The strategy could be applied at the end of phytoremediation with an additional short duration (7 days) with comprehensive adaptability, and markedly strengthen the phytoremediation in the field.

Exogenous salicylic acid ameliorates heat stress-induced damages and improves growth and photosynthetic efficiency in alfalfa (Medicago sativa L.).

Heat stress is found to be a detrimental factor for growth and development of alfalfa (Medicago sativa L.) which is tremendously invaluable forage due to its high feed value and yield potential. Salicylic acid (SA) has been reported to play a pivotal role in the regulation of plants biotic and abiotic stress response. However, the role of exogenous SA in protecting alfalfa from heat-induced damage has rarely been studied. In this study, four-week-old alfalfa seedlings were treated with 0.25 mM or 0.5 mM SA five days prior to high stress treatment (three day), and various growth and physiological traits were measured. The results showed that exogenous SA pretreatment could improve leaf morphology, plant height, biomass, chlorophyll content, and photosynthetic efficiency of alfalfa under heat stress. Meanwhile, SA could alleviate heat-induced membrane damage by reducing electrolyte leakage (EL) and malondialdehyde (MDA) content, and regulate the activities of antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). The results revealed that exogenous SA application enhanced alfalfa heat tolerance by modulating various morphological and physiological characteristics under heat stress, with more prominent effect at lower concentration (0.25 mM). Overall, this study provides fundamental insights into the SA-mediated physiological adaptation of alfalfa plants to heat stress, which could have useful implication in managing other plants which are suffering global warming.

Selenium supplementation alleviates cadmium-induced damages in tall fescue through modulating antioxidant system, photosynthesis efficiency, and gene expression.

Selenium (Se) is beneficial for plant growth under different stressful conditions. In this study, we investigated the protective effects of Se supply from Cd-induced damages in tall fescue under Cd stress. Tall fescue seedlings (40 days old) were treated with Cd (30 mg/L, as CdSO4·8/3 H2O) and Se (0.1 mg/L, as Na2SeO3) individually and in combination using 1/2 Hoagland's solution system for 7 days. Various physiological parameters, photosynthetic behaviors, and gene expressions were measured. The results showed that Cd-stressed plants displayed obvious toxicity symptoms such as leaf yellowing, decreasing plant height, and root length. Cd stress significantly increased the malondialdehyde (MDA) content and electrolyte leakage (EL), and remarkably reduced the chlorophyll and soluble protein content, antioxidant enzyme activities, and photosynthetic efficiency. Cd stress significantly inhibited the expression of two photosynthesis-related genes (psbB and psbC), but not psbA. In addition, it significantly inhibited the expression of antioxidant system-related genes such as ChlCu/ZnSOD, CytCu/ZnSOD, GPX, and pAPX, but significantly increased the expression of GR. However, Se improved the overall physiological and photosynthetic behaviors of Cd-stressed plants. Se significantly enhanced the chlorophyll and soluble protein content and CAT and SOD activities, but decreased MDA contents, EL, and Cd content and translocation in tall fescue under Cd stress. Furthermore, under Cd stress, Se increased the expression of psbA, psbB psbC, ChlCu/ZnSOD, CytCu/ZnSOD, GPx, and PAPx. The result suggests that Se alleviated the deleterious effects of Cd and improved Cd resistance in tall fescue through upregulating the antioxidant system, photosynthesis activities, and gene expressions.

Comparative physiological and metabolomic analyses reveal mechanisms of Aspergillus aculeatus-mediated abiotic stress tolerance in tall fescue.

Aspergillus aculeatus has been shown to stimulate plant growth, but its role in plants abiotic stress tolerance and the underlying mechanisms are not fully documented. In this study, we investigated the mechanisms of A.aculeatus-mediated drought, heat and salt stress tolerance in tall fescue. The results showed that A.aculeatus inoculation improved drought and heat stress tolerance in tall fescue as observed from its effect on turf quality (TQ) and leaf relative water content (LWC). In the same stress conditions, A.aculeatus alleviated reactive oxygen species (ROS) induced burst and cell damage, as indicated by lower H2O2, electrolyte leakage (EL) and malondialdehyde (MDA) levels. Additionally, the A.aculeatus inoculated plants exhibited higher photosynthetic efficiency than uninoculated plants under drought, heat and salt stress conditions. The fungus reduced the uptake of Na+, and inoculated plants showed lower Na+/K+, Na+/Ca2+and Na+/Mg2+ ratios compared to uninoculated ones under salt stress. Furthermore, comparative metabolomic analysis showed that A.aculeatus exclusively increased amino acid (such as proline and glycine) and sugar (such as glucose, fructose, sorbose, and talose) accumulation under drought and heat stress. However, there were no differences between inoculated and uninoculated plants except for changes in H2O2 level, Na+ in the root and photosynthetic efficiency under salt stress. Taken together, this study provides the first evidence of the protective roles of A.aculeatus in the tall fescue response to abiotic stresses, partially via protection of photosynthesis and modulation of metabolic homeostasis.

Transcriptome analysis reveals novel insights into the continuous cropping induced response in Codonopsis tangshen, a medicinal herb.

Codonopsis tangshen Oliv. (C. tangshen Oliv.), a famous medicinal herb in China, is seriously affected by continuous cropping (C-cro). The physiological and biochemical results indicated that C-cro significantly affected the malonaldehyde (MDA) and chlorophyll content, as well as activities of catalase (CAT) and superoxide dismutase (SOD) when compared with the non-continuous cropping (NC-cro) group. Transcriptome profiling found 762 differentially expressed genes, including 430 up-regulated and 332 down-regulated genes by C-cro. In addition, pathway enrichment analysis revealed that genes related to 'Tyrosine degradation I', 'Glycogen synthesis' and 'Phenylalanine and tyrosine catabolism' were up-regulated, and genes associated with 'Signal transduction', 'Immune system', etc. were down-regulated by C-cro. The expression of target genes was further validated by Q-PCR. In this study, we demonstrated the effects of C-cro on C. tangshen at the transcriptome level, and found possible C-cro responsive candidate genes. These findings could be further beneficial for improving the continuous cropping tolerance.

Characterization of the Cd-resistant fungus Aspergillus aculeatus and its potential for increasing the antioxidant activity and photosynthetic efficiency of rice.

Considerable evidence exists that microorganisms play a significant role in the remediation of soil contaminated with heavy metals. Aspergillus aculeatus (A. aculeatus) isolated from Cd-polluted soil has been shown to increase the tolerance of turfgrasses to Cd stress. In this study, we assessed the tolerance, biosorption capacity for Cd and surface characteristics of this fungus and investigated the effect of plant inoculation with A. aculeatus on the lipid peroxidation, antioxidant activities and photosynthetic rates in rice cultivated in Cd-contaminated soil. The results indicated that the removal efficiency of A. aculeatus was 46.8% at a Cd concentration of 10 mg L-1. The A. aculeatus strains had the capacity to produce indole acetic acid, siderophore, and 1-aminocyclopropane-1-carboxylate deaminase and to solubilize phosphate. The O2- accumulation and the amount of MDA in rice roots inoculated with A. aculeatus were significantly lower than those in uninoculated plants. Nevertheless, no decrease in leaf ROS accumulation and photosynthetic activity was observed between the inoculated and uninoculated plants. Inoculation with A. aculeatus contained more of the ROS-scavenging metabolite GSH, a higher GSH/GSSG ratio, and higher antioxidative enzyme (SOD, POD, and CAT) activities, possibly explaining the lower ROS concentrations observed in inoculated roots in the presence of Cd. These results suggest that application of A. aculeatus has the potential to protect crops against Cd stress.