Genetic variation of stomatal traits and carbon isotope discrimination in two hybrid poplar families (Populus deltoides 'S9-2' x P. nigra 'Ghoy' and P. deltoides 'S9-2' x P. trichocarpa 'V24')

Background and Aims

Stomata play an important role in both the CO₂ assimilation and water relations of trees. Therefore, stomatal traits have been suggested as criteria for selection of clones or genotypes which are more productive and have larger water-use efficiency (WUE) than others. However, the relationships between plant growth, WUE and stomatal traits are still unclear depending on plant material (genus, species, families, genotypes) and, more precisely, on the strength of the relationships between the plants. In this study, the correlations between these three traits categories, i.e. plant growth, WUE and stomatal traits, were compared in two related poplar families.

Methods

Stomatal traits (stomatal density, length and ratio adaxial : abaxial stomatal densities) of a selection of F₁ genotypes and the parents of two hybrid poplar families Populus deltoides ‘S9-2’ × P. nigra ‘Ghoy’ (D × N family, 50 F₁) and P. deltoides ‘S9-2’ × P. trichocarpa ‘V24’ (D × T family, 50 F₁) were measured, together with stem height and circumference. Carbon isotope discrimination (Δ) was determined and used as an indicator of leaf-level intrinsic WUE.

Key Results

Leaves of hybrids and parents were amphistomatous, except for the P. trichocarpa parent. Both families displayed high values of heritability for stomatal traits and Δ. In the progeny, the relationship between stem circumference and Δ was weak for the D × N family, while abaxial and total stomatal density were positively associated with stem dimensions for the D × T family only.

Conclusions

Genetic variation in stomatal traits and Δ was large within as well as between the different poplar species and their hybrids, but there were no direct relationships between stomatal traits and plant growth or Δ. As already noticed in various poplar hybrids, the absence of, or the weak, relationship between Δ and plant growth allows the possibility of selecting poplar genotypes combining high productivity and high WUE. In this study, stomatal traits are of limited value as criteria for selection of genotypes with good growth and large WUE.Key words: Adaxial and abaxial stomatal density, stomatal length, heritability, water-use efficiency (WUE), F₁ hybrids, breeding, Populus deltoides, Populus nigra, Populus trichocarpa     

Role of endogenous interleukin-12 (IL-12) in induced and spontaneous relapses of experimental autoimmune encephalomyelitis in mice.

Actively induced, chronic relapsing experimental autoimmune encephalomyelitis (CREAE) was studied in SJL/J and in Biozzi ABH mice. In Biozzi ABH mice, relapses occurred spontaneously with high frequency. In SJL/J mice, spontaneous relapses occurred infrequently; however they could be induced reproducibly by reimmunization. In both models, moderately increased levels of serum IL-12(p40) were consistently found shortly before primary attacks, but irregularly at later times. Injections of anti-IL-12 antibody inhibited disease development in both SJL/J and in Biozzi ABH mice. The time window during which treatment needed to be initiated in order to be effective, ranged from before induction until shortly before the symptoms of primary attacks emerged. Such treatment inhibited not only the first attack but also the spontaneous or induced relapses. Most significantly, anti-IL-12 antibody given during remission of primary disease inhibited actively re-induced relapses in SJL/J, but not spontaneous relapses in Biozzi ABH mice. These results indicate that endogenous IL-12 favours EAE development by crucially affecting the active induction process, but that a second burst of IL-12 production may not be necessary for triggering spontaneous relapses.     

Evaluation of a novel subtilisin inhibitor gene and mutant derivatives for the expression and secretion of mouse tumor necrosis factor alpha by Streptomyces lividans.

In order to evaluate the expression and secretion signals of the highly secreted subtilisin inhibitor of Streptomyces venezuelae CBS762.70 (VSI) for the production of heterologous proteins by Streptomyces lividans, mouse tumor necrosis factor alpha (mTNF) was chosen as a model protein. The mTNF cDNA was fused to the vsi signal sequence. The analysis of secretion by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and biological activity measurements revealed an efficient translocation of mTNF. Up to 300 mg of secreted biologically active mTNF per liter could be obtained in shaken-flask cultures. By analyzing the effects of mutations in the N region of the VSI signal peptide on secretion, we found that decreasing the +3 charge of the wild-type protein to +2 resulted in a 3- to 10-fold increase in secretion.     

Involvement of claudin-7 in HIV infection of CD4(-) cells

Background

The antibacterial activity of host defense peptides (HDP) is largely mediated by permeabilization of bacterial membranes. The lipid membrane of enveloped viruses might also be a target of antimicrobial peptides. Therefore, we screened a panel of naturally occurring HDPs representing different classes for inhibition of early, Env-independent steps in the HIV replication cycle. A lentiviral vector-based screening assay was used to determine the inhibitory effect of HDPs on early steps in the replication cycle and on cell metabolism.

Results

Human LL37 and porcine Protegrin-1 specifically reduced lentiviral vector infectivity, whereas the reduction of luciferase activities observed at high concentrations of the other HDPs is primarily due to modulation of cellular activity and/or cytotoxicity rather than antiviral activity. A retroviral vector was inhibited by LL37 and Protegrin-1 to similar extent, while no specific inhibition of adenoviral vector mediated gene transfer was observed. Specific inhibitory effects of Protegrin-1 were confirmed for wild type HIV-1.

Conclusion

Although Protegrin-1 apparently inhibits an early step in the HIV-replication cycle, cytotoxic effects might limit its use as an antiviral agent unless the specificity for the virus can be improved.     

Sperm transfer, sperm storage, and sperm digestion in the hermaphroditic land snail Succinea putris (Gastropoda, Pulmonata)

Abstract. Many hermaphroditic species are promiscuous, have a sperm digesting organ and an allosperm storage organ (i.e., spermatheca) with multiple compartments (i.e., spermathecal tubules) providing opportunities for sperm competition. The relative paternity of a sperm donor drives the evolution of mating behaviors that allow manipulation of the sperm receiver's reproductive behavior or physiology. We studied the relationship between sperm transfer, sperm storage, sperm digestion, and copulation duration in the hermaphroditic land snail Succinea putris , in which an active individual mates on top of a passive individual. Specifically, we examined (i) whether the entire copulation duration was required to complete reciprocal sperm transfer, (ii) sperm transfer patterns and their relationship with activity role, and (iii) the timing of sperm storage and sperm digestion. We found that reciprocal sperm transfer was completed within the first 5 h of copulation, which is ∼2–3 h before the end of copulation. Sperm transfer was mainly sequential, meaning that one individual donated all his ejaculate before its partner started to reciprocate. The initiation of sperm transfer did not depend on the activity role. The presence of allosperm in the spermatheca before sperm transfer suggests that individuals remate before they are allosperm depleted. No sperm was digested during copulation but sperm digestion took place 0–72 h after copulation. Our results suggest that contact mate guarding is a likely manipulation strategy in S. putris , because partners cannot immediately remate. In addition, staying in copula after sperm transfer is completed seems to prevent the immediate digestion of sperm and therefore may promote sperm displacement and allosperm storage.     

Genomic regions involved in productivity of two interspecific poplar families in Europe. 2. Biomass production and its relationships with tree architecture and phenology

Short-rotation coppice of hybrid poplar is a promising renewable feedstock for biofuel production. Breeding for high biomass in short-rotation coppice has started only recently. Two hybrid poplar families were grown at two sites in Europe and phenotyped for a variety of biomass-related traits (1) to examine the extent of phenotypic and genetic variation in biomass production, ramification, resprouting, and phenology, (2) to search for genomic regions involved in productivity, and (3) to determine the effect of the environment on the expression of these traits. The performance of both families differed within and among sites. A pronounced heterosis was observed in most cases. Moderate to high heritability values were found. Seventeen quantitative trait loci (QTL) for biomass production, 13 for ramification, ten for resprouting, 21 for bud burst, and ten for bud set were identified. Genetic correlations and QTL colocation showed that high wood production was associated with high allocation of wood into branches and with high production of resprouts after coppicing. Correlations and QTL colocation between biomass production and phenology traits were weak. Our study provides valuable information on genomic regions involved in biomass production, ramification, and phenology and on phenotypic and genetic relationships among these three trait categories.