Passion fruit (Passiflora edulis Sims) is a vine of the Passiflora genus in the Passifloraceae family.  The extracted components include flavonoids and terpenoids, which have good anti-anxiety and anti-inflammatory effects in humans.  In this study, we analyzed the transcriptomes of four tissues of the ‘Zixiang’ cultivar using RNA-Seq, which provided a dataset for functional gene mining.  The de novo assembly of these reads generated 96 883 unigenes, among which 61 022 unigenes were annotated (62.99% yield).  In addition to its edible value, another important application of passion fruit is its medicinal value.  The flavonoids and terpenoids are mainly derivatives of luteolin, apigenin, cycloartane triterpenoid saponins and other active substances in leaf extracts.  A series of candidate unigenes in the transcriptome data that are potentially involved in the flavonoid and terpenoid synthesis pathways were screened using homology-based BLAST and phylogenetic analysis.  The results showed that the biosynthesis of triterpenoids in passion fruit comes from the branches of the mevalonate (MVA) and 2-C-methyl-D-erythritol 4-phosphate/1-deoxy-D-xylulose 5-phosphate (MEP/DOXP) pathways, which is different from the MVA pathway that is used in other fruit trees.  Most of the candidate genes were found to be highly expressed in the leaves and/or flowers.  Quantitative real-time PCR (qRT-PCR) verification was carried out and confirmed the reliability of the RNA-Seq data.  Further amplification and functional analysis of these putative unigenes will provide additional insight into the biosynthesis of flavonoids and terpenoids in passion fruit.

Streptococcus equi subsp. zooepidemicus (SEZ) is an important zoonotic agent.  Here, a virulence-attenuated strain M35246 derived from natural variation of wild-type SEZ ATCC35246 was found.  M35246 showed a deletion of 25 contiguous genes as well as a loss-of-function mutation in covS.  Subsequently, a 25-gene-deleted strain (ΔPI), a covS-mutant strain (McovS), and relevant complementary strains were constructed and investigated.  M35246 and McovS were significantly less encapsulated and exhibited poorer anti-phagocytic capacity compared to wild-type SEZ.  McovS was significantly more sensitive to β-lactams, aminoglycosides, macrolides, and lincosamides than wild-type SEZ.  M35246, McovS, and ΔPI exhibited an increase in median lethal dose (LD₅₀) in mice by 10⁵, 10⁵, and 5 times when compared to wild-type SEZ, respectively.  Neither M35246 nor McovS were isolated from mice 48 h after being challenged with approximately 2 000 times the LD₅₀ of wild-type SEZ.  Transcriptome analysis showed that 668 significantly differentially expressed genes existed between McovS and wild-type SEZ.  Numerous virulence factor-encoding genes and anabolic-related genes in McovS that were involved in anti-phagocytosis, capsule formation, pathogenicity, and antibiotic resistance were downregulated significantly relative to the wild-type strain.  This study revealed that the CovS plays a vital role in the establishment of SEZ virulence

Globally, white clover (Trifolium repens L.) is commonly infected by plant viruses.  It is grown at gardens, roadsides, and public areas as ornamental plants in northern China.  Some leaves present disease symptoms that are similar to those of virus infection.  However, to our knowledge, no records are available from China regarding white clover (Trifolium repens L.) virus co-infection.  To determine the viral species that infect white clover in China, plant samples with virus disease symptoms were collected and virion morphology and ultrastructure morphology of co-infected plants were observed by electron microscopy; viruses were detected by enzyme linked immunosorbent assay (ELISA) and reverse transcription PCR (RT-PCR).  Virus co-infection was studied by double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) and real-time fluorescence quantitative PCR (RT-qPCR) after rub-inoculation of virus-free white clover planted in a growth chamber (25°C) with a photoperiod of 16 h, using single or several purified virions.  Results showed that there were six types of symptoms, including those of shrinking mosaic, shrinking and macular mosaic, severe mottle mosaic, yellow macular mosaic, shrinkage chlorisis, and ring plaque and ring stria.  The incidence rates for each symptom were 20.93, 1.48, 16.85, 59.07, 1.30, and 0.37%, respectively, based on the field investigation.  Two types of viral pathogens were identified as Alfalfa mosaic virus (AMV) and White clover mosaic virus (WCMV).  In mesophyll cells, virus particles with bacilliform virions formed aggregates and linear virions were bundle shaped.  The detection rate of AMV was 100% in white clover samples by DAS-ELISA and RT-PCR detection, whereas that of WCMV was 83.33%.  The co-infection rate was 83.33%.  The relative contents of AMV and WCMV were significantly increased by 5.897- and 3.515-fold upon co-infection, when compared to that with single virus infection.  We observed larger starch particles and fewer or collapsed chloroplast grana in co-infected plants; in addition, vacuoles were twisted and smaller, compared to those of healthy plants.  To our knowledge, this is the first report of co-infection by AMV and WCMV in white clover, which has caused severe mosaicism and ultrastructure lesions in co-infected plants in China.

To reveal photosynthetic characteristics and biomass yield is important for evaluating introduced species adaptation to local environments.  A field experiment was conducted over three consecutive years (2011–2013) to evaluate photosynthetic characteristics, soil water content, aboveground biomass accumulation, and water use efficiency (WUE) in switchgrass (Panicum virgatum L.) populations exposed to three row spacing (20, 40 and 60 cm) treatments in two growth months (June and August) on the semiarid Loess Plateau of China.  Results indicated that net photosynthetic rate (P_n), transpiration rate (T_r), instantaneous water use efficiency (WUE_i) and plant height of switchgrass showed an increased trend, but aboveground biomass production and WUE showed an decreased trend with enlarged row spacings over the three years.  The maximum daily mean P_n values (17.9, 18.4 and 19.7 µmol CO₂ m^–2 s^–1) were observed in 2011, and the highest aboveground biomass production (67 771.8, 6 976.8 and 6 609.2 kg ha^–1) were recorded in 2012 for 20, 40 and 60 cm, respectively.  A close correlation between tiller numbers and aboveground biomass production (r=0.907) was observed.  P_n was positively and significantly correlated with biomass per tiller, but it showed a negative correlation with aboveground biomass production.  Our results confirm that wide row spacing is beneficial for single plant development, while narrow row spacing favors biomass production and water use of switchgrass in the region.  It also implies that single leaf growth and performance could explain the switchgrass community density differences, while fails to account for the aboveground biomass production.

A large portion of the Loess Plateau of China is characterized as “marginal” with serious land degradation and desertification problems.  Consequently, two policies, Grain for Green and Western Development Action were established by the Chinese government in response to the demand for ecological protection and economic development in the Loess Plateau.  These policies are designed to increase forest cover, expand farmlands, and enhance soil and water conservation, while creating sustainable vegetation restoration.  Perennial grasses have gained attention as bioenergy feedstocks due to their high biomass yields, low inputs, and greater ecosystem services compared to annual crops.  Moreover, perennial grasses limit nutrient runoff and reduce greenhouse gas emissions and soil losses while sequestering carbon.  Additionally, perennial grasses can generate economic returns for local farmers through producing bioenergy feedstock or forage on marginal lands.  Here, we suggest a United States model energy crop, switchgrass (Panicum virgatum L.) as a model crop to minimize land degradation and desertification and to generate biomass for energy on the Loess Plateau.

Two pot experiments were conducted to study the effects of root pruning at the stem elongation stage on non-hydraulic root-sourced signals (nHRS), drought tolerance and water use efficiency of winter wheat (Triticum aestivum). The root pruning significantly reduced the root weight of wheat, but had no effect on root/shoot ratio at the two tested stages. At booting stage, specific root respiration of root pruned plants was significantly higher than those with intact roots (1.06 and 0.94 mmol g-1 s-1, respectively). The soil water content (SWC) at which nHRS for root pruned plants appeared was higher and terminated lower than for intact root plants, the threshold range of nHRS was markedly greater for root pruned plants (61.1-44.6% field water capacity) than for intact root plants (57.9-46.1% field water capacity). At flowering stage, while there was no significant difference in specific root respiration. The SWCs at which nHRS appeared and terminated were both higher for root pruned plants than for intact root plants. The values of chlorophyll fluorescence parameters, i.e., the effective photosystem II quantum yield ( PS II), the maximum photochemical efficiency of PS II (Fv/Fm), coefficient of photochemical quenching (qP), and coefficient of non-photochemical quenching (NPQ), in root pruned plants were significantly higher than in intact root plants, 7 d after withholding of water. Root pruned plants had significantly higher water use efficiency (WUE) than intact root plants in well-watered and medium drought soil, but not in severe drought condition. In addition, root pruning had no significant effect on grain yield in well-watered and medium drought soil, but significantly decreased grain yield in severe drought condition. In conclusion, the current study showed that root pruning significantly altered nHRS sensitivity and improved WUE of winter wheat in well-watered and medium drought soil, but lowered drought tolerance of winter wheat in severe drought soil. This suggests a possible direction of droughtresistance breeding and potential agricultural measure to improve WUE of winter wheat under semiarid conditions.