Progressive release of carboxylating enzymes during mechanical grinding of sugar cane leaves

Summary The progressive release of protein, chlorophyll, phenol oxidase activity and phenolic compounds during the mechanical disruption of sugar cane leaves has been correlated with the release of carboxylating enzymes. Enzymes of the photosynthetic carbon reduction cycle were released in parallel with chlorophyll, the bulk of which was recovered in grana-containing chloroplasts. PEP carboxylase activity followed the release of total protein. Increased activities of the carboxylating enzymes were obtained in the presence of thioglycollate. There is evidence that PEP carboxylase resides in the cytoplasm rather than in either type of chloroplast. These results are discussed in relation to the possible localisation of carboxylation reactions in the sugar cane leaf.     

Effects of some phenoloxidase inhibitors on chloroplasts and carboxylating enzymes of sugar cane and spinach

Summary A number of additives have been tested for their effects on o-diphenol: O₂ oxidoreductase activity of cane leaves. The most inhibitory compounds were thioglycollate, -mercaptoethanol, polyethylene glycol and bovine serum albumin. Sulphydryl (SH) compounds did not affect rates of photosynthetic CO₂ assimilation when used at concentrations below 10^-2 M. However, in the presence of Mn⁺⁺ ions they contributed to an O₂ consumption which masked photosynthetic O₂ evolution. Addition of SH compounds or of polymers to the grinding media increased rates of enzymic CO₂ assimilation in crude enzyme preparations from cane leaves, but did not affect rates of CO₂ assimilation in similar spinach preparations. Strong reducing agents, copper chelators, low O₂ tension and high pH were effective in reducing phenoloxidase activity, but presented problems in the isolation and assay of chloroplasts. The results are discussed in relation to (a) design of suitable media for preparation of active cane chloroplasts and (b) comparative studies of enzyme levels in plants of various genera.     

Release of enzymes from quiescent fibroblasts during ATP depletion

The association between ATP depletion and enzyme release from cells has been described in two different ways: as a more or less linear dependence, or with a threshold value below which the enzyme release will start. We have investigated the association between ATP depletion caused by various metabolic inhibitors and enzyme release on quiescent fibroblasts. We found that the enzyme release never started before the ATP had decreased to a critical low level. Addition of glucose to cells while ATP was still above this critical level led to a regeneration of ATP and enzyme release did not occur. If ATP was lowered to 35-40% and kept there for 24 h, the enzyme release was minimal. These results support the threshold theory for release of enzymes from cells.     

Isolation and identification of killer yeasts from sugar cane molasses

A total of 13 yeast strains were isolated from 10 samples of sugar cane molasses obtained from sugar mills in Mexico; nine of them were killer strains. There was at least one killer strain in every sample. The resulting species were the following: Torulaspora delbrueckii (2), Schizosaccharomyces pombe (7), Cryptococcus albidus var. albidus (1) and Saccharomyces cerevisiae (3). A new killer species is reported: Schizosaccharomyces pombe .     

Cell wall invertases from apex and callus tissues of sugar cane

Calluses were obtained from the stalk apex of sugar cane. Boththe stalk apex and callus tissues possessed firmly bound cellwall invertases. The invertases of each tissue were characterizedon the basis of their Km, optimum pH and the action of variousinhibitors. According to this characterization, the two tissuespossess different isoenzymes. Taking into account the presentisoenzymes and the known cell wall invertases from stalk tissue,we postulated a different pattern of isoenzymes for each organof the sugar cane. These differences suggest that the cell wallinvertases might be used as markers in studies of tissue differentiation. (Received May 27, 1980; )     

Sugar transformations associated with hexose transport in immature internodal tissue of sugar cane

After a 15 sec incubation in d-glucose-¹⁴C(U), 53–70% of the intracellular radioactivity in immature internodal tissue of sugarcane was in glucose-6-phosphate, and the remainder was in free glucose. Two unmetabolized glucose analogs, 2-deoxy-d-glucosce and 3-O-methyl-d-glucose, were transported at rates comparable to glucose but neither of these analogs was phosphorylated. Doubly-labeled d-glucose-1-¹⁴C-6-phosphate-³²P was dephosphorylated prior to deposition in the inner space, and ¹⁴C was transported into this tissue twice as rapidly as ³²P. It was also shown that ³²P in exogenously supplied glucose-6-³²P was not the source of phosphate for the intracellular synthesis of glucose-6-P. Galactose transport was similar to that of glucose in that the first major product recovered intracellularly was a phosphorylated sugar, i.e. ¹⁴C-galactose-1-P, when the tissue was incubated in d-galactose-¹⁴C(U). Although fructose, glucose, and galactose competed for transport into this tissue, free fructose and glucose predominated in the tissue extract after a 15-sce incubation in d-fructose-¹⁴C(U). This contrasted sharply, with the products of ¹⁴C-glucose transport which were comprised of phosphorylated sugars after 15 sec.     

Cell wall invertases from apex and callus tissues of sugar cane

Calluses were obtained from the stalk apex of sugar cane. Boththe stalk apex and callus tissues possessed firmly bound cellwall invertases. The invertases of each tissue were characterizedon the basis of their Km, optimum pH and the action of variousinhibitors. According to this characterization, the two tissuespossess different isoenzymes. Taking into account the presentisoenzymes and the known cell wall invertases from stalk tissue,we postulated a different pattern of isoenzymes for each organof the sugar cane. These differences suggest that the cell wallinvertases might be used as markers in studies of tissue differentiation. (Received May 27, 1980; )     

Sectors of liguleless-1 tissue interrupt an inductive signal during maize leaf development.

The ligule and auricles separate the blade and sheath of normal maize leaves and are absent in liguleless-1 (lg1) mutant leaves. We induced chromosome breakage using X-rays to create plants genetically mosaic for lg1. In genetically mosaic leaves, when an lg1 mutant sector interrupts the normal ligule, the ligule is often displaced basipetally on the marginal side of the sector. Therefore, lg1 mutant sectors not only fail to induce ligule and auricle, but are also disrupting some form of intercellular communication that is necessary for the normally coordinated development of the ligular region. Our data are consistent with a model in which an inductive signal originates near the midvein, cannot traverse the lg1 mutant sector, and reinitiates in the wild-type tissue across the sector toward the leaf margin. The lg1 gene product, therefore, appears to be required for the transmission of this signal and could be involved with reception.     

小型昆虫DNA提取时匀浆方法的改进

应用改进的方法方便地提取了高质量的单头蚜虫基因组DNA ,有助于解决小型昆虫研究工作中单头虫体的DNA提取困难问题     

Production of ethanol from sugar cane molasses by Zymomonas mobilis

Summary Zymomonas mobilis strains were compared with each other and with a Saacharomyces cerevisiae strain for the production of ethanol from sugar cane molasses in batch fermentations. The effect of pH and temperature on ethanol production by Zymomonas was studied. The ability of Z. mobilis to produce ethanol from molasses varied from one strain to another. At low sugar concentrations Zymomonas compared favourably with S. cerevisiae. However, at higher sugar concentrations the yeast produced considerably more ethanol than Zymomonas.     

The compartmentation of carboxylating and decarboxylating enzymes in guard cell protoplasts

Guard cell and mesophyll cell protoplasts of Vicia faba L. were purified and separated into cytoplasmic and plastid fractions by a selective silicone-oil filtration. Before fractionation, the protoplasts were ruptured by a low speed centrifugation through a narrow-aperture nylon net placed in a plastic vial. This protoplast homogenation and subsequently the silicone-oil fractionation offer the possibility of investigating the comparatmentation of the enzymatic carboxylating (ribulose bisphosphate carboxylase EC 4.1.1.39, phosphoenolpyruvate carboxylase EC 4.1.1.31, NAD⁺ and NADP⁺ linked malate dehydrogenase EC 1.1.1.37) and decarboxylating pathways of malic (malic enzyme EC 1.1.1.40, phosphoenolpyruvate carboxykinase EC 4.1.1.32, pyruvate orthophosphate dikinase EC 2.7.9.1) which occur during the swelling and shrinking of the guard cell protoplasts. A model is proposed which describes the transport processes of malic acid during the starch-malate balance as correlated to the volume changes of the protoplasts. As the enzymes and their compartmentation in the guard cell protoplasts seem to be consistent with those of crassulacean acid metabolism (CAM) plants, the metabolism of stomata and of CAM cells is compared.Abbreviations AQ anthraquinone-2-sulfonic acid - CAM Crassulacean acid metabolism - DCPIP_red 2,6-dichlorophenol-indophenol - DTT dithiothreitol - EDTA ethylendiamine tetraacetic acid - GAPDH glyceraldehyde-3-phosphate dehydrogenase - HEPES N-2-hydroxyethyl-piperazine-N-2-ethane sulphonic acid - MDH malante dehydrogenase - MES 2(N-morpholino) ethane sulphonic acid - OAA oxaloacetic acid - PEP phosphoenolpyruvate - PSI photosystem I - KuP₂ ribulose bisphosphate     

Mechanisms of biocontrol by Pantoea dispersa of sugar cane leaf scald disease caused by Xanthomonas albilineans

Albicidins, a family of phytotoxins and antibiotics produced by Xanthomonas albilineans , are important in sugar cane leaf scald disease development. The albicidin detoxifying bacterium Pantoea dispersa (syn. Erwinia herbicola ) SB1403 provides very effective biocontrol against leaf scald disease in highly susceptible sugar cane cultivars. The P. dispersa gene ( albD ) for enzymatic detoxification of albicidin has recently been cloned and sequenced. To test the role of albicidin detoxification in biocontrol of leaf scald disease, albD was inactivated in P. dispersa by site-directed mutagenesis. The mutants, which were unable to detoxify albicidin, were less resistant to the toxin and less effective in biocontrol of leaf scald disease than their parent strain. This indicates that albicidin detoxification contributes to the biocontrol capacity of P. dispersa against X. albilineans . Rapid growth and ability to acidify media are other characteristics likely to contribute to the competitiveness of P. dispersa against X. albilineans at wound sites used to invade sugar cane.     

Regulation of expression of carbon-assimilating enzymes by nitrogen in maize leaf

We have utilized the cellular differentiation gradient of the developed, youngest leaf to examine the regulation by nitrogen of levels of phosphoenolpyruvate carboxylase (PEPCase), pyruvate orthophosphate dikinase (PPDK), and ribulose 1,5-bisphosphate carboxylase in maize (Zea mays L.). The protein whose level regulated most preferentially by N availability was PEPCase, followed by PPDK, and the changes in level occurred most conspicuously at the photosynthetically maturing cells. Pulse and pulse-chase experiments to analyze photosynthetic fixation of [¹⁴C]CO₂ indicate that maize leaf primarily exploited a C₄-mode of photosynthetic fixation of carbon dioxide even under a selective reduction in levels of these proteins. The effects of N on the synthesis of these proteins and the accumulation of corresponding mRNAs during recovery from a deficiency were examined by pulse and pulse-chase labeling with [³⁵S]Met and by hybridization, respectively. The rate of turnover of PPDK was substantially higher than that of the other proteins. Results also showed that the reduced accumulation of PEPCase, as well as PPDK, under N deficiency could largely be accounted for a reduced level of synthesis of protein with a concomitant reduction in level of their mRNAs. This indicates that the N-dependent selective accumulation of these enzymes is primarily a consequence of level of its mRNAs.     

Composition of sugar cane,energy cane,and sweet sorghum suitable for ethanol production at Louisiana sugar mills

A challenge facing the biofuel industry is to develop an economically viable and sustainable biorefinery. The existing potential biorefineries in Louisiana, raw sugar mills, operate only 3 months of the year. For year-round operation, they must adopt other feedstocks, besides sugar cane, as supplemental feedstocks. Energy cane and sweet sorghum have different harvest times, but can be processed for bio-ethanol using the same equipment. Juice of energy cane contains 9.8% fermentable sugars and that of sweet sorghum, 11.8%. Chemical composition of sugar cane bagasse was determined to be 42% cellulose, 25% hemicellulose, and 20% lignin, and that of energy cane was 43% cellulose, 24% hemicellulose, and 22% lignin. Sweet sorghum was 45% cellulose, 27% hemicellulose, and 21% lignin. Theoretical ethanol yields would be 3,609 kg per ha from sugar cane, 12,938 kg per ha from energy cane, and 5,804 kg per ha from sweet sorghum.