Distribution Dynamics and Roles of Starch in Non-photosynthetic Vegetative Organs of Santalum album Linn., a Hemiparasitic Tree.

Allocation dynamics of stored starch plays essential roles in the development and growth of trees. Previous studies focused on the dynamics and the characteristics of starch in autotrophic trees. However, although starch granules have been detected in the organs or tissues of some parasitic plants, studies on the allocation dynamics and roles of storage starch in them are limited. Therefore, we determined and estimated the allocation dynamics and roles of starch in Santalum album Linn., a hemiparasitic tree, using morphological and physiological methods. Our findings showed abundant starch in the stem and root of S. album at the early seedling stage. Although S. album seedlings attached to the host showed no significant changes in starch levels throughout the experiment, unattached and host-removed seedlings exhibited a gradual decrease in the starch content over time. When the starch content of unattached seedlings was less than 1%, they started to die. Starch accumulated to high levels in developing and active haustoria; however, starch levels were low in the inactive haustoria. The present study suggests that starch may provide energy to seedlings that have no host, allowing them to survive during the unattached phase, thus increasing their chance to attach to host roots by extending their survival duration. In addition, we speculate that storage starch is potentially involved in the development of haustoria and in the physiological processes of S. album related to the absorption and transportation of water and nutrients from its host.

[Effects of weeding and fertilization on soil nitrogen mineralization and leaching in the mixed forest of Dalbergia odorifera and Santalum album]. / é“²è‰å’Œæ–½è‚¥å¯¹é™é¦™é»„æª€ä¸Žå°åº¦æª€é¦™æ··äº¤æž—åœŸå£¤æ°®ç´ çŸ¿åŒ–æ·‹æº¶çš„å½±å“.

The mixed plantation of precious tree species Dalbergia odorifera and Santalum album is an important model for the development of plantations in South China. Based on an experiment with four treatments, i.e., CK (without any treatment), weeding, fertilization, weeding+fertilization, we investigated the effects of weeding and fertilization on soil net mineralization rate, net nitrification rate, net ammonification rate, and nitrogen leaching rate. Among the four treatments, the maximum net nitrogen mineralization rate in the 0-10 cm soil layer was 18.92 and 18.13 mg·kg-1·month-1 in spring and autumn, respectively; the maximum nitrification rate was 20.35 and 18.85 mg·kg-1·month-1in spring and autumn, respectively; the maximum ammonium mineralization rate was 0.22 and 0.26 mg·kg-1·month-1 in summer and winter, respectively; the maximum nitrogen leaching was 15.98 mg·kg-1·month-1 in autumn and 86.69 mg·kg-1·year-1 in the whole year. The treatments of weeding, fertilization, weeding+fertilization reduced net mineralization rate and net nitrification rate. The annual nitrogen mineralization decreased by 26.2%, 16.1% and 6.3%, respectively, and the annual nitrogen nitrification decreased by 17.1%, 16.6%, and 1.4%, respectively. Moreover, the treatments of weeding, fertilization, weeding+fertilization inhibited soil ammonium accumulation and reduced annual nitrogen leaching by 25.2%, 8.6%, and 6.1%, respectively. Compared with weeding, fertilization and weeding+fertilization, seasonal factors had more significant effects on soil nitrogen mineralization and leaching. Weeding, fertilization and weeding+fertilization decreased soil nitrogen nitrification and ammonification to a certain extent, reduced soil nitrogen mineralization and leaching loss, which contribute to the preservation of soil fertility and nitrogen accumulation.

Genetic Diversity and Population Structure Analysis of DalbergiaOdorifera Germplasm and Development of a Core Collection Using Microsatellite Markers.

Dalbergia odorifera T. Chen (Fabaceae) is a woody tree species indigenous to Hainan Island in China. Due to its high medicinal and commercial value, this tree species has been planted over 3500 ha² in southern China. There is an urgent need for improvement of the D. odorifera germplasm, however, limited information on germplasm collection, conservation, and assessment of genetic resources is available. Therefore, we have built a database of 251 individuals collected across the whole of southern China, which included 42 wild trees and 210 cultivated trees, with the following objectives. (1) Evaluate genetic diversity and population structure of the database using 19 microsatellite markers and (2) develop a core collection for improvement and breeding programs. Totally, the 19 microsatellite markers harbored 77 alleles across the database with the polymorphic information content (PIC) ranging from 0.03 to 0.66. Medium genetic diversity level was inferred by Nei's gene diversity (0.38), Shannon's information index (0.65), and observed (0.33) and expected heterozygosity (0.38). Structure analysis showed that four was the optimum cluster size using the model-based Bayesian procedure, and the 251 D. odorifera individuals were grouped into five populations including four pure ones (RP1-4) and one mixed one (MIX) based on their maximum membership coefficients. Among these populations, the expected heterozygosity varied from 0.30 (RP3) to 0.38 (RP4). Analysis of molecular variance (AMOVA) showed 11% genetic variation existed among populations, and moderate population differentiation was inferred by the matrix of pairwise Fst (genetic differentiation among populations), which was in the range of 0.031 to 0.095. Moreover, a core collection of 31 D. odorifera individuals including six wild and 25 cultivated trees was developed, which was only 12.4% of the database but conserved the whole genetic diversity. The results of this study provided additional insight into the genetic structure of the large D. odorifera germplasm, and the core collection will be useful for the efficient and sustainable utilization of genetic resources, as well as efficient improvement in breeding programs.

Characterization of the chloroplast genome of Cassia siamea Lain, a rosewood species from southeast China.

Cassia siamea is a rosewood species in Southwest China with high wood and medicinal value. To clarify genetic background of C. siamea, we sequenced chloroplast genome by Illumina Hiseq and PacBio Sequel. The whole genome was 148,437 bp in length, containing a large single copy region (77,723 bp), a small single copy region (18,462 bp) and a pair of inverted repeats regions (26,126 bp). The cp genome contained 102 genes (71 protein-coding genes, 27 tRNAs and 4 rRNAs). The phylogenetic analysis indicated that C. siamea is close to Senna tora within Cassiinae/Caesalpiniaceae. The complete chloroplast genome of C. siamea will provide useful resources for the development and utilization of this species and the phylogenetic study of Fabaceae.

A Potent Multi-functional Neuroprotective Derivative of Tetramethylpyrazine.

Neurodegenerative disorders are one of the leading causes of death among the elderly. Therapeutic approaches with a single target have proven unsuccessful in treating these diseases. Structural combination of multi-functional compounds may lead to a molecule with multiple properties. In this study, we designed and synthesized T-006, a novel analog derived from two multi-functional neuroprotective chemicals, tetramethylpyrazine and J147. The methoxyphenyl group of J147 was replaced by tetramethylpyrazine. Bioactivity evaluation showed that T-006 at very low concentrations had multi-functional neuroprotective effects including rescuing iodoacetic acid-induced neuronal loss, preventing oxidative stress-induced neurotoxicity and reducing glutamate-induced excitotoxicity in vitro. Most importantly, T-006 significantly ameliorated memory impairments in APP/PS1 transgenic mice. These multiple functions of a single molecule suggest that T-006 is a promising novel neuroprotective agent for treating various neurodegenerative disorders, including and in particular Alzheimer's disease.

A novel tetramethylpyrazine bis-nitrone (TN-2) protects against 6-hydroxyldopamine-induced neurotoxicity via modulation of the NF-κB and the PKCα/PI3-K/Akt pathways.

INTRODUCTION: The natural product tetramethylpyrazine (TMP) has a variety of biologic activities, including neuroprotection. Nitrones are powerful free radical scavengers. We have designed and synthesized a TMP derivative, TN-2, which is armed with two nitrone moieties. AIMS: In this study, we investigated the neuroprotective effect of TN-2 against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in vitro and in zebrafish. METHODS: PC12 cells, zebrafish and rats were exposed to 6-OHDA challenge. MTT assay, LDH release, Hoechst staining, DAF-FM staining, luciferase reporter construct transfection, and western blotting were applied to detect cell viability, apoptosis, intracellular nitric oxide (NO), NF-κB transcriptional activity and proteins expression. In zebrafish, whole-mount staining and real-time PCR were performed to quantify dopaminergic neurons and mRNA expression. Hematoxylin and eosin staining and immunohistochemistry for glial fibrillary acidic protein were used to detect the astrocyte activation in the unilateral 6-OHDA rat model. RESULTS: TN-2 but not TMP exhibited potent neuroprotective effect against 6-OHDA-induced apoptosis in PC12 cells. Moreover, TN-2 prevented dopaminergic neuron loss and suppressed mRNA expression of pro-inflammatory genes, including IL-1ß, TNF-α and COX-2, in 6-OHDA-treated zebrafish. TN-2 remarkably attenuated microglial/astrocyte activation in the unilateral 6-OHDA rat model. The mechanistic study demonstrated that TN-2 inhibited over-production of intracellular NO and protein expression of inducible nitric oxide synthase through down-regulating NF-κB activity. Additionally, the PKCα/PI3-K/Akt pathway was also involved in the neuroprotection of TN-2. CONCLUSION: These results suggest that TN-2 protected against 6-OHDA-induced neurotoxicity via modulating the NF-κB-medicated neuroinflammation and PKCα/PI3-K/Akt pathways.

Sunitinib produces neuroprotective effect via inhibiting nitric oxide overproduction.

BACKGROUND: Sunitinib is an inhibitor of the multiple receptor tyrosine kinases (RTKs) for cancer therapy. Some sunitinib analogues could prevent neuronal death induced by various neurotoxins. However, the neuroprotective effects of sunitinib have not been reported. METHODS: Cerebellar granule neurons (CGNs) and SH-SY5Y cells were exposed to low-potassium and MPP(+) challenges, respectively. MTT assay, FDA/PI staining, Hoechst staining, DAF-FM, colorimetric nitric oxide synthase (NOS) activity assay, and Western blotting were applied to detect cell viability, NO production, NOS activity, and neuronal NOS (nNOS) expression. Short hairpin RNA was used to decrease nNOS expression. In vitro NOS enzyme activity assay was used to determine the direct inhibition of nNOS by sunitinib. RESULTS: Sunitinib prevented low-potassium-induced neuronal apoptosis in CGNs and MPP(+) -induced neuronal death in SH-SY5Y cells. However, PTK787, another RTK inhibitor, failed to decrease neurotoxicity in the same models. Sunitinib reversed the increase in NO levels, NOS activity, and nNOS expression induced by low potassium or MPP(+) . Knockdown of nNOS expression partially abolished the neuroprotective effects of sunitinib. Moreover, sunitinib directly inhibited nNOS enzyme activity. CONCLUSIONS: Sunitinib exerts its neuroprotective effects by inhibiting NO overproduction, possibly via the inhibition of nNOS activity and the decrease in nNOS expression.

The environment, not space, dominantly structures the landscape patterns of the richness and composition of the tropical understory vegetation.

The mechanisms driving the spatial patterns of species richness and composition are essential to the understanding of biodiversity. Numerous studies separately identify the contributions of the environment (niche process) and space (neutral process) to the species richness or composition at different scales, but few studies have investigated the contributions of both types of processes in the two types of data at the landscape scale. In this study, we partitioned the spatial variations in all, exotic and native understory plant species richness and composition constrained by environmental variables and space in 134 plots that were spread across 10 counties in Hainan Island in southern China. The 134 plots included 70 rubber (Hevea brasiliensis) plantation plots, 50 eucalyptus (Eucalyptus urophylla) plantation plots, and 14 secondary forest plots. RDA based variation partitioning was run to assess the contribution of environment and space to species richness and composition. The results showed that the environmental variables alone explained a large proportion of the variations in both the species richness and composition of all, native, and exotic species. The RDA results indicated that overstory composition (forest type here) plays a leading role in determining species richness and composition patterns. The alpha and beta diversities of the secondary forest plots were markedly higher than that of the two plantations. In conclusion, niche differentiation processes are the principal mechanisms that shape the alpha and beta diversities of understory plant species in Hainan Island.

Substantial neuroprotection against K+ deprivation-induced apoptosis in primary cerebellar granule neurons by novel dimer bis(propyl)-cognitin via the activation of VEGFR-2 signaling pathway.

BACKGROUND: Neuronal loss via apoptosis in CNS is the fundamental mechanism underlying various neurodegenerative diseases. Compounds with antiapoptotic property might have therapeutic effects for these diseases. In this study, bis(propyl)-cognitin (B3C), a novel dimer that possesses anti-AChE and anti-N-methyl-d-aspartate receptor activities, was investigated for its neuroprotective effect on K(+) deprivation-induced apoptosis in cerebellar granule neurons (CGNs). METHODS: Cerebellar granule neurons were switched to K(+) deprived medium with or without B3C. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium assay, fluorescein diacetate (FDA)/propidium iodide (PI) staining, Hoechst staining, and DNA laddering assays were applied to detect cytotoxicity and apoptosis. Additionally, the expression of p-VEGFR-2, p-Akt, p-glycogen synthase kinase 3ß (GSK3ß), and p-extracellular signal-regulated kinase (ERK) was examined in CGNs. RESULTS: Switching CGNs to K(+) deprived medium resulted in remarkable apoptosis, which could be substantially blocked by B3C treatment (IC50 , 0.37 µM). Moreover, a rapid decrease in p-Tyr1054-VEGFR-2 was observed after the switch. B3C significantly reversed the inhibition of p-Tyr1054-VEGFR-2 as well as Akt and ERK pathways. VEGFR-2 inhibitor PTK787/ZK222584, as well as PI3-K inhibitor LY294002 and MEK inhibitor PD98059, each abolished the neuroprotective effect of B3C. CONCLUSIONS: Our results demonstrate that B3C blocks K(+) deprivation-induced apoptosis in CGNs through regulating VEGFR-2/Akt/GSK3ß and VEGFR-2/ERK signaling pathways, providing a molecular insight into the therapeutic potential of B3C for the treatment of neurodegenerative diseases.

Strong neutral spatial effects shape tree species distributions across life stages at multiple scales.

Traditionally, ecologists use lattice (regional summary) count data to simulate tree species distributions to explore species coexistence. However, no previous study has explicitly compared the difference between using lattice count and basal area data and analyzed species distributions at both individual species and community levels while simultaneously considering the combined scenarios of life stage and scale. In this study, we hypothesized that basal area data are more closely related to environmental variables than are count data because of strong environmental filtering effects. We also address the contribution of niche and the neutral (i.e., solely dependent on distance) factors to species distributions. Specifically, we separately modeled count data and basal area data while considering life stage and scale effects at the two levels with simultaneous autoregressive models and variation partitioning. A principal coordinates of neighbor matrix (PCNM) was used to model neutral spatial effects at the community level. The explained variations of species distribution data did not differ significantly between the two types of data at either the individual species level or the community level, indicating that the two types of data can be used nearly identically to model species distributions. Neutral spatial effects represented by spatial autoregressive parameters and the PCNM eigenfunctions drove species distributions on multiple scales, different life stages and individual species and community levels in this plot. We concluded that strong neutral spatial effects are the principal mechanisms underlying the species distributions and thus shape biodiversity spatial patterns.

[Growth effect of eucalyptus-acacia mixed plantation in South China].

Eucalyptus U6 and Acacia crassicarpa were mixed planted with different ratios and modes to investigate the growth parameters of the two tree species. In the 2-3 years old mixed plantation, the wind-throw of A. crassicarpa decreased markedly with increasing ratio of Eucalyptus U6, the decrement being 26.14% when the Eucalyptus U6/A. crassicarpa ratio was 3 : 1, but the survival rates of Eucalyptus U6 and A. crassicarpa had no significant difference under different planting modes. Mixed planting retarded the A. crassicarpa growth to some extent, with the DBH being 90% of that in pure A. crassicarpa stand. The mixed planting had little effects on the height growth of Eucalyptus U6, but promoted its DBH growth markedly, and the beneficial effect increased with increasing ratio of A. crassicarpa. In the 6 years old 1 : 1 Eucalyptus U6/A. crassicarpa plantation, the Eucalyptus U6 individuals with DBH > 15 cm occupied 32.1%; while in pure Eucalyptus U6 stand, they only accounted for 5.83%. Mixed planting with 2 : 1 Eucalyptus U6/A. crassicarpa could obtain a maximum total biomass of 198.8 m3 x hm(-2), which was 118.8% of the total biomass in pure Eucalyptus U6 stand, or 169.9% of that in pure A. crassicarpa stand. Mixture of Eucalyptus with Acacia would be a good choice to produce Eucalyptus trees with larger DBH.

[Soil macropore characteristics under typical vegetations in Liupan Mountains].

The radius and density of soil macropores under eight typical vegetations in Liupan Mountains of Northwest China were studied by using water breakthrough curves and Poiseuille equation. The results indicated that the radii of soil macropores ranged from 0.4 mm to 2.3 mm, and the weighted mean radii ranged from 0.57 mm to 1.21 mm, with a mean of 0.89 mm. The density of soil macropores ranged from 57 individuals per dm2 to 1 117 individuals per dm2, with a mean of 408 individuals per dm2. The macropores with radii bigger than 1.4 mm had a lower density, accounting for only 6.86% of the total. The area proportion of soil macropores ranged from 0.76% to 31.26%, with a mean of 10.82%. In study area, the density of soil macropores was higher in broadleaf forest than in coniferous forest, but basically the same in sub-alpine meadow and in broadleaf forest, as well as in shrubs and in coniferous forest. As for the area proportion of soil macropores, it was also higher in broadleaf forest than in coniferous forest, but basically the same in shrubs and in broadleaf forest soil, as well as in sub-alpine meadow and in coniferous forest.