Accumulation of an acidic dehydrin in the vicinity of the plasma membrane during cold acclimation of wheat

Expression of the acidic dehydrin gene wcor410 was found to be associated with the development of freezing tolerance in several Gramineae species. This gene is part of a family of three homologous members, wcor410, wcor410b, and wcor410c, that have been mapped to the long arms of the homologous group 6 chromosomes of hexaploid wheat. To gain insight into the function of this gene family, antibodies were raised against the WCOR410 protein and affinity purified to eliminate cross-reactivity with the WCS120 dehydrin-like protein of wheat. Protein gel blot analyses showed that the accumulation of WCOR410 proteins correlates well with the capacity of each cultivar to cold acclimate and develop freezing tolerance. Immunoelectron microscope analyses revealed that these proteins accumulate in the vicinity of the plasma membrane of cells in the sensitive vascular transition area where freeze-induced dehydration is likely to be more severe. Biochemical fractionation experiments indicated that WCOR410 is a peripheral protein and not an integral membrane protein. These results provide direct evidence that a subtype of the dehydrin family accumulates near the plasma membrane. The properties, abundance, and localization of these proteins suggest that they are involved in the cryoprotection of the plasma membrane against freezing or dehydration stress. We propose that WCOR410 plays a role in preventing the destabilization of the plasma membrane that occurs during dehydrative conditions.     

Populations Microbiennes Des Bois

Resumé Les auteurs ont étudié la composition chimique (N, substances humiques, lignine) de copeaux de bois blanc exposés à l'air libre depuis 2 à 10 ans, ainsi que leur type de peuplement fongique. En l'absence de lignivore, le pH, les taux de lignine et d'N s'élèvent et il se forme des quantités modérées d'humus à forte capacité d'échange. Dans le cas contraire, on voit apparaître, en abondance, des substances humiques peu condensées et la matière organique subit une évolution rappelant celle du mor.Avec la collaboration technique de Melle. M. Clet.Kononova, dans sa monographie⁵, signale de Troussov (1916) une étude que nous n'avons pas eu en mains.     

Plant powder teabags: a novel and practical approach to resolve culturability and diversity of rhizobacteria

We have developed teabags packed with dehydrated plant powders, without any supplements, for preparation of plant infusions necessary to develop media for culturing rhizobacteria. These bacteria are efficiently cultivated on such plant teabag culture media, with better progressive in situ recoverability compared to standard chemically synthetic culture media. Combining various plant‐based culture media and incubation conditions enabled us to resolve unique denaturing gradient gel electrophoresis (DGGE) bands that were not resolved by tested standard culture media. Based on polymerase chain reaction PCR‐DGGE of 16S rDNA fingerprints and sequencing, the plant teabag culture media supported higher diversity and significant increases in the richness of endo‐rhizobacteria, namely Gammaproteobacteria (Enterobacteriaceae) and predominantly Alphaproteobacteria (Rhizobiaceae). This culminated in greater retrieval of the rhizobacteria taxa associated with the plant roots. We conclude that the plant teabag culture medium by itself, without any nutritional supplements, is sufficient and efficient for recovering and mirroring the complex and diverse communities of rhizobacteria. Our message to fellow microbial ecologists is: simply dehydrate your plant canopy, teabag it and soak it to prepare your culture media, with no need for any additional supplementary nutrients.     

Chain-fluorinated polyamines as tumor markers--I. In vivo transformation of 2,2-difluoroputrescine into 6,6-difluorospermidine and 6,6-difluorospermine

1. Injection of 2,2-difluoroputrescine (DFPut) into the yolk sac of chick embryos causes the formation of 6,6-difluorospermidine (6,6DFSpd) and 6,6-difluorospermine (6,6DFSpm), demonstrating that the difluoroanalogs of putrescine and spermidine are in vivo substrates of spermidine and spermine synthase, respectively. 2. Depletion of tissue putrescine and spermidine concentrations by administration of D,L-alpha-difluoromethylornithine (DFMO, Ornidyl) causes a very marked enhancement of difluoropolyamine formation from DFPut. 3. The major accumulation of 6,6DFSpd and 6,6DFSpm in DFMO-pretreated rodents occurs in small intestines and tumors, i.e. in tissues with high cell proliferation rates, which are also the most susceptible to polyamine depletion by inhibition of ornithine decarboxylase. 4. Their preferential accumulation in tumors and the fact that DFPut and its metabolites seem not to exert toxic effects, suggest DFPut as a serious candidate for the use as probe in 19F-NMR imaging of tissues with a high proliferation rate and a high rate of polyamine biosynthesis.     

Polysome Metabolism during Cold Acclimation in Wheat

The content, composition and biological activity of polysomesfrom three wheat genotypes were studied during cold acclimation.The structural integrity of the different polysome populationswas not affected by the hardening temperature. Polysomes werealso found to accumulate at higher level in cold hardened seedlingssuggesting a high protein synthesis capacity during the acclimationperiod. The in vitro translation of polysome-bound mRNAs inthe wheat germ cell-free system showed a high translation potentialof polysomes from cold hardened seedlings compared to that ofcontrol. The electrophoretic analysis of the translation productsby two-dimensional SDS-PAGE revealed the induction of severalnew mRNAs in cold hardened wheat seedlings. The presence ofthese new messengers in the polysomal fraction suggests thatnew messages have already been processed, transported and preferentiallyselected for translation by the ribosomes. The most importantchange was the induction and pronounced synthesis of four peptides[one high mol wt peptide of 200 kDa (pI 6.5) and three smallerones of 58 (pI 7.0), 48 (pI 7.1) and 48 (pI 7.2) kDa respectively]in the freezing tolerant cultivar Norstar. These specific polypeptideswere absent in the freezing sensitive cultivar Glenlea suggestingthat their induction and expression was associated with thefreezing tolerance capacity. (Received January 19, 1990; Accepted August 24, 1990)     

High yield isolation of mesophyll protoplasts from wheat, barley and rye

Efficient procedures are described for high-yield isolation of mesophyll protoplasts from spring wheat ( Triticum aestivum L. cv. Glenlea), winter wheat ( Triticum aestivum L. cv. Frederick), barley ( Hordeum vulgare L. cv. Bruce) and rye ( Secale cereale L. cv. Puma). Factors such as plant age, composition of the incubation medium during isolation, purification procedures and culture medium affect protoplast yield, viability and metabolic competence, as measured by light-dependent CO₂ fixation. Optimal osmolarity of the isolation medium was equivalent to 1.8 times that measured in the leaves of all plant material used. The presence of 2 m M ascorbic acid in the preincubation and isolation medium increased the yield by 50% and conserved viability and metabolic competence. The protoplasts were stable for up to 48 h without loss of either viability or of original activity of CO₂ fixation, which was in the order of 100 μmol CO₂ (mg chl)⁻¹h⁻¹.
In our MC-56 liquid medium these protoplasts regenerated cell walls within 72 h and a few divided.     

Oxidative Damages and Repair in Euglena gracilis Exposed to Ozone. I. SH Groups and Lipids

Malondialdehyde, a product of lipid oxidation, increased graduallywhen Euglena gracilis cells were bubbled with 240 µ1.liter^–1ozone (delivery rate of 1µmolO₃.min^–1) for 120 min.Simultaneously, the sulfhydryl group content decreased by 36%during the treatment, which was mainly due to oxidation of proteinsulfhydryl groups. The molar amount of SH groups oxidized was3 times higher than that of fatty acid oxidized, indicatingthat sulfhydryl groups were more accessible or more easily oxidizedby O₃ than fatty acids. When Euglena cells were allowed to recoverunder autotrophic growth conditions following O₃ treatment,viable cells were incapable of dividing during the first 5 hof the recovery period but regenerated SH groups nearly to thecontrol level. The increase of SH content during this periodpreceded the resumption of cell division and the restorationof normal growth. These results suggest that the regenerationof SH groups by Euglena cells is a part of a mechanism involvedin the repair of oxidative damage caused by ozone and is anessential step for the initiation of cell division. (Received July 20, 1987; Accepted December 14, 1987)     

The level of trigonelline and other quaternary ammonium compounds in tomato leaves in ratio to the changing nitrogen supply

The choline, trigonelline, N-trimethyl-L-lysine content in the leaf tissue of tomato plants grown with varying amounts of nitrate nitrogen was determined by the OPLC method. The choline and trigonelline level in tomato leaves increased in direct ratio to the nitrogen supply. The possible role of these compounds in the physiology and in the augmented resistance of plants to nectrotizing stresses is discussed.     

Studies of esterase 6 in Drosophila melanogaster. XVIII. Biochemical differences between the slow and fast allozymes

Most natural populations of Drosophila melanogaster are polymorphic for two major electrophoretic variants at the esterase-6 locus. The frequency of the EST 6F allozyme is greatest in populations in warmer latitudes, whereas the EST 6S allozyme is predominant in colder latitudes. Latitudinal clines in electromorph frequencies are found on three continents. Purified preparations of the allozymes have been characterized for their pH optimum, substrate specificity, organophosphate inhibition, alcohol activation, thermal stability, and kinetic parameters. These and previous analyses of the EST 6 allozymes reveal that the two variants have differences in their physical and kinetic properties that may provide a basis for the selective maintenance of the polymorphisms and an explanation of the clinal variation observed in natural populations.