Enhanced H Transport Capacity and ATP Hydrolysis Activity of the Tonoplast H-ATPase after NaCl Adaptation

Tonoplast enriched membrane vesicle fractions were isolated from unadapted and NaCl (428 millimolar) adapted tobacco cells (Nicotiana tabacum L. var Wisconsin 38). Polypeptides from the tonoplast enriched vesicle fractions were separated by SDS-PAGE and analyzed by Western blots using polyclonal antibodies to the 70 kilodalton subunit of the red beet tonoplast H⁺-ATPase. These antibodies cross-reacted exclusively to a tobacco polypeptide of an apparent molecular weight of 69 kilodaltons. The antibodies inhibited ATP-dependent, NO₃⁻ sensitive H⁺ transport into vesicles in tonoplast enriched membrane fractions from both unadapted and NaCl adapted cells. The relative H⁺ transport capacity per unit of 69 kilodalton subunit of the tonoplast ATPase of vesicles from NaCl adapted cells was fourfold greater than that observed for vesicles from unadapted cells. The increase in specific H⁺ transport capacity after adaptation was also observed for ATP hydrolysis.     

In vitro clonal propagation of dioecious Carica papaya

A procedure for in vitro propagation of dioecious papaya clones is described. A high rate of success in culture estbalishment was obtained when axillary buds were taken from lateral shoots of hedged rooted cuttings grown in a greenhouse. Seasonal endophytic contamination was suppressed by shaking propagules for 24 h in 300 mgl^-1 rifampicin or by incorporating it at 50 mgl^-1 into the medium. Murashige & Skoog (MS) basal medium supplemented with 0.5 mgl^-1 6-benzyladenine and 0.1 mgl^-1 naphthaleneacetic acid was used for establishment and proliferation. The addition of 160 mgl^-1 adenine sulfate improved multiplication and shoot growth. An elongation stage on MS medium supplemented with 1.0 mgl^-1 kinetin and 0.05 mgl^-1 naphthaleneacetic acid was necessary before rooting. Rooting was obtained at a high rate on half-strength macroelements of MS medium supplemented with 1.0 mgl^-1 indole-3-butyric acid. Commercial plots of papaya plants obtained through this procedure already exist.     

The Relationship Between Peroxidase Activity and Resistance to Sphaerotheca fuliginea in Melons

The levels of peroxidase activity in leaves of non-infected melon plants resistant to Sphaerotheca fuliginea (Schl. ex. Fr.) Poll. were considerably higher than those in the leaves of susceptible plants. After infection the ratio of peroxidase activity to that in non-infected plants reached a value of up to 47.5 in susceptible plants whereas in resistant plants it remained between 1 and 2. Changes in isozyme pattern were investigated by polyacrylamide gel electrophoresis. In non-infected resistant leaves slowly migrating isozymes were found. Their intensities increased with time following infection. These isozymes were absent in the susceptible leaves but appeared after the leaves had been infected with S. fuliginea. The role of these isozymes in the resistance mechanism is discussed.     

The Relationship Between Peroxidase Activity and the Resistance of Tomatoes (Lycopersicum esculentum) to Verticillium dahliae

The levels of peroxidase activity in roots of non-infected tomato plants resistant to Verticillium dahliae Kleb., were found to be considerably higher than those in the roots of susceptible plants. Similar differences were found in the leaves but were not significant as in the roots. Peroxidase activity increased in leaves, stems and roots of both susceptible and resistant plants after infection with V. dahliae. The ratio of the increase in leaves and roots of susceptible plants was greater than those of resistant plants. A positive correlation was found between the peroxidase activity in the roots of eleven cultivars/breeding lines and presence of Ve gene.     

Molecular dissection of Tomato leaf curl virus resistance in tomato line TY172 derived from Solanum peruvianum

Tomato yellow leaf curl virus (TYLCV) is devastating to tomato (Solanum lycopersicum) crops and resistant cultivars are highly effective in controlling the disease. The breeding line TY172, originating from Solanum peruvianum, is highly resistant to TYLCV. To map quantitative trait loci (QTLs) controlling TYLCV resistance in TY172, appropriate segregating populations were analyzed using 69 polymorphic DNA markers spanning the entire tomato genome. Results show that TYLCV resistance in TY172 is controlled by a previously unknown major QTL, originating from the resistant line, and four additional minor QTLs. The major QTL, we term Ty-5, maps to chromosome 4 and accounts for 39.7–46.6% of the variation in symptom severity among segregating plants (LOD score 33–35). The minor QTLs, originated either from the resistant or susceptible parents, were mapped to chromosomes 1, 7, 9 and 11, and contributed 12% to the variation in symptom severity in addition to Ty-5.     

Shoot regeneration from leaf explants of <Emphasis Type="Italic">Brunfelsia calycina</Emphasis>

A protocol for plantlet regeneration through shoot formation was developed for the neotropical shrub Brunfelsia calycina. This shrub is unique in its change in flower color from dark purple to white. Explants from young and mature leaves were incubated on MS medium (pH 5.7, 30 g/l sucrose, 7.5 g/l agar) with various combinations of Indole-3-acetic acid (IAA) and 6-Benzyladenine (BA) under a 16 h photoperiod at a constant temperature of 25°C. Shoot emergence was best at 4.44 μM BA and 2.85 μM IAA for young leaf explants, and at 8.88 μM BA, 2.85 μM IAA for mature leaf explants. When shoots were transferred to MS medium supplemented with 1.23–2.46 μM indole butrytic acid (IBA), they developed roots.     

Virulence and the Production of Endo-1,4-β-glucanase by Isolates of Alternaria alternata Involved in the Moldy-core Disease of Apples

Alternaria alternata, is the predominant fungal pathogen responsible for moldy‐core in apple cultivars of the Red Delicious group. Here we report on the association between virulence of natural isolates of A. alternata, their production of endo‐1,4‐β‐glucanase (EG) and moldy‐core development in apple fruits. Based on decay development following wound inoculations of mature fruits, three of 150 isolates, collected in three orchards in northern Israel and representing low, moderate and high virulence, were selected and designated Rm44, Er30 and Sh42, respectively. All three isolates secreted EG when grown on enzyme‐inducing medium (EIM) containing commercial cellulose or apple cell walls and this production was related to their degree of virulence. Polyacrylamide gel electrophoresis (PAGE) revealed quantitative differences between the three isolates, relative to their virulence. When fungal extracts were run in native gels, a single band with a molecular mass of 23 kDa showing EG activity was produced by the high‐ (Sh42) and the medium‐virulence (Er30) isolate but not by the low‐virulence (Rm44) isolate. A commercial cellulase preparation (containing endo‐ and exo‐1,4‐β‐glucanase) placed on pricked fruit led to the formation of symptoms similar to those developing on A. alternata‐inoculated fruits within 2–4 days. Inoculation of bloom clusters at full bloom with the highly virulent isolate (Sh42) of A. alternata resulted in a significantly higher infection in fruits (58%) than in those inoculated with the low‐virulence isolate (Rm44) (30%). Our results suggest that the moldy‐core symptoms caused by A. alternata in apple, could be related to the ability of the fungus to produce EG in developing lesions.     

Increased anthocyanin accumulation in aster flowers at elevated temperatures due to magnesium treatment

Temperature is one of the main external factors affecting anthocyanin accumulation in plant tissues: low temperatures cause an increase and elevated temperatures cause a decrease in anthocyanin concentration. Several metals have been shown to increase the half-life time of anthocyanins, by forming complexes with them. We studied the combined effect of elevated temperatures and increased metal concentrations on the accumulation of anthocyanins in aster 'Sungal' flowers. It has been found that magnesium treatment of aster plants or detached flower buds, partially prevents colour fading at elevated temperatures. Anthocyanin concentration of aster 'Sungal' flowers grown at 29°C/21°C day/night, respectively, was about half that of flowers grown at 17°C/9°C. The activity of phenylalanine ammonia-lyase (PAL) and chalcone isomerase (CHI) decreased as the temperature increased. Treatment of both whole plants and detached flower buds grown at elevated temperatures in the presence of magnesium salts, increased flower anthocyanin concentration by up to 80%. Measurement of magnesium following these treatments revealed an increased level of the metal in the petals, suggesting a direct effect. Magnesium treatment does not seem to cause increased synthesis of anthocyanin through a stress-related reaction, since the activities of both PAL and CHI did not increase due to this treatment. The results of this study show that increasing magnesium levels in aster petals prevents the deleterious effect of elevated temperatures on anthocyanin accumulation, thus enhancing flower colour.     

BiP, HSP70, NDK and PDI in wheat endosperm. II. Effects of high temperature on protein and mRNA accumulation

The effects of high temperature on accumulation of the 70‐kDa heat shock protein (HSP70) and nucleoside diphosphate kinase (NDK) as well as two other proteins that have roles in the biosynthesis of storage proteins were examined during grain development. An HSP70 homolog and a 17‐kDa NDK were co‐purified from wheat endosperm, their identity verified, and a cDNA for an HSP70 expressed in endosperm was isolated. Wheat plants ( Triticum aestivum , cvs Butte and Vulcan) were heat shocked at 40°C or exposed to maximum daily temperatures of 37 or 40°C during early or mid‐grain fill. Antibodies and cDNA probes for BiP, HSP70, NDK and PDI were used to examine the effect of high temperatures on the accumulation of protein and mRNA in the endosperm. HSP70 mRNA levels increased substantially when plants were exposed to heat shock or to a 1‐day gradual increase to 40°C. The effects of a 5‐day heat treatment on mRNA levels were more complicated and depended on the developmental stage of the grain. A treatment that began at 7 days post‐anthesis (DPA) decreased the level of mRNA for HSP70, BiP, PDI and NDK, whereas a treatment that began at 14 DPA slightly increased mRNA levels. The same treatments increased the accumulation of HSP70 but did not affect BiP, PDI, or NDK protein levels. This is the first detailed report on the effects of heat on mRNA and protein levels for HSP70 in a developing seed storage tissue.