Role of Vacuolar Membrane Transport Systems in Plant Salinity Tolerance

About 20% of all irrigated land is adversely affected by salinity hazards and therefore understanding plant defense mechanisms against salinity will have great impact on plant productivity. In the last decades, comprehension of salinity resistance at molecular level has been achieved through the identification of key genes encoding biomarker proteins underpinning salinity tolerance. Implication of the vacuolar transport systems in plant salinity tolerance is one example of these central mechanisms rendering tolerance to saline stress. One important organelle in plant cells is the central vacuole that plays pivotal multiple roles in cell functioning under normal and stress conditions. This review thus attempts to address different lines of evidence supporting the role of the vacuolar membrane transport systems in plant salinity tolerance. Vacuolar transport systems include Na⁺(K⁺)/H⁺ antiporters, V-ATPase, V-PPase, Ca²⁺/H⁺ exchangers, Ca²⁺-ATPase, ion channels, aquaporins, and ABC transporters. They contribute essentially in retaining a high cytosolic K⁺/Na⁺ ratio, K⁺ level, sequestrating Na⁺ and Cl^? into vacuoles, as well as regulation of other salinity responsive pathways. However, little is known about the regulation and functions of some of the vacuolar transporters under salinity stress and therefore need more exploration and focus. Numerous studies demonstrated that the activities of the vacuolar transporters are upregulated in response to salinity stress, confirming their central roles in salinity tolerance mechanism. The second line of evidence is that manipulation of one of the genes encoding the vacuolar transport proteins results in some successful improvement of plant salinity tolerance. Therefore, transgene pyramiding of more than one gene for developing genotypes with better and strong salinity tolerance and productivity should gain more attention in future research. In addition, we should move step further and verify the experimental data obtained from either a greenhouse or controlled environment into field trials in order to support our claims.

     

Effect of prebiotic mannan oligosaccharide on hematological and blood serum biochemical parameters of cultured juvenile great sturgeon (Huso huso Linnaeus, 1754)

The nutritional effects of prebiotic mannan oligosaccharide were evaluated using hematological and blood serum biochemical parameters in cultured juvenile great sturgeon (Huso huso). Fish were offered formulated diets containing two levels of prebiotic mannan oligosaccharide (2 and 4 g kg^?1); a basal diet with no prebiotics was used as control. The experiment lasted for 46 days. Blood samples were collected from the caudal veins of 18 apparently healthy fish (average weight 217.77 ± 29.8 g) at the end of the trial. No significant differences were found in the serum enzyme activity levels between treatments (P > 0.05). However, adding mannan oligosaccharide as a supplement to the basal diet resulted in significant differences in lymphocytes and eosinophils between the control and the 2 g kg^?1 treatment (P < 0.05) as well as a significant difference in the creatinine factor in the 2 g kg^?1 mannan oligosaccharide treatment (P < 0.05). The results show that it would be advantageous to add 2 g kg^?1 mannan oligosaccharide to the diets of juvenile great beluga sturgeon (Huso huso).     

Production of growth hormones inCasuarina cunninghamiana root nodules induced byFrankia strain HFPCgI4

Summary Measurements of auxin and cytokinin activities in extracts ofCasuarina root nodules were made. The nodules were induced either by pure culture ofFrankia strain CgI4 or by crushed nodule inoculum. Levels of cytokinin activity were significantly higher in root nodules induced by pureFrankia culture than in those induced by crushed nodule inoculum. However, the reasons for this are unknown. Seasonal variation in levels of cytokinin activity inCasuarina nodules has also been detected.Dedicated to the memory of Professor John G. Torrey     

Dynamic measurement of the viscoelastic properties of skin

A wave propagation technique was used to measure the dynamic viscoelastic properties of excised skin when subjected to a low incremental strain. The propagation velocity, attenuation, and storage and loss moduli were determined from measured characteristics of a pulse propagating along a strip of skin. Experiments were conducted with the skin subjected to static stresses of 1500 Pa and 20,000 Pa. At low static stresses the skin response was viscoelastic with a loss tangent of approximately 0.6. In the frequency range of 0-1000 Hz, the wave velocity was relatively constant while the attenuation increased roughly linearly with frequency. However, results depended on the static stress. At the higher stress level the velocity was greater and the attenuation less than at the lower stress. At low stresses both the storage and loss moduli were relatively constant over the frequency range tested. The strong viscoelastic behavior of the tissue at higher frequencies is not predicted from models of the tissue determined from quasi-static test methods. In selecting a model to describe the behavior of skin, the test methods used for establishing the model must be consistent with its intended application.     

Serological characterization and partial purification of an Lyt-1 homolog in tunicate hemocytes.

A panel of alloantisera and monoclonal antibodies specific to murine Lyt-1 allotypic and framework determinants was used in indirect immunofluorescence and FACS analysis to investigate the occurrence of an Lyt-1 homolog in tunicate (protochordate) hemocytes. Binding assays and quantitative absorption experiments established the expression of Lyt-1 cross-reacting determinants on a distinct population of tunicate hemocytes. These determinants were expressed exclusively by cells with the morphological characteristics of hemoblasts and lymphocytes. In a rapid two-step purification procedure, Lyt-1 glycoproteins from tunicate hemocytes and C57B1/6 mouse thymocytes were solubilized and partially purified by affinity chromatography using a mAb anti-Lyt-1 frame-work determinant. In both cell types, antigenic activities were associated with a major 67-kDa component. Our findings suggest an early phylogenetic emergence of an Lyt-1 homolog at this level of evolution.     

Plant Viruses Affecting Tomatoes in Jordan. Identification and Prevalence

A survey was conducted during the period 1979–1982 to identify viruses affecting tomatoes in the Jordan Valley. Results indicated the rare occurrence of mosaic diseases caused by tobacco mosaic virus, cucumber mosaic virus, or potato virus Y. However, tomato yellow leaf curl virus was predominant.