Drought- and frost-induced accumulation of soluble carbohydrates during accelerated senescence in <Emphasis Type="Italic">Quercus pubescens</Emphasis>

Key message

Different environmental conditions affect tree senescence by different patterns of carbohydrate concentrations and have specific impact on the dissection of the photosynthetic apparatus.

Abstract

A proactive cultivation of Mediterranean broadleaf species, including oaks, has been suggested to fill possible temporal and spatial gaps in forestry created by Climate Change in Central Europe in the future. Climate can affect trees in several different ways, e.g., by modulating the course of leaf senescence. Senescence-associated processes, like regulation of carbohydrates and changes in chlorophyll fluorescence under drought stress conditions were studied with leaf tissue of drought-tolerant downy oak (Quercus pubescens). Two months of consistent drought stress in a frost-free greenhouse led to significantly earlier senescence and significant increased amounts of soluble sugars in the leaves of the drought-stressed group in comparison to a well-watered control group. Similar sugar accumulation was observed in trees outdoors, after exposure to frost. In contrast to monocarpic plants the accumulation of free sugars is neither triggering leaf senescence, nor is it a side effect of age-depending changes in Q. pubescens. Instead, sugar accumulation is induced by abiotical factors, like drought and frost. Furthermore, we suggest that the senescence process in the absence of drought stress or frost depends on the source status of the leaf, which, in term, is a function of light (through photosynthesis) and night temperature (through respiration). Contents of the storage metabolite starch decreased during late summer in all three groups. Drought-stressed plants showed a decline of the connectivity of photosystem II antenna, reflected as the L-band in the chlorophyll fluorescence induction curves, and stronger correlations between the declines in the capacity of photosynthetic dark reactions and electron transport-associated chlorophyll fluorescence parameters. We conclude that the disassembly of single parts of the photosynthetic apparatus during leaf senescence is a uniform process, but the onset of this process depends on abiotical environmental factors.

     

Clinical utility of plasma miR‐371a‐3p in germ cell tumors

Germ cell tumours predominantly of the testis ((T)GCTs) are remarkably chemotherapy sensitive. However, a small proportion of patients fail to be cured with cisplatin‐based combination chemotherapy. miR‐371a‐3p is a new liquid biopsy biomarker for (T)GCTs. The aim of this study was to evaluate clinical utility of plasma miR‐371a‐3p level in patients starting systemic chemotherapy. Patients were included before the first cycle (N = 180) and second cycle (N = 101) of systemic first line chemotherapy, treated between July 2010 and May 2017. Plasma miR‐371a‐3p levels were measured with the ampTSmiR test and compared to disease characteristics and outcome. Pretreatment plasma miR‐371a‐3p levels were increased in 51.7% of cases and associated with number of metastatic sites, presence of lung, retroperitoneal, and mediastinal lymph node metastases, S – stage, IGCCCG risk group, and response to therapy. Patients with a negative pretreatment plasma level had better progression‐free survival (PFS) and overall survival (OS) compared to patients being positive for miR‐371a‐3p (hazard ratio [HR] = 0.26, 95% confidence interval [CI] 0.09‐0.71, P = 0.02 for PFS and HR = 0.21, 95% CI 0.07‐0.67, P = 0.03 for OS, respectively). Patients negative for miR‐371a‐3p in both samples had a superior PFS (HR = 0.10, 95% CI 0.01‐21.49, P = 0.02) and OS (HR = 0.08, 95% CI 0.01‐27.81, P = 0.008) compared to patients with miR‐371a‐3p positive in both samples (multivariate analyses were non‐significant). In total 68% of the patients were S0. This study demonstrates clinical value of plasma miR‐371a‐3p level in chemotherapy naïve (T)GCT patients starting first line of chemotherapy to predict prognosis.     

Chemical and Morphological Inter‐ and Intrapopulation Variability in Natural Populations of Gentiana pneumonanthe L.

Inter‐ and intrapopulation variability in six natural populations of the rare species Gentiana pneumonanthe was examined based on morphological and chemical data. Population size and linear morphometric parameters differed significantly among populations, but without a clear connection to habitat conditions, i. e. water supply and light availability. Leaf shape varied from ovate to lanceolate in all populations, and one population was distinctive in having the largest number of leaves of transitional shape. HPLC analyses of six secondary metabolites were performed separately for belowground parts, and aboveground vegetative and reproductive parts of individual plants (6 populations ×7 individuals ×3 plant parts, n=126) in order to examine differences at the population and individual levels. Three secoiridoids (swertiamarin (SWM), sweroside (SWZ), and gentiopicrin (GP)), one xanthone (mangiferin (MGF)), and two flavones (isoorientin (IO) and isovitexin (IV)) were detected and quantified in the analyzed samples: sweroside dominated in the aboveground reproductive part, mangiferin in the aboveground vegetative part, and gentiopicrin in the belowground part. At the population level, differences in contents of the analyzed chemicals among populations were significant only for a few metabolites. At the individual level, a pronounced organ‐dependent distribution of secondary metabolites was revealed. The results of this study contribute to a better understanding of natural variability within populations of the rare and threatened G. pneumonanthe, and provide data on the contents and within‐plant distribution of secondary metabolites, which are important as pharmacologically active compounds and may be useful for further biotechnological procedures regarding this species.     

Characterization of the mitochondrial genome of the MAX1 type of cytoplasmic male-sterile sunflower

Background

More than 70 cytoplasmic male sterility (CMS) types have been identified in Helianthus, but only for less than half of them, research of mitochondrial organization has been conducted. Moreover, complete mitochondrion sequences have only been published for two CMS sources – PET1 and PET2. It has been demonstrated that other sunflower CMS sources like MAX1, significantly differ from the PET1 and PET2 types. However, possible molecular causes for the CMS induction by MAX1 have not yet been proposed. In the present study, we have investigated structural changes in the mitochondrial genome of HA89 (MAX1) CMS sunflower line in comparison to the fertile mitochondrial genome.

Results

Eight significant major reorganization events have been determined in HA89 (MAX1) mtDNA: one 110 kb inverted region, four deletions of 439 bp, 978 bp, 3183 bp and 14,296 bp, respectively, and three insertions of 1999 bp, 5272 bp and 6583 bp. The rearrangements have led to functional changes in the mitochondrial genome of HA89 (MAX1) resulting in the complete elimination of orf777 and the appearance of new ORFs - orf306, orf480, orf645 and orf1287. Aligning the mtDNA of the CMS sources PET1 and PET2 with MAX1 we found some common reorganization features in their mitochondrial genome sequences.

Conclusion

The new open reading frame orf1287, representing a chimeric atp6 gene, may play a key role in MAX1 CMS phenotype formation in sunflower, while the contribution of other mitochondrial reorganizations seems to appear negligible for the CMS development.

     

Biodiversity,dynamics, and impact of chakras on the Ecuadorian Amazon

Aims Deforestation and biodiversity loss are two alarming, closely related problems, and the main factors triggering changes in land use. Indigenous agricultural practices in the western Amazon Basin are known as chakras, and their structure and dynamics are seemingly optimal for forest management. However, the variability in tree species and the degree of forest recovery after abandonment is poorly documented in this agroforestry system (AFS). The goals of this study were: (i) to investigate whether the different AFSs (chakras) preserve similar levels of forest diversity, (ii) to determine the effect of transformation of mature forests (MF) to chakras, in particular, forest alpha and beta diversity levels, and (iii) to investigate whether native tree species recovery leads to the original forest structure following chakra abandonment.     

Analysis of a new flavodiiron core structural arrangement in Flv1-ΔFlR protein from Synechocystis sp. PCC6803

Flavodiiron proteins (FDPs) play key roles in biological response mechanisms against oxygen and/or nitric oxide; in particular they are present in oxygenic phototrophs (including cyanobacteria and gymnosperms). Two conserved domains define the core of this family of proteins: a N-terminal metallo-β-lactamase-like domain followed by a C-terminal flavodoxin-like one, containing the catalytic diiron centre and a FMN cofactor, respectively. Members of the FDP family may present extra modules in the C-terminus, and were classified into several classes according to their distribution and composition. The cyanobacterium Synechocystis sp. PCC6803 contains four Class C FDPs (Flv1-4) that include at the C-terminus an additional NAD(P)H:flavin oxidoreductase (FlR) domain. Two of them (Flv3 and Flv4) have the canonical diiron ligands (Class C, Type 1), while the other two (Flv1 and Flv2) present different residues in that region (Class C, Type 2). Most phototrophs, either Bacterial or Eukaryal, contain at least two FDP genes, each encoding for one of those two types. Crystals of the Flv1 two core domains (Flv1-ΔFlR), without the C-terminal NAD(P)H:flavin oxidoreductase extension, were obtained and the structure was determined. Its pseudo diiron site contains non-canonical basic and neutral residues, and showed anion moieties, instead. The presented structure revealed for the first time the structure of the two-domain core of a Class C-Type 2 FDP.     

A hybrid model for erythrocyte membrane: a single unit of protein network coupled with lipid bilayer

To investigate the nanomechanics of the erythrocyte membrane we developed a hybrid model that couples the actin-spectrin network to the lipid bilayer. This model features a Fourier space Brownian dynamics model of the bilayer, a Brownian dynamics model of the actin protofilament, and a modified wormlike-chain model of the spectrin (including a cable-dynamics model to predict the oscillation in tension). This model enables us to predict the nanomechanics of single or multiple units of the protein network, the lipid bilayer, and the effect of their interactions. The present work is focused on the attitude of the actin protofilament at the equilibrium states coupled with the elevations of the lipid bilayer through their primary linkage at the suspension complex in deformations. Two different actin-spectrin junctions are considered at the junctional complex. With a point-attachment junction, large pitch angles and bifurcation of yaw angles are predicted. Thermal fluctuations at bifurcation may lead to mode-switching, which may affect the network and the physiological performance of the membrane. In contrast, with a wrap-around junction, pitch angles remain small, and the occurrence of bifurcation is greatly reduced. These simulations suggest the importance of three-dimensional molecular junctions and the lipid bilayer/protein network coupling on cell membrane mechanics.