A nonspecific lipid transfer protein, StLTP10, mediates resistance to Phytophthora infestans in potato.

Nonspecific lipidtransfer proteins (nsLTPs), which are small, cysteine-rich proteins, belong to the pathogenesis-related protein family, and several of them act as positive regulators during plant disease resistance. However, the underlying molecular mechanisms of these proteins in plant immune responses are unclear. In this study, a typical nsLTP gene, StLTP10, was identified and functionally analysed in potato. StLTP10 expression was significantly induced by Phytophthora infestans, which causes late blight in potato, and defence-related phytohormones, including abscisic acid (ABA), salicylic acid, and jasmonic acid. Characterization of StLTP10-overexpressing and knockdown lines indicated that StLTP10 positively regulates plant resistance to P. infestans. This resistance was coupled with enhanced expression of reactive oxygen species scavenging- and defence-related genes. Furthermore, we identified that StLTP10 physically interacts with ABA receptor PYL4 and affects its subcellular localization. These two proteins work together to regulate stomatal closure during pathogen infection. Interestingly, we also found that wound-induced protein kinase interacts with StLTP10 and positively regulates its protein abundance. Taken together, our results provide insight into the role of StLTP10 in resistance to P. infestans and suggest candidates to enhance broad-spectrum resistance to pathogens in potato.

Purification and antioxidant capacity analysis of anthocyanin glucoside cinnamic ester isomers from Solanum nigrum fruits.

In a recent study, anthocyanins, which have a strong free radical-scavenging activity, were examined for their potential to effectively prevent cancer. However, clinical trials are limited by the purity of the anthocyanin. Multiple methods are used to extract and purify anthocyanins. Based on previous work on Solanum nigrum, which is a widely distributed plant, in this study, DM130 macroporous resin, Sephadex LH20, and a C18 column were used to separate cis-trans anthocyanin isomers. These anthocyanins constitute the majority of total S. nigrum anthocyanins. The results showed that this "DM130-LH20-C18 system" can be used to obtain a cinnamic acid-derived cis-trans anthocyanin, petunidin-3-(p-coumaroyl)-rutinoside-5-glucoside, with a purity of 98.5%, for effective quantitation. In order to determine the antioxidant ability of the petunidin-3-(p-coumaroyl)-rutinoside-5-glucoside cis-trans isomers, three ordinary methods were adopted. The maximum antioxidant ability of the cis-trans anthocyanin was dozens of times higher than that of vitamin C.

Copper ions suppress abscisic acid biosynthesis to enhance defence against Phytophthora infestans in potato.

Copper-based antimicrobial compounds are widely and historically used to control plant diseases, such as late blight caused by Phytophthora infestans, which seriously affects the yield and quality of potato. We previously identified that copper ion (Cu2+ ) acts as an extremely sensitive elicitor to induce ethylene (ET)-dependent immunity in Arabidopsis. Here, we found that Cu2+ induces the defence response to P. infestans in potato. Cu2+ suppresses the transcription of the abscisic acid (ABA) biosynthetic genes StABA1 and StNCED1, resulting in decreased ABA content. Treatment with ABA or inhibitor fluridone made potato more susceptible or resistance to late blight, respectively. In addition, potato with knockdown of StABA1 or StNCED1 showed greater resistance to late blight, suggesting that ABA negatively regulates potato resistance to P. infestans. Cu2+ also promotes the rapid biosynthesis of ET. Potato plants treated with 1-aminocyclopropane-1-carboxylate showed enhanced resistance to late blight. Repressed expression of StEIN2 or StEIN3 resulted in enhanced transcription of StABA1 and StNCED1, accumulation of ABA and susceptibility to P. infestans. Consistently, StEIN3 directly binds to the promoter regions of StABA1 and StNCED1. Overall, we concluded that Cu2+ triggers the defence response to potato late blight by activating ET biosynthesis to inhibit the biosynthesis of ABA.

Arbuscular mycorrhizal fungi (AMF) enhanced the growth, yield, fiber quality and phosphorus regulation in upland cotton (Gossypium hirsutum L.).

We previously reported on the strong symbiosis of AMF species (Rhizophagus irregularis CD1) with the cotton (Gossypium hirsutum L.) which is grown worldwide. In current study, it was thus investigated in farmland to determine the biological control effect of AMF on phosphorus acquisition and related gene expression regulation, plant growth and development, and a series of agronomic traits associated with yield and fiber quality in cotton. When AMF and cotton were symbiotic, the expression of the specific phosphate transporter family genes and P concentration in the cotton biomass were significantly enhanced. The photosynthesis, growth, boll number per plant and the maturity of the fiber were increased through the symbiosis between cotton and AMF. Statistical analysis showed a highly significant increase in yield for inoculated plots compared with that from the non inoculated controls, with an increase percentage of 28.54%. These findings clearly demonstrate here the benefits of AMF-based inoculation on phosphorus acquisition, growth, seed cotton yield and fiber quality in cotton. Further improvement of these beneficial inoculants on crops will help increase farmers' income all over the world both now and in the future.

Transgenic RXLR Effector PITG_15718.2 Suppresses Immunity and Reduces Vegetative Growth in Potato.

Phytophthora infestans causes the severe late blight disease of potato. During its infection process, P. infestans delivers hundreds of RXLR (Arg-x-Leu-Arg, x behalf of any one amino acid) effectors to manipulate processes in its hosts, creating a suitable environment for invasion and proliferation. Several effectors interact with host proteins to suppress host immunity and inhibit plant growth. However, little is known about how P. infestans regulates the host transcriptome. Here, we identified an RXLR effector, PITG_15718.2, which is upregulated and maintains a high expression level throughout the infection. Stable transgenic potato (Solanum tuberosum) lines expressing PITG_15718.2 show enhanced leaf colonization by P. infestans and reduced vegetative growth. We further investigated the transcriptional changes between three PITG_15718.2 transgenic lines and the wild type Désirée by using RNA sequencing (RNA-Seq). Compared with Désirée, 190 differentially expressed genes (DEGs) were identified, including 158 upregulated genes and 32 downregulated genes in PITG_15718.2 transgenic lines. Eight upregulated and nine downregulated DEGs were validated by real-time RT-PCR, which showed a high correlation with the expression level identified by RNA-Seq. These DEGs will help to explore the mechanism of PITG_15718.2-mediated immunity and growth inhibition in the future.

Transcriptome-Wide Identification and Characterization of Potato Circular RNAs in Response to Pectobacterium carotovorum Subspecies brasiliense Infection.

Little information about the roles of circular RNAs (circRNAs) during potato-Pectobacterium carotovorum subsp. brasiliense (Pcb) interaction is currently available. In this study, we conducted the systematic identification of circRNAs from time series samples of potato cultivars Valor (susceptible) and BP1 (disease tolerant) infected by Pcb. A total of 2098 circRNAs were detected and about half (931, 44.38%) were intergenic circRNAs. And differential expression analysis detected 429 significantly regulated circRNAs. circRNAs play roles by regulating parental genes and sponging miRNAs. Gene Ontology (GO) enrichment of parental genes and miRNAs targeted mRNAs revealed that these differentially expressed (DE) circRNAs were involved in defense response (GO:0006952), cell wall (GO:0005199), ADP binding (GO:0043531), phosphorylation (GO:0016310), and kinase activity (GO:0016301), suggesting the roles of circRNAs in regulating potato immune response. Furthermore, weighted gene co-expression network analysis (WGCNA) found that circRNAs were closely related with coding-genes and long intergenic noncoding RNAs (lincRNAs). And together they were cultivar-specifically regulated to strengthen immune response of potato to Pcb infection, implying the roles of circRNAs in reprogramming disease responsive transcriptome. Our results will provide new insights into the potato-Pcb interaction and may lead to novel disease control strategy in the future.

Identification of Anthocyanin Composition and Functional Analysis of an Anthocyanin Activator in Solanum nigrum Fruits.

Solanum nigrum fruits have been conventionally used in beverages due to their nutritional substances such as minerals, vitamins, amino acids, proteins, sugars, polyphenols, and anthocyanins. The characterization of components and regulatory mechanism of anthocyanins in S. nigrum fruits have rarely been reported. In this study, we determined that the peel and flesh of S. nigrum fruits shared similar HPLC profiles but different contents and total antioxidant activities for anthocyanins. After an efficient purification method, mainly including extraction with pH 1.0 distilled water and then desorption with pH 1.0 95% ethanol after a DM-130 resin adsorption step to obtain more pure anthocyanin extracts, the purity of anthocyanins extracted from S. nigrum fruits reached 56.1%. Moreover, eight anthocyanins from S. nigrum fruit were identified with HPLC-MS/MS for the first time. A typical R2R3-MYB transcription factor gene, SnMYB, was also cloned for the first time by rapid amplification of cDNA ends (RACE)-PCR from S. nigrum. Moreover, the contents of anthocyanins were shown to correlate well (r = 0.93) with the expression levels of SnMYB gene during the fruit's developmental stages. Most significantly, SnMYB gene successfully produced high anthocyanin content (1.03 mg/g) when SnMYB gene was transiently expressed in tobacco leaves. Taken together, S. nigrum fruits are a promising resource for anthocyanin extraction, and SnMYB gene is an activator that positively regulates anthocyanin biosynthesis in S. nigrum.

Development of Marker-Free Transgenic Potato Tubers Enriched in Caffeoylquinic Acids and Flavonols.

Potato (Solanum tuberosum L.) is a major crop worldwide that meets human economic and nutritional requirements. Potato has several advantages over other crops: easy to cultivate and store, cheap to consume, and rich in a variety of secondary metabolites. In this study, we generated three marker-free transgenic potato lines that expressed the Arabidopsis thaliana flavonol-specific transcriptional activator AtMYB12 driven by the tuber-specific promoter Patatin. Marker-free potato tubers displayed increased amounts of caffeoylquinic acids (CQAs) (3.35-fold increases on average) and flavonols (4.50-fold increase on average). Concentrations of these metabolites were associated with the enhanced expression of genes in the CQA and flavonol biosynthesis pathways. Accumulation of CQAs and flavonols resulted in 2-fold higher antioxidant capacity compared to wild-type potatoes. Tubers from these marker-free transgenic potatoes have therefore improved antioxidant properties.

[Effects of deguelin on proliferation and apoptosis of MCF-7 breast cancer cells by phosphatidylinositol 3-kinase/Akt signaling pathway].

OBJECTIVE: To study the effects of deguelin on proliferation and apoptosis of human breast cancer cell line MCF-7 and on phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. METHODS: After treatment with 0, 1, 5, 10, 15 and 20 µmol/L of deguelin for 6, 24, 48 and 72 hours, the proliferation inhibition rate of MCF-7 cells was measured by cell counting kit-8 assay. Apoptosis rate of MCF-7 cells was detected with Annexin V-fluorescein isothiocyanate/propidium iodide double staining by flow cytometry and the apoptotic morphology was observed under a transmission electron microscope. After treatment with 0, 1 and 5 µmol/L of deguelin for 6 hours, 5 proteins involved in the PI3K/Akt signaling pathway were examined by Western blot analysis. RESULTS: Deguelin at doses of 5, 10, 15 and 20 µmol/L inhibited the proliferation of MCF-7 cells at 6, 24, 48 and 72 hours. There was a significant difference in each group compared with the control group (P<0.01). The inhibitory effect was more marked with increasing concentration and duration of treatment. There were statistical differences (P<0.05) among 5, 10, 15 and 20 µmol/L groups. However, 1 µmol/L of deguelin had no obvious effects on the proliferation of MCF-7 cells at 6, 24, 48 and 72 hours, showing no significant difference compared with control group (P>0.05). Deguelin at doses of 5, 10, 15 and 20 µmol/L induced apoptosis of MCF-7 cells at 6 hours. There were significant differences (P<0.01) in the early and late apoptosis rate between the treated groups and the control group. The typical apoptotic MCF-7 cells were observed under the transmission electron microscopy. However, 1 µmol/L of deguelin had no apparent effect in inducing apoptosis of MCF-7 cells at 6 hours. After treatment with 5 µmol/L of deguelin for 6 hours the expression of phosphorylated phosphatase and tensin homologue deleted on chromosome 10 (PTEN) (Ser380), phosphorylated 3-phosphoinositide-dependent protein kinase 1 (PDK1) (Ser241), phosphorylated Akt (Thr308) and phosphorylated glycogen synthase kinase-3ß (GSK-3ß) (Ser9) proteins were significantly reduced in MCF-7 cells, while there was no significant change in the expression of total Akt protein. However, after treatment with 1 µmol/L of deguelin for 6 hours, there was no apparent change in the expression of these 5 proteins. CONCLUSION: Deguelin can inhibit the phosphorylation of GSK-3ß (Ser9) via inhibition of the phosphorylation of PTEN (Ser380) and PDK1 (Ser241) pathway, thus inducing apoptosis and inhibiting proliferation of MCF-7 cells.

Promoter mutations of an essential gene for pollen development result in disease resistance in rice.

Disease resistance and sexual reproductive development are generally considered as separate biological processes, regulated by different sets of genes. Here we show that xa13, a recessive allele conferring disease resistance against bacterial blight, one of the most devastating rice diseases worldwide, plays a key role in both disease resistance and pollen development. The dominant allele, Xa13, is required for both bacterial growth and pollen development. Promoter mutations in Xa13 cause down-regulation of expression during host-pathogen interaction, resulting in the fully recessive xa13 that confers race-specific resistance. The recessive xa13 allele represents a new type of plant disease resistance.