Antifeedant and insecticidal effects of mandelic acid on the brown planthopper Nilaparvata lugens Stål

To study the effects of mandelic acid (MA) on the brown planthopper (BPH), Nilaparvata lugens, the survival rate and behaviour of BPH fed on an artificial diet with different dosages of MA was observed. The survival rate of BPH decreased with the increase of the MA concentration and feeding time. In contrast to the control, the survival rate of BPH 72 h after feeding decreased significantly. Electrical penetration graph (EPG) data indicated that MA absorbed by the rice plant from Kimura B solution significantly affected the feeding behaviour of BPH. At the concentrations of 0.1, 0.5, and 1.0 mg/ml, duration of the phloem ingestion of BPH decreased from 115.34 min (control) to 30.41, 7.63, and 0.36 min, respectively. Periods of xylem ingestion of MA-treated BPH were significantly shorter than those of the control (50.44 min). Moreover, BPH spent more time walking around or being at rest on MA-treated rice plants, as well as in stylet activities. The GST (glutathione S-transferase) activity of BPH increased with the increasing MA concentration, while the GPX (glutathione peroxidases) activity did not change significantly. The results indicate that MA has an antifeedant and insecticidal effect on BPH.     

Maslinic acid protects vascular smooth muscle cells from oxidative stress through Akt/Nrf2/HO-1 pathway

Maslinic acid (MA) is a natural triterpenoid widely distributed in edible and medicinal plants and has been demonstrated to possess bioactivity. However, its effect on vascular smooth muscle cells (VSMC) has not been explored yet. In this study, we found that heme oxygenase-1 (HO-1) expression was increased in VSMCs treated with MA. Furthermore, MA was found to induce Akt activation in a dose- and time-dependent manner. Wortmannin suppression of Akt was able to abolish HO-1 upregulation in VSMCs, suggesting the requirement of Akt activation for MA effect on HO-1. Further investigation indicated that Akt activation resulted in the elevated expression of Nrf2, a HO-1 promoter, in MA-treated VMSCs. Finally, we found that MA was able to protect VSMCs from oxidative stress induced by H₂O₂. Blocking the activation of Akt/Nrf2/HO-1 was able to compromise the protective effect of MA on VSMCs. Collectively, we provided evidence that MA protected VMSCs from oxidative stress through Akt/Nrf2/HO-1 pathway.     

基于植物-土壤反馈的不同绿肥驯化微生物对玉米生长的影响

【背景】在农田生态系统中,土壤微生物与植物互作的机制仍不清楚。【目的】进一步加强对植物-微生物互作的认识,筛选出引起不同反馈作用的关键微生物或微生物类群。【方法】采集豆科绿肥救荒野豌豆(Vicia sativa, V)、十字花科绿肥油菜(Brassica napus, N)和荒坡土壤(remnant prairie, R)驯化的田块土壤0-20 cm作为菌剂在温室进行植物-土壤反馈(plant-soil feedback,PSF)试验。土壤菌剂的接种量为10%,即有90%理化性质一致的灭菌土壤作为背景土,同时设置灭菌土壤菌剂作为对照(CK),种植玉米。每组土壤菌剂处理均分为50 mg/kg高磷(high phosphorus,HP)和5 mg/kg低磷(low phosphorus, LP)两个磷浓度处理。玉米收获后,测定产量和植株地上部磷含量,并取土壤样品进行高通量测序,解析不同养分供给情况下微生物对作物生长的反馈效应。【结果】高磷和土壤反馈效应均促进了玉米的生长。在低磷水平下,V、N和R处理的玉米地上部生物量均高于CK处理,但N处理的玉米地上部生物量增加最多(38%),且增幅显著高...     

Key factors identified by proteomic analysis in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) seedlings’ response to long-term exposure to different phosphate levels

Background

Maize seedlings are constantly exposed to inorganic phosphate (Pi)-limited environments. To understand how maize cope with low Pi (LP) and high Pi (HP) conditions, physiological and global proteomic analysis of QXN233 genotype were performed under the long-term Pi starvation and supplementation.

Methods

We investigated the physiological response of QXN233 genotype to LP and HP conditions and detected the changes in ion fluxes by non-invasive micro-test technology and gene expression by quantitative real-time polymerase chain reaction. QXN233 was further assessed using vermiculite assay, and then proteins were isolated and identified by nano-liquid chromatography-mass spectrometry.

Results

A negative relationship was observed between Na⁺ and Pi, and Na⁺ efflux was enhanced under HP condition. Furthermore, a total of 681 and 1374 were identified in the leaves and roots, respectively, which were mostly involved in metabolism, ion transport, and stress response. Importantly, several key Pi transporters were identified for breeding potential. Several ion transporters demonstrated an elaborate interplay between Pi and other ions, together contributing to the growth of QXN233 seedlings.

Conclusion

The results from this study provide insights into the response of maize seedlings to long-term Pi exposure.

     

Involvement of OsPht1;4 in phosphate acquisition and mobilization facilitates embryo development in rice

Phosphate (Pi) transporters mediate acquisition and transportation of Pi within plants. Here, we investigated the functions of OsPht1;4 (OsPT4), one of the 13 members of the Pht1 family in rice. Quantitative real‐time RT‐PCR analysis revealed strong expression of OsPT4 in roots and embryos, and OsPT4 promoter analysis using reporter genes confirmed these findings. Analysis using rice protoplasts showed that OsPT4 localized to the plasma membrane. OsPT4 complemented a yeast mutant defective in Pi uptake, and also facilitated increased accumulation of Pi in Xenopus oocytes. Further, OsPT4 genetically modified (GM) rice lines were generated by knockout/knockdown or over‐expression of OsPT4. Pi concentrations in roots and shoots were significantly lower and higher in knockout/knockdown and over‐expressing plants, respectively, compared to wild‐type under various Pi regimes. ³³Pi uptake translocation assays corroborated the altered acquisition and mobilization of Pi in OsPT4 GM plants. We also observed effects of altered expression levels of OsPT4 in GM plants on the concentration of Pi, the size of the embryo, and several attributes related to seed development. Overall, our results suggest that OsPT4 encodes a plasma membrane‐localized Pi transporter that facilitates acquisition and mobilization of Pi, and also plays an important role in development of the embryo in rice.     

Overexpression of Thellungiella halophila H(+)-pyrophosphatase Gene Improves Low Phosphate Tolerance in Maize

Low phosphate availability is a major constraint on plant growth and agricultural productivity. Engineering a crop with enhanced low phosphate tolerance by transgenic technique could be one way of alleviating agricultural losses due to phosphate deficiency. In this study, we reported that transgenic maize plants that overexpressed the Thellungiella halophila vacuolar H(+)-pyrophosphatase gene (TsVP) were more tolerant to phosphate deficit stress than the wild type. Under phosphate sufficient conditions, transgenic plants showed more vigorous root growth than the wild type. When phosphate deficit stress was imposed, they also developed more robust root systems than the wild type, this advantage facilitated phosphate uptake, which meant that transgenic plants accumulated more phosphorus. So the growth and development in the transgenic maize plants were not damaged as much as in the wild type plants under phosphate limitation. Overexpression of TsVP increased the expression of genes involved in auxin transport, which indicated that the development of larger root systems in transgenic plants might be due in part to enhanced auxin transport which controls developmental events in plants. Moreover, transgenic plants showed less reproductive development retardation and a higher grain yield per plant than the wild type plants when grown in a low phosphate soil. The phenotypes of transgenic maize plants suggested that the overexpression of TsVP led to larger root systems that allowed transgenic maize plants to take up more phosphate, which led to less injury and better performance than the wild type under phosphate deficiency conditions. This study describes a feasible strategy for improving low phosphate tolerance in maize and reducing agricultural losses caused by phosphate deficit stress.     

Rice ACID PHOSPHATASE 1 regulates Pi stress adaptation by maintaining intracellular Pi homeostasis

The concentration and homeostasis of intracellular phosphate (Pi) are crucial for sustaining cell metabolism and growth. During short-term Pi starvation, intracellular Pi is maintained relatively constant at the expense of vacuolar Pi. After the vacuolar stored Pi is exhausted, the plant cells induce the synthesis of intracellular acid phosphatase (APase) to recycle Pi from expendable organic phosphate (Po). In this study, the expression, enzymatic activity and subcellular localization of ACID PHOSPHATASE 1 (OsACP1) were determined. OsACP1 expression is specifically induced in almost all cell types of leaves and roots under Pi stress conditions. OsACP1 encodes an acid phosphatase with broad Po substrates and localizes in the endoplasmic reticulum (ER) and Golgi apparatus (GA). The phylogenic analysis demonstrates that OsACP1 has a similar structure with human acid phosphatase PHOSPHO1. Overexpression or mutation of OsACP1 affected Po degradation and utilization, which further influenced plant growth and productivity under both Pi-sufficient and Pi-deficient conditions. Moreover, overexpression of OsACP1 significantly affected intracellular Pi homeostasis and Pi starvation signalling. We concluded that OsACP1 is an active acid phosphatase that regulates rice growth under Pi stress conditions by recycling Pi from Po in the ER and GA.     

Large-Scale Evaluation of Maize Germplasm for Low-Phosphorus Tolerance

Low-phosphorus (LP) stress is a global problem for maize production and has been exacerbated by breeding activities that have reduced the genetic diversity of maize. Although LP tolerance in maize has been previously evaluated, the evaluations were generally performed with only a small number of accessions or with samples collected from a limited area. In this research, 826 maize accessions (including 580 tropical/subtropical accessions and 246 temperate accessions) were evaluated for LP tolerance under field conditions in 2011 and 2012. Plant height (PH) and leaf number were measured at three growth stages. The normalized difference vegetation index (NDVI) and fresh ear weight (FEW) were also measured. Genetic correlation analysis revealed that FEW and NDVI were strongly correlated with PH, especially at later stages. LP-tolerant and -sensitive accessions were selected based on the relative trait values of all traits using principal component analysis, and all the 14 traits of the tolerant maize accessions showed less reduction than the sensitive accessions under LP conditions. LP tolerance was strongly correlated with agronomic performance under LP stress conditions, and both criteria could be used for genetic analysis and breeding of LP tolerance. Temperate accessions showed slightly better LP tolerance than tropical/subtropical ones, although more tolerant accessions were identified from tropical/subtropical accessions, which could be contributed by their larger sample size. This large-scale evaluation provides useful information, LP-tolerant germplasm resources and evaluation protocol for genetic analysis and developing maize varieties for LP tolerance.