Integration of molecular and physiological models to explain time of anthesis in wheat

Background and Aims

A model to predict anthesis time of a wheat plant from environmental and genetic information requires integration of current concepts in physiological and molecular biology. This paper describes the structure of an integrated model and quantifies its response mechanisms.

Methods

Literature was reviewed to formulate the components of the model. Detailed re-analysis of physiological observations are utilized from a previous publication by the second two authors. In this approach measurements of leaf number and leaf and primordia appearance of near isogenic lines of spring and winter wheat grown for different durations in different temperature and photoperiod conditions are used to quantify mechanisms and parameters to predict time of anthesis.

Key Results

The model predicts the time of anthesis from the length of sequential phases: 1, embryo development; 2, dormant; 3, imbibed/emerging; 4, vegetative; 5, early reproductive; 6, pseudo-stem extension; and 7, ear development. Phase 4 ends with vernalization saturation (VS), Phase 5 with terminal spikelet (TS) and Phase 6 with flag leaf ligule appearance (FL). The durations of Phases 4 and 5 are linked to the expression of Vrn genes and are calculated in relation to change in Haun stage (HS) to account for the effects of temperature per se. Vrn1 must be expressed to sufficient levels for VS to occur. Vrn1 expression occurs at a base rate of 0·08/HS in winter ‘Batten’ and 0·17/HS in spring ‘Batten’ during Phases 1, 3 and 4. Low temperatures promote expression of Vrn1 and accelerate progress toward VS. Our hypothesis is that a repressor, Vrn4, must first be downregulated for this to occur. Rates of Vrn4 downregulation and Vrn1 upregulation have the same exponential response to temperature, but Vrn4 is quickly upregulated again at high temperatures, meaning short exposure to low temperature has no impact on the time of VS. VS occurs when Vrn1 reaches a relative expression of 0·76 and Vrn3 expression begins. However, Vrn2 represses Vrn3 expression so Vrn1 must be further upregulated to repress Vrn2 and enable Vrn3 expression. As a result, the target for Vrn1 to trigger VS was 0·76 in 8-h photoperiods (Pp) and increased at 0·026/HS under 16-h Pp as levels of Vrn2 increased. This provides a mechanism to model short-day vernalization. Vrn3 is expressed in Phase 5 (following VS), and apparent rates of Vrn3 expression increased from 0·15/HS at 8-h Pp to 0·33/HS at 16-h Pp. The final number of leaves is calculated as a function of the HS at which TS occurred (TS^HS): 2·86 + 1·1 × TS^HS. The duration of Phase 6 is then dependent on the number of leaves left to emerge and how quickly they emerge.

Conclusions

The analysis integrates molecular biology and crop physiology concepts into a model framework that links different developmental genes to quantitative predictions of wheat anthesis time in different field situations.     

Variation in breeding success among reintroduced island populations of South Island Saddlebacks Philesturnus carunculatus carunculatus

South Island Saddlebacks Philesturnus carunculatus carunculatus were once found throughout the South Island of New Zealand, but by the early 1960s were confined to the island of Big South Cape, in the extreme south of the country. All subsequent reintroduced populations of South Island Saddlebacks are derived from 36 surviving birds from this relict population. The aim of this study was to compare the breeding success of three recently reintroduced populations of Saddlebacks relative to their distance from, and habitat similarity to, the relict population. The three study islands show a latitudinal cline with Ulva, Breaksea and Motuara Islands located 60, 190 and 810 km north of Big South Cape, respectively. Saddlebacks on Ulva and Breaksea appeared to prefer to establish breeding territories in coastal scrub, the dominant habitat feature of Big South Cape. The area of coastal scrub habitat was much smaller on Motuara, where breeding territories were instead scattered through broadleaf forest habitat. Nesting success, calculated using Mayfield's method, was significantly greater on Ulva (73%) than on Breaksea (32%) or Motuara (19%) owing primarily to higher egg fertility and hatching success. Although egg failure rates were highest on Motuara, the island least similar to Big South Cape, they were also relatively high on Breaksea where the habitat was similar to Ulva and Big South Cape. Therefore, the results only partially support the hypothesis that nesting success should decrease with increasing habitat difference associated with increasing latitudinal distance from the source population. The data from this 1-year study lay the groundwork for examining further hypotheses on the effects of reintroducing endangered species outside their contemporary range, but within their historical range.     

High swimming and metabolic activity in the deep-sea eel Synaphobranchus kaupii revealed by integrated in situ and in vitro measurements

Several complementary studies were undertaken on a single species of deep-sea fish (the eel Synaphobranchus kaupii) within a small temporal and spatial range. In situ experiments on swimming and foraging behaviour, muscle performance, and metabolic rate were performed in the Porcupine Seabight, northeast Atlantic, alongside measurements of temperature and current regime. Deep-water trawling was used to collect eels for studies of animal distribution and for anatomical and biochemical analyses, including white muscle citrate synthase (CS), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and pyruvate kinase (PK) activities. Synaphobranchus kaupii demonstrated whole-animal swimming speeds similar to those of other active deep-sea fish such as Antimora rostrata. Metabolic rates were an order of magnitude higher (31.6 mL kg(-1) h(-1)) than those recorded in other deep-sea scavenging fish. Activities of CS, LDH, MDH, and PK were higher than expected, and all scaled negatively with body mass, indicating a general decrease in muscle energy supply with fish growth. Despite this apparent constraint, observed in situ burst or routine swimming performances scaled in a similar fashion to other studied species. The higher-than-expected metabolic rates and activity levels, and the unusual scaling relationships of both aerobic and anaerobic metabolism enzymes in white muscle, probably reflect the changes in habitat and feeding ecology experienced during ontogeny in this bathyal species.     

Atypical protein kinase Ciota plays a critical role in human lung cancer cell growth and tumorigenicity

Atypical protein kinase C (aPKC) isozymes function in epithelial cell polarity, proliferation, and survival and have been implicated in cellular transformation. However, the role of these enzymes in human cancer is largely unexplored. Here, we report that aPKCiota is highly expressed in human non-small cell lung cancer cell lines, whereas the closely related aPKC isozyme PKCzeta is undetectable in these cells. Disruption of PKCiota signaling reveals that PKCiota is dispensable for adherent growth of non-small cell lung cancer cells but is required for transformed growth in soft agar in vitro and for tumorigenicity in vivo. Molecular dissection of signaling down-stream of PKCiota demonstrates that Rac1 is a critical molecular target for PKCiota-dependent transformation, whereas PKCiota is not necessary for NFkappaB activation in vitro or in vivo. Expression of the PB1 domain of PKCiota (PKCiota-(1-113)) blocks PKCiota-dependent Rac1 activity and inhibits cellular transformation indicating a role for this domain in the transforming activity of PKCiota. Taken together, our data demonstrate that PKCiota is a critical lung cancer gene that activates a Rac1-->Pak-->Mek1,2-->Erk1,2 signaling pathway required for transformed growth. Our data indicate that PKCiota may be an attractive molecular target for mechanism-based therapies for treatment of lung cancer.     

Specific inhibition of the plasmodial surface anion channel by dantrolene

The plasmodial surface anion channel (PSAC), induced on human erythrocytes by the malaria parasite Plasmodium falciparum, is an important target for antimalarial drug development because it may contribute to parasite nutrient acquisition. However, known antagonists of this channel are quite nonspecific, inhibiting many other channels and carriers. This lack of specificity not only complicates drug development but also raises doubts about the exact role of PSAC in the well-known parasite-induced permeability changes. We recently identified a family of new PSAC antagonists structurally related to dantrolene, an antagonist of muscle Ca++ release channels. Here, we explored the mechanism of dantrolene's actions on parasite-induced permeability changes. We found that dantrolene inhibits the increased permeabilities of sorbitol, two amino acids, an organic cation, and hypoxanthine, suggesting a common pathway shared by these diverse solutes. It also produced parallel reductions in PSAC single-channel and whole-cell Cl- currents. In contrast to its effect on parasite-induced permeabilities, dantrolene had no measurable effect on five other classes of anion channels, allaying concerns of poor specificity inherent to other known antagonists. Our studies indicate that dantrolene binds PSAC at an extracellular site distinct from the pore, where it inhibits the conformational changes required for channel gating. Its affinity for this site depends on ionic strength, implicating electrostatic interactions in dantrolene binding. In addition to the potential therapeutic applications of its derivatives, dantrolene's specificity and its defined mechanism of action on PSAC make it a useful tool for transport studies of infected erythrocytes.     

Recovery and Characterization of a 30.7-kDa Protein from Bacillus licheniformis Associated with Inhibitory Activity Against Methicillin-Resistant Staphylococcus aureus, Vancomycin-Resistant Enterococci, and Listeria monocytogenes

Of 131 bacterial isolates from seaweed, a culture of Bacillus licheniformis produced a novel protein with antibacterial activity against methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and Listeria monocytogenes. The antibacterial activity was maximal in cultures prepared in Columbia broth containing pieces of synthetic polyurethane sponge and shaken at 210 to 230 rpm. Antibacterial activity was not found in cultures grown statically or with different speeds of rotary shaking. Reduced activity was apparent in supernatants prepared from marine 2216E broth and tryptone soya broth with or without 1% (wt/vol) sodium chloride. The antibacterial compound was sensitive to proteinase K, pronase, and trypsin, but was not affected by Tween−20, −40, −60, or −80, or α− or β-amylase. Activity was not adversely affected by heating up to 40°C or treatment at pH 5 to 14. The bioactive compound was determined to be associated with a protein of 30.7 kDa, which had homology to the YbdN protein of B. licheniformis ATCC 14580.     

Early HLA-B*57-Restricted CD8+ T Lymphocyte Responses Predict HIV-1 Disease Progression

Although HLA-B*57 (B57) is associated with slow progression to disease following HIV-1 infection, B57 heterozygotes display a wide spectrum of outcomes, including rapid progression, viremic slow progression, and elite control. Efforts to identify differences between B57-positive (B57(+)) slow progressors and B57(+) rapid progressors have largely focused on cytotoxic T lymphocyte (CTL) phenotypes and specificities during chronic stages of infection. Although CTL responses in the early months of infection are likely to be the most important for the long-term rate of HIV-1 disease progression, few data on the early CTL responses of eventual slow progressors have been available. Utilizing the Multicenter AIDS Cohort Study (MACS), we retrospectively examined the early HIV-1-specific CTL responses of 14 B57(+) individuals whose time to development of disease ranged from 3.5 years to longer than 25 years after infection. In general, a greater breadth of targeting of epitopes from structural proteins, especially Gag, as well as of highly conserved epitopes from any HIV-1 protein, correlated with longer times until disease. The single elite controller in the cohort was an outlier on several correlations of CTL targeting and time until disease, consistent with reports that elite control is typically not achieved solely by protective HLA-mediated CTLs. When targeting of individual epitopes was analyzed, we found that early CTL responses to the IW9 (ISPRTLNAW) epitope of Gag, while generally subdominant, correlated with delayed progression to disease. This is the first study to identify early CTL responses to IW9 as a correlate of protection in persons with HLA-B*57.