Changing water use and adaptive strategies along rainfall gradients in Mediterranean lupins

• There is growing interest in harnessing the genetic and adaptive diversity of crop wild relatives to improve drought resilience of elite cultivars. Rainfall gradients exert strong selection pressure on both natural and agricultural ecosystems. Understanding plant responses to these facilitates crop improvement.
• Wild and domesticated narrow‐leafed lupin (NLL) collected along Mediterranean terminal drought stress gradients was evaluated under contrasting reproductive phase water supply in controlled field, glasshouse and cabinet studies. Plant phenology, growth and productivity, water use and stress responses were measured over time.
• There is an integrated suite of adaptive changes along rainfall gradients in NLL. Low rainfall ecotypes flower earlier, accumulate lower seed numbers, biomass and leaf area, and have larger root:shoot ratios than high rainfall ecotypes. Water‐use is lower and stress onset slower in low compared to high rainfall ecotypes. Water‐use rates and ecotypic differences in stress response (Ψleaf decline, leaf loss) are lower in NLL than yellow lupin (YL). To mitigate the effects of profligate water use, high rainfall YL ecotypes maintain higher leaf water content over declining leaf water potential than low rainfall ecotypes. There is no evidence for such specific adaptation in NLL.
• The data suggests that appropriate phenology is the key adaptive trait to rainfall gradients in NLL because of the flow‐on effects on biomass production, fitness, transpiration and stress onset, and the lack of physiological adaptations as in YL. Accordingly, it is essential to match phenology with target environment in order to minimize risk and maximize yield potential.

     

Phylogenetic diversity is a better predictor of wetland community resistance to Alternanthera philoxeroides invasion than species richness

• Highly biodiversity communities have been shown to better resist plant invasions through complementarity effects. Species richness (SR) is a widely used biodiversity metric but lacks explanatory power when there are only a few species. Communities with low SR can have a wide variety of phylogenetic diversities (PD), which might allow for a better prediction of invasibility.
• We assessed the effect of diversity reduction of a wetland community assemblage typical of the Beijing area on biotic resistance to invasion of the exotic weed Alternanthera philoxeroides and compared the reduction in SR and PD in predicting community invasibility.
• The eight studied resident species performed similarly when grown alone and when grown in eight‐species communities together with the invasive A. philoxeroides. Variation partitioning showed that PD contributed more to variation in both A. philoxeroides traits and community indicators than SR. All A. philoxeroides traits and community indicators, except for evenness index, showed a linear relationship with PD. However, only stem length of A. philoxeroides differed between the one‐ and two‐species treatments, and the diversity index of the communities differed between the one‐ and two‐species treatments and between the one‐ and four‐species treatments.
• Our results showed that in natural or semi‐natural wetlands with relatively low SR, PD may be a better predictor of invasibility than SR. When designing management strategies for mitigating A. philoxeroides invasion, deliberately raising PD is expected to be more efficient than simply increasing species number.

     

Temperature thresholds for germination in 20 short‐range endemic plant species from a Greenstone Belt in southern Western Australia

• The study of climate‐driven effects on seed traits such as germination has gained momentum over the past decade as the impact of global warming becomes more apparent on the health and survival of plant diversity.
• Seed response to warming was evaluated in a suite of short‐range endemic species from the biodiverse Greenstone Belt of southern Western Australia. The temperature dimensions for germination in 20 woody perennials were identified using small unreplicated samples over 6 weeks on a temperature gradient plate (constant and fluctuating temperatures between 5 and 40 °C). These data were subsequently modelled against current and forecast (2070) mean monthly minimum and maximum temperatures to illustrate seasonal changes to germination timing and final percentage germination.
• All but one species attained full germination in at least one cell on the gradient plate. Modelling of the data suggested only minimal changes to percentage germination despite a forecast rise in diurnal temperatures over the next 50 years. Nine species were predicted to experience declines of between <1% and 7%, whilst 11 species were predicted to increase their germination by <1% to 3%. Overall, the speed of germination is predicted to increase but the timing of germination for most species shifts seasonally (both advances and delays) as a result of changing diurnal temperatures.
• The capacity of this suite of species to cope with warmer temperatures during a critical early life stage shows a degree of adaptation to heterogeneous environments. Predicting the effects of global change on terrestrial plant communities is crucial to managing and conserving plant diversity.

     

Origin of the cultivated passion fruit Passiflora edulis f. flavicarpa and genomic relationships among species of the subgenera Decaloba and Passiflora

• Passiflora edulis f. flavicarpa is the most economically important species in the genus Passiflora. However, the origin of this yellow form of passion fruit remains unclear, being suggested as a hybrid (P. edulis f. edulis × P. ligularis) or wild mutant.
• Here, the origin and genomic relationships of P. edulis f. flavicarpa with some related species in the genus Passiflora (subgenera Decaloba and Passiflora) were investigated using genomic in situ hybridization (GISH). Genomic DNA of 18 species was used as probe, which was hybridized onto chromosomes of P. edulis f. flavicarpa.
• Of all genomic DNA probes tested, none allowed us to identify a specific chromosome set in P. edulis f. flavicarpa. Conversely, probes from the subgenus Passiflora, P. edulis f. edulis, P. alata, P. cincinnata, P. coccinea, P. nitida and P. vitifolia, produced intense and uniform hybridizations on all chromosomes of P. edulis f. flavicarpa. Moreover, probes from P. ligularis, P. foetida and P. sublanceolata produced more intense hybridizations in the terminal region of four chromosomes, corresponding to the DNAr 45S locus, and also dispersed, less intense, hybridization across all chromosomes. Probes from the subgenus Decaloba, P. biflora, P. capsularis, P. cervii, P. coriacea, P. micropetala, P. morifolia, P. rubra and P. suberosa, produced hybridizations restricted to the DNAr 45S sites.
• The hybrid origin of P. edulis f. flavicarpa could not be supported based on the GISH results, and it is suggested that this species is conspecific with P. edulis f. edulis, because the probe with DNA of this form hybridized strongly throughout the target genome. The other putative parent species, P. ligularis, showed only a distant relationship with the target genome. The results also suggest that species of the subgenus Passiflora share many repetitive sequences and that the relationship between subgenera Decaloba and Passiflora is very distant.

     

Evaluation of Corrosion Resistance and Characterization of Ni-Cr Coated Structure Using Plasma Spray Coating for Marine Hulls

Plasmonics - Corrosion is a natural process which gradually destructs the materials with their environment by chemical or electrochemical means. Mechanized boat hull structures used in fishing were...     

Sea Anemones as Potential Source for Bioactive Metabolites

International Journal of Peptide Research and Therapeutics - Marine organisms are novel sources for biologically active compounds which are potentially valuable materials in biomedical research. In...     

β2-Microglobulin Amyloid Fibrils Are Nanoparticles That Disrupt Lysosomal Membrane Protein Trafficking and Inhibit Protein Degradation by Lysosomes

Fragmentation of amyloid fibrils produces fibrils that are reduced in length but have an otherwise unchanged molecular architecture. The resultant nanoscale fibril particles inhibit the cellular reduction of the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), a substrate commonly used to measure cell viability, to a greater extent than unfragmented fibrils. Here we show that the internalization of β₂-microglobulin (β₂m) amyloid fibrils is dependent on fibril length, with fragmented fibrils being more efficiently internalized by cells. Correspondingly, inhibiting the internalization of fragmented β₂m fibrils rescued cellular MTT reduction. Incubation of cells with fragmented β₂m fibrils did not, however, cause cell death. Instead, fragmented β₂m fibrils accumulate in lysosomes, alter the trafficking of lysosomal membrane proteins, and inhibit the degradation of a model protein substrate by lysosomes. These findings suggest that nanoscale fibrils formed early during amyloid assembly reactions or by the fragmentation of longer fibrils could play a role in amyloid disease by disrupting protein degradation by lysosomes and trafficking in the endolysosomal pathway.     

TMTC1 and TMTC2 Are Novel Endoplasmic Reticulum Tetratricopeptide Repeat-containing Adapter Proteins Involved in Calcium Homeostasis

The endoplasmic reticulum (ER) is organized in part by adapter proteins that nucleate the formation of large protein complexes. Tetratricopeptide repeats (TPR) are well studied protein structural motifs that support intermolecular protein-protein interactions. TMTC1 and TMTC2 were identified by an in silico search as TPR-containing proteins possessing N-terminal ER targeting signal sequences and multiple hydrophobic segments, suggestive of polytopic membrane proteins that are targeted to the secretory pathway. A variety of cell biological and biochemical assays was employed to demonstrate that TMTC1 and TMTC2 are both ER resident integral membrane proteins with multiple clusters of TPR domains oriented within the ER lumen. Proteomic analysis followed by co-immunoprecipitation verification found that both proteins associated with the ER calcium uptake pump SERCA2B, and TMTC2 also bound to the carbohydrate-binding chaperone calnexin. Live cell calcium measurements revealed that overexpression of either TMTC1 or TMTC2 caused a reduction of calcium released from the ER following stimulation, whereas the knockdown of TMTC1 or TMTC2 increased the stimulated calcium released. Together, these results implicate TMTC1 and TMTC2 as ER proteins involved in ER calcium homeostasis.     

Flavone-resistant Leishmania donovani Overexpresses LdMRP2 Transporter in the Parasite and Activates Host MRP2 on Macrophages to Circumvent the Flavone-mediated Cell Death

In parasites, ATP-binding cassette (ABC) transporters represent an important family of proteins related to drug resistance and other biological activities. Resistance of leishmanial parasites to therapeutic drugs continues to escalate in developing countries, and in many instances, it is due to overexpressed ABC efflux pumps. Progressively adapted baicalein (BLN)-resistant parasites (pB²⁵R) show overexpression of a novel ABC transporter, which was classified as ABCC2 or Leishmania donovani multidrug resistance protein 2 (LdMRP2). The protein is primarily localized in the flagellar pocket region and in internal vesicles. Overexpressed LdABCC2 confers substantial BLN resistance to the parasites by rapid drug efflux. The BLN-resistant promastigotes when transformed into amastigotes in macrophage cells cannot be cured by treatment of macrophages with BLN. Amastigote resistance is concomitant with the overexpression of macrophage MRP2 transporter. Reporter analysis and site-directed mutagenesis assays demonstrated that antioxidant response element 1 is activated upon infection. The expression of this phase II detoxifying gene is regulated by NFE2-related factor 2 (Nrf2)-mediated antioxidant response element activation. In view of the fact that the signaling pathway of phosphoinositol 3-kinase controls microfilament rearrangement and translocation of actin-associated proteins, the current study correlates with the intricate pathway of phosphoinositol 3-kinase-mediated nuclear translocation of Nrf2, which activates MRP2 expression in macrophages upon infection by the parasites. In contrast, phalloidin, an agent that prevents depolymerization of actin filaments, inhibits Nrf2 translocation and Mrp2 gene activation by pB²⁵R infection. Taken together, these results provide insight into the mechanisms by which resistant clinical isolates of L. donovani induce intracellular events relevant to drug resistance.