The control of root growth by reactive oxygen species in Salix nigra Marsh. seedlings.

The production of reactive oxygen species (ROS) in specific regions of Salix seedlings roots seems essential for the normal growth of this organ. We examined the role of different ROS in the control of root development in Salix nigra seedlings, and explored possible mechanisms involved in the regulation of ROS generation and action. Root growth was not significantly affected by OH quenchers, while it was either partially or completely inhibited in the presence of H2O2 or O2·â» scavengers, respectively. O2·â» production was elevated in the root apex, particularly in the subapical meristem and protodermal zones. Apical O2·â» generation activity was correlated to a high level of either Cu/Zn superoxide dismutase protein as well as carbonylated proteins. While NADPH-oxidase (NOX) was probably the main source of O2·â» generation, the existence of other sources should not be discarded. O2·â» production was also high in root hairs during budding, but it markedly decreased when the hair began to actively elongate. Root hair formation increased in the presence of H2O2 scavengers, and was suppressed when H2O2 or peroxidase inhibitors were supplied. The negative effect of H2O2 was partially counteracted by a MAPKK inhibitor. Possible mechanisms of action of the different ROS in comparison with other plant model systems are discussed.

On the nature and origin of the oxalate package in Solanum sisymbriifolium anthers.

This is a detailed study carried out in Solanum sisymbriifolium Lam. on the development of the circular cell cluster (CCC) during crystal deposition, as well as the composition of the crystals. Light microscopy and scanning and transmission electron microscopy (TEM) were used to characterize tissue throughout anther development. Energy dispersive X-ray analysis (EDAX) allowed the determination of the elemental composition of crystals that form in the CCC region, and infrared and x-ray diffraction analysis were used to specify the crystal salt composition. TEM analysis revealed that the crystals originated simultaneously within the vacuoles in association with a paracrystalline protein. Prior to the appearance of protein within vacuoles, protein paracrystals were visible in both rough endoplasmic reticulum and vesicles with ribosomes on their membranes. In vacuoles, paracrystals constitute nucleation sites for druse crystals formation. EDAX revealed that C, O, and Ca were the main elements, and K, Cl, Mg, P, S, and Si, the minor elements. X-ray powder diffraction of crystals detected the predominant presence of calcium oxalate, but also vestiges of calcite, quartz, and sylvite. The calcium oxalate coexisted in the three chemical forms, that is, whewellite, weddellite, and caoxite. Infrared spectrophotometry identified bands that characterize O-C-O, H-O, C-H bonds, all of calcium oxalate, and Si-O-Si, of quartz. These results were compared with studies of anthers carried out in other Solanaceae genera.

Storage lipids and proteins of Euterpe edulis seeds.

Comparative studies on fatty acid and protein composition of the endosperm and embryo of palmito (Euterpe edulis Martius) were conducted using gas-liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On a dry weight basis, the embryo contained extremely lower amounts of lipids and proteins than did the endosperm, which was associated with the scarce lipid and protein bodies previously reported in axis and cotyledon. The fatty acid composition also exhibited differences between both tissues: (I) the fatty acid diversity was greater in embryo than in endosperm; (II) embryo and endosperm contained predominantly linoleic, palmitic, oleic and stearic acids even though the relative values were different for each tissue. As compared to other palm species, the higher fatty acid unsaturation in Euterpe edulis seed could be involved in the previously reported short longevity and recalcitrant behavior during storage. Proteins of both tissues were heterogeneous in molecular mass. Some proteins were tissue-specific, but other were common, among them a highly glycosylated protein which migrated at about 55 kDa. We hypothesize that the latter, also reported in all previously studied palm species, is one of the proteins characterizing the Arecaceae family.

A cytoplasmically inherited barley mutant is defective in photosystem I assembly due to a temperature-sensitive defect in ycf3 splicing.

A cytoplasmically inherited chlorophyll-deficient mutant of barley (Hordeum vulgare) termed cytoplasmic line 3 (CL3), displaying a viridis (homogeneously light-green colored) phenotype, has been previously shown to be affected by elevated temperatures. In this article, biochemical, biophysical, and molecular approaches were used to study the CL3 mutant under different temperature and light conditions. The results lead to the conclusion that an impaired assembly of photosystem I (PSI) under higher temperatures and certain light conditions is the primary cause of the CL3 phenotype. Compromised splicing of ycf3 transcripts, particularly at elevated temperature, resulting from a mutation in a noncoding region (intron 1) in the mutant ycf3 gene results in a defective synthesis of Ycf3, which is a chaperone involved in PSI assembly. The defective PSI assembly causes severe photoinhibition and degradation of PSII.

Storage lipids and proteins of Euterpe edulis seeds

Comparative studies on fatty acid and protein composition of the endosperm and embryo of palmito (Euterpe edulis Martius) were conducted using gas-liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On a dry weight basis, the embryo contained extremely lower amounts of lipids and proteins than did the endosperm, which was associated with the scarce lipid and protein bodies previously reported in axis and cotyledon. The fatty acid composition also exhibited differences between both tissues: (I) the fatty acid diversity was greater in embryo than in endosperm; (II) embryo and endosperm contained predominantly linoleic, palmitic, oleic and stearic acids even though the relative values were different for each tissue. As compared to other palm species, the higher fatty acid unsaturation in Euterpe edulis seed could be involved in the previously reported short longevity and recalcitrant behavior during storage. Proteins of both tissues were heterogeneous in molecular mass. Some proteins were tissue-specific, but other were common, among them a highly glycosylated protein which migrated at about 55 kDa. We hypothesize that the latter, also reported in all previously studied palm species, is one of the proteins characterizing the Arecaceae family.

Storage lipids and proteins of Euterpe edulis seeds

Comparative studies on fatty acid and protein composition of the endosperm and embryo of palmito (Euterpe edulis Martius) were conducted using gas-liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On a dry weight basis, the embryo contained extremely lower amounts of lipids and proteins than did the endosperm, which was associated with the scarce lipid and protein bodies previously reported in axis and cotyledon. The fatty acid composition also exhibited differences between both tissues: (I) the fatty acid diversity was greater in embryo than in endosperm; (II) embryo and endosperm contained predominantly linoleic, palmitic, oleic and stearic acids even though the relative values were different for each tissue. As compared to other palm species, the higher fatty acid unsaturation in Euterpe edulis seed could be involved in the previously reported short longevity and recalcitrant behavior during storage. Proteins of both tissues were heterogeneous in molecular mass. Some proteins were tissue-specific, but other were common, among them a highly glycosylated protein which migrated at about 55 kDa. We hypothesize that the latter, also reported in all previously studied palm species, is one of the proteins characterizing the Arecaceae family.(AU)

The barley plastome mutant CL2 affects expression of nuclear and chloroplast housekeeping genes in a cell-age dependent manner.

The barley plastome mutant CL2 (cytoplasmic line 2) carries a point mutation in the infA gene, a homologue of the bacterial gene for the conserved translation initiator factor 1 (IF1). The function of infA in plastids is not known. The mutation in CL2 leads to a temporal chlorophyll deficiency in the primary leaf blade that is normalised in the basal and middle parts during further development. We have compared the expression of selected nuclear and plastid genes in different parts of primary leaves of CL2 and wild-type and found no indication for an adverse effect of the mutation on plastidial transcription. We observed an enhanced expression of RpoTp (encoding the phage-type nuclear-encoded plastid RNA polymerase) suggested to be caused by retrograde plastid signalling. Decreased amounts of plastid rRNA in basal and top sections are in agreement with the idea that the mutation in infA leads to a time- and position-dependent defect of plastid translation that causes a delay in plastid development. The normalisation of the phenotype in the middle section of CL2 leaves correlates with wild-type levels of chloroplast 16S rRNA and RbcL and increased expression of plastid housekeeping genes. The normalisation was not observed in cells at the tip of CL2 leaves suggesting different ways of regulating chloroplast development in cells at the tip of primary barley leaves as compared with other leaf sections.

Effects of desiccation on Euterpe edulis Martius seeds

Information on desiccation sensitivity of Euterpe edulis seeds under two drying rates is presented. The sensitivity was studied during the course of germination and normal germination. The water content was evaluated for both seeds and embryos. Results showed the following: (a) For both drying treatments and for both germination and normal germination, desiccation sensitivity values were higher for measurements based on the water content of the embryo than for those of the seed. (b) For both drying treatments, desiccation sensitivity were higher for normal germination than for germination based on both the embryo and seed water contents. (c) Under the slow drying treatment and for measurements based on the seed water content, critical water content was visible for normal germination but not for germination; (d) Critical water contents for germination and normal germination were more clearly established in the fast drying treatment than they were in the slow drying method based on both the embryo and seed water contents. Critical water contents were not associated with changes in electrolyte leakage, which suggests that conductivity is not a good indicator of physiological seed quality. From the beginning of both drying treatments, changes in nuclei and vacuoles were observed, but, when seed water content was reduced to below critical values, the cells became severely plasmolyzed, the vacuoles highly distorted, and the nuclei formed an almost homogeneous mass with the chromatin and the nucleoplasm, which suggests irreversible DNA damages.

Effects of desiccation on Euterpe edulis Martius seeds

Information on desiccation sensitivity of Euterpe edulis seeds under two drying rates is presented. The sensitivity was studied during the course of germination and normal germination. The water content was evaluated for both seeds and embryos. Results showed the following: (a) For both drying treatments and for both germination and normal germination, desiccation sensitivity values were higher for measurements based on the water content of the embryo than for those of the seed. (b) For both drying treatments, desiccation sensitivity were higher for normal germination than for germination based on both the embryo and seed water contents. (c) Under the slow drying treatment and for measurements based on the seed water content, critical water content was visible for normal germination but not for germination; (d) Critical water contents for germination and normal germination were more clearly established in the fast drying treatment than they were in the slow drying method based on both the embryo and seed water contents. Critical water contents were not associated with changes in electrolyte leakage, which suggests that conductivity is not a good indicator of physiological seed quality. From the beginning of both drying treatments, changes in nuclei and vacuoles were observed, but, when seed water content was reduced to below critical values, the cells became severely plasmolyzed, the vacuoles highly distorted, and the nuclei formed an almost homogeneous mass with the chromatin and the nucleoplasm, which suggests irreversible DNA damages.(AU)