•AMF protects Leymus chinensis seedlings against salt-alkali stress.•Growth and photosynthesis can be enhanced by AM.•Excessive nitrogen inhibits the growth and photosynthetic ability of seedlings.Leymus chinensis is the most promising grass species for salt-alkaline grassland restoration in northern China. However, little information exists concerning the role of arbuscular mycorrhizal (AM) symbiosis in the adaptation of seedlings to salt-alkali stress, particularly under increased nitrogen deposition, which has become a major environmental problem throughout the world. In this study, Leymus chinensis seedlings were cultivated in soil with 0, 100 and 200 mM NaCl/NaHCO3 under two forms of nitrogen (10 mM NH4NO3 or NH4Cl: NH4NO3 = 3:1), and the root colonization, growth and photosynthetic characteristics of the seedlings were measured. The results showed that the colonization rate and intensity decreased with increasing salt-alkali stress and were much lower under alkali stress. The nitrogen treatments also decreased the colonization, particularly under the NH4+-N treatment. Compared with the non-mycorrhizal controls, mycorrhizal seedlings generally presented higher plant biomass, photosynthetic parameters and contents of photosynthetic pigments under stresses, and the inhibitive effects of alkali stress were substantially stronger. In addition, both nitrogen forms decreased the physiological indexes compared with those of the AM seedlings. Our results suggest that salt stress and alkali stress are significantly different and that the salt-alkali tolerance of Leymus chinensis seedlings could be enhanced by associations with arbuscular mycorrhizal fungi, in which would yield better plant growth and photosynthesis. Excessive nitrogen in the soil affects mycorrhizal colonization and thereby inhibits the growth and photosynthetic ability of the seedlings.Download high-res image (191KB)Download full-size image

Cerasomes, a novel type of organic–inorganic liposomal nanohybrid with a silicate surface, has attracted a great deal of attention as a perfect substitute for liposomes due to its good morphological stability. In this paper, the capability of cerasomes as possible carriers for 10-hydroxycamptothecin (HCPT) delivery was investigated. Both cerasomes and composite cerasomes containing liposome-forming lipids (LFLs) were fabricated to evaluate their potential for the release of HCPT. It was found that composite cerasomes exhibited good encapsulation efficiency and a high loading content of HCPT compared with cerasomes. They also displayed a remarkable ability to maintain their size and optimize the release rate of HCPT, resulting in an improved drug pharmacokinetic profile in vivo. In vivo toxicity experiments showed that Wistar rats administered with cerasomes at a high dose of 50 mg kg−1 displayed slight acute toxicity at 24 h; afterwards, the rats recovered from the side effects. No visualized tissue injury was found during the experimental period. All the results indicated that liposomal nanohybrid cerasomes may be a type of promising drug delivery platform for the sustained release of the anticancer drug HCPT in vivo.

Camptotheca acuminate plant is an important phytomedicinal species that contains camptothecin (CPT), a natural pentacyclic indole alkaloid. This study was aimed at the effect of arbuscular mycorrhiza (AM) development on the accumulation and location of this metabolite in C. acuminate seedling roots. Autofluorescence of CPT shows the localization of CPT in mycorrhizal roots. We examined CPT level in response to AM development in C. acuminate roots by the combination of confocal laser scanning microscopy and spontaneous fluorescence of CPT. CPT was specifically localized around AM fungi in AM roots of C. acuminate, and the level of CPT rose with increasing colonization of roots with AM fungi. The accumulation and localization of CPT was directly correlated with the formation and development of AM in C. acuminate roots.

•Neutral pentacyclic triterpenes such as betulin cannot be easily ionized by ESI.•Betulin reacted with PTSI and generated an ionizable and fragmentable derivative.•A LC–ESI/MS/MS method for the quantification of betulin in rat plasma was developed.•The LC–MS/MS method was applied to the pharmacokinetic study of betulin in rats.Neutral pentacyclic triterpenes with only one or two hydroxyl groups, such as betulin, are not easily ionized by electrospray ionization (ESI). However, because betulin is reactive and neutral, derivatization may improve ionization efficiency. In the present study, the potency of different derivatization reagents was evaluated and p-toluenesulfonyl isocyanate (PTSI) was proven to be the optimal. The derivative generated by the reaction of betulin with PTSI was ionizable and fragmentable in the negative mode by liquid chromatography–electrospray ionization/tandem mass spectrometry (LC–ESI/MS/MS). Based on this chemical derivatization, an LC–ESI/MS/MS method was developed and validated for the quantification of betulin in rat plasma. The sample was extracted with ethyl acetate, derivatized with PTSI, separated on an ACQ UPLC BEH phenyl column, and analyzed in negative multiple reaction monitoring (MRM) mode. The calibration curve was linear over the betulin concentration range 2.5–200 ng/mL. The lower limit of quantification was 2.5 ng/mL. The inter- and intra-day accuracy and precision were within ±15%. Betulin recoveries were 86.7% or higher at three quality control levels (5, 50, and 160 ng/mL). This validated method was subsequently applied to a pharmacokinetic study of betulin in rat plasma after oral administration.

Naturally occurring camptothecin (CPT) is an important source of chemotherapeutic agents. The extraction from Camptotheca acuminata is still the main approach to obtain CPT compared with total synthesis. In the present study, ultrasound-assisted extractions (UAE) of CPT from C. acuminata seeds with alkaline solutions were investigated and CPT yield were determined by High Performance Liquid Chromatography. The conditions of alkaline species and concentrations, extraction time, extraction temperature and ultrasonic power were optimized. Results show that both Na3PO4 and Na2CO3 solutions gain good extraction yields, whereas Na3PO4 solution has stronger basicity and need higher concentration than Na2CO3 solution does, thus aqueous Na2CO3 is more beneficial for the extraction. The optimal condition was ultrasonically extracted with 0.5% aqueous Na2CO3 at 50°C and ultrasonic power of 400 W for 60 min. Comparing with UAE with ethanol, the extraction with 0.5% Na2CO3 solution achieves higher yield. Moreover, aqueous Na2CO3 as a solvent has various advantages including non-toxicity, inflammable, non-corrosive and low cost, which ensure this UAE method is a superior method with high utilizing prospect.

Salinity is a major abiotic stress affecting plant cultivation and productivity. Thellungiella halophila is a halophyte and has been used as a model for studying plant salt tolerance. Understanding the molecular mechanisms of salinity tolerance will facilitate the generation of salt tolerant crops. Here we report comparative leaf proteomics of Arabidopsis, a glycophyte, and its close relative Thellungiella, a halophyte, under different salt stress conditions. Proteins from control and NaCl treated Arabidopsis and Thellungiella leaf samples were extracted and separated by two-dimensional gel electrophoresis. A total of 88 protein spots from Arabidopsis gels and 37 protein spots from Thellungiella gels showed significant changes. Out of these spots, a total of 79 and 32 proteins were identified by mass spectrometry in Arabidopsis and Thellungiella, respectively. Most of the identified proteins were involved in photosynthesis, energy metabolism, and stress response in Arabidopsis and Thellungiella. As a complementary approach, isobaric tag for relative and absolute quantification (iTRAQ) LC−MS was used to identify crude microsomal proteins. A total of 31 and 32 differentially expressed proteins were identified in Arabidopsis and Thellungiella under salt treatment, respectively. Overall, there were more proteins changed in abundance in Arabidopsis than in Thellungiella. Distinct patterns of protein changes in the two species were observed. Collectively, this work represents the most extensive proteomic description of salinity responses of Arabidopsis and Thellungiella and has improved our knowledge of salt tolerance in glycophytes and halophytes.

Jasmonates (JAs) are the well characterized fatty acid-derived cyclopentanone signals involved in the plant response to biotic and abiotic stresses. JAs have been shown to regulate many aspects of plant metabolism, including glucosinolate biosynthesis. Glucosinolates are natural plant products that function in defense against herbivores and pathogens. In this study, we applied a proteomic approach to gain insight into the physiological processes, including glucosinolate metabolism, in response to methyl jasmonate (MeJA). We identified 194 differentially expressed protein spots that contained proteins that participated in a wide range of physiological processes. Functional classification analysis showed that photosynthesis and carbohydrate anabolism were repressed after MeJA treatment, while carbohydrate catabolism was up-regulated. Additionally, proteins related to the JA biosynthesis pathway, stress and defense, and secondary metabolism were up-regulated. Among the differentially expressed proteins, many were involved in oxidative tolerance. The results indicate that MeJA elicited a defense response at the proteome level through a mechanism of redirecting growth-related metabolism to defense-related metabolism.