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S D Kung

Publications and source records attributed to S D Kung.

At least 37 records · Page 2Linked to original sources
PubMed1991

Possible repetitive DNA markers for Eusorghum and Parasorghum and their potential use in examining phylogenetic hypotheses on the origin of Sorghum species.

Genomic structures of two major species in section Eusorghum (Sorghum), Sorghum bicolor and Sorghum halepense, and their phylogenetic relationships with a species in section Parasorghum, Sorghum versicolor, were studied by using cloned repetitive DNA sequences from the three species. Of the five repetitive DNA clones isolated from S. bicolor and S. halepense, four produced qualitatively similar hybridization patterns with detectable variations in copy numbers of some of the restriction fragments on the Southern blots of the two genomic DNAs. One clone was shown to be diagnostic for S. halepense. Molecular analysis at the DNA level indicates that S. bicolor and S. halepense have similar but not identical genomes, consonant with differences in karyotypes, meiotic chromosome behaviors, morphology, and physiology of the species. In addition to five repetitive clones isolated from S. bicolor and S. halepense, eight more sequences were cloned from S. versicolor. Nine clones were found to be specific for either S. bicolor and S. halepense or S. versicolor. The remaining four had a moderate to strong homology with sequences present in all Sorghum species studied. We speculate that the genome in the common ancestor of Sorghum has differentiated to give rise to genomes of at least three major chromosome sizes; large, medium, and small, as seen at present. Amplifications, eliminations, rearrangements, and new syntheses of repetitive sequences may have been involved in genome differentiation of these species. The results also suggest that the S. versicolor genome has strongly diverged from the genomes of the two species in section Eusorghum.

Base Sequence↗
PubMed1990

Stem-loop structures at the 3' end of tobacco Rubisco large subunit mRNA.

There are two inverted repeat nucleotide (nt) sequences, each capable of forming a stem-loop structure (sls) at the 3' end of the tobacco Rubisco large subunit mRNA (rbcL). The smaller sls is followed by a larger sls. The in vivo functions of the 3' sls of the rbcL mRNA were characterized using the Escherichia coli system. S 1 mapping of the rbcL transcripts synthesized in E. coli revealed that the 3' end of a major transcript in the bacterial cell is almost identical to the 3' end of authentic chloroplast (cp) rbcL mRNA. This native 3' end is located 4 nt downstream from the larger sls for the cp mRNA and 6 nt for the bacterial transcript, respectively. Deletion experiments show that the larger sls is essential for producing the native 3' end of rbcL mRNA in E. coli. The sls do not function as an efficient transcription terminator but can stabilize upstream mRNA segments in vivo.

Base Sequence↗
PubMed1990

Restoration of shooty morphology of a nontumorous mutant of Nicotiana glauca x N. langsdorffii by cytokinin and the isopentenyltransferase gene.

The shooty morphology of a nontumorous amphidiploid mutant of Nicotiana glauca Grah. x N. langsdorffii Weinm. was restored by cytokinins, whether exogenously applied or endogenously produced by transformation of the mutant with a transfer DNA (T-DNA) cytokinin-biosynthesis gene (isopentenyltransferase; ipt). Auxins alone did not confer this effect. Similar transformation was not achieved for the parental species. In the case of transformation with the ipt gene, selection of the transformed tissues was based on its hormone-independent growth in the presence of the antibiotic kanamycin. Transformed tissues exhibited a shooty morphology, indistinguishable from that of wildtype genetic tumors N. glauca x N. langsdorffii. This altered phenotype was caused by the presence and constitutive expression of the ipt gene. The insertion and expression of this gene in transformed tissues was confirmed by using the polymerase chain reaction (PCR) technique as well as conventional molecular hybridization analysis. Expression of the ipt gene led to an elevated level of cytokinin in the transformed mutant tissues. This evidence supports the notion that genetic tumors are caused, at least in part, by elevated levels of cytokinin in interspecific hybrids.

Alkyl and Aryl Transferases↗
PubMed1986

Prokaryotic promoters in the chloroplast DNA replication origin of Chlamydomonas reinhardtii.

In Chlamydomonas reinhardtii, one displacement loop region which initiates the replication of chloroplast DNA was located on a 1.05 kb restriction fragment. This fragment was cloned and sequenced. In this report, the galK expression plasmid, pKO1 was used to screen for the presence of any prokaryotic promoter within the cloned fragment. The insertion of 2 AluI fragments yielded galK+ colonies. Sequence analyses of these AluI inserts revealed prokaryotic promoter consensus regions. Cloning into pKOTWI and subsequent DNA sequencing were used to determine the promoter-active orientation of each insert. Two back-to-back prokaryotic promoters were mapped on a 79 bp AluI fragment located within the displacement loop region.

Chlamydomonas↗
PubMed1985

Chloroplast promoters from higher plants.

This survey compiles 60 chloroplast promoter sequences from higher plants published to date and compares them with these sequences from procaryotic systems. The current evidence demonstrates that structurally defined chloroplast promoters are, in most cases, functionally active in initiating gene expression in chloroplasts.

Base Sequence↗
PubMed1985

Phytochrome control of levels of mRNA complementary to plastid and nuclear genes of maize.

The involvement of phytochrome in the control of the levels of RNA transcribed from maize plastid and nuclear genes was examined. The effects of illumination with red light, far-red light, or red light followed by far-red light on relative amounts of RNAs complementary to maize plastid genes for the large subunit of ribulose bisphosphate carboxylase (RuBPCase); the 32-kilodalton thylakoid membrane triazine herbicide binding B protein of photosystem II; the alpha, beta, and epsilon subunits of CF(1); subunit III (proton-translocating) of CF(0); the reaction center proteins A1 and A2 of photosystem I; two other light-induced genes for membrane proteins of photosystem II (ORFs 353 and 473); and one gene for an unidentified membrane protein (UORF 443) were measured by hybridization of labeled DNA probes to samples of leaf RNA. Transcripts of two nuclear-encoded genes, the genes for the small subunit of RuBPCase and the light-harvesting chlorophyll a/b binding protein, were studied in the same way. The levels of RNA complementary to all of these light-induced genes were significantly increased within 3 to 6 hours after brief illumination with red light. The stimulatory effects of red light were largely reversed by subsequent illumination with far-red light. It is concluded that phytochrome controls increases in the levels of mRNAs complementary to certain plastid and nuclear genes in dark-grown maize seedlings.

Journal Article↗
PubMed1984

The Nicotiana chloroplast genome. IX. Identification of regions active as prokaryotic promoters in Escherichia coli.

The galK-expression plasmid vector system pKO1 has been used to clone Nicotiana chloroplast (ct) promoters that function in Escherichia coli. The randomly cloned promoter-containing restriction fragments have been located on the ct genome and originate both from those regions encoding ribosomal and transfer RNAs and from locations elsewhere on the ct genome. The results provide the first demonstration that sequences which function as prokaryotic promoters exist in the ct genome.

Chloroplasts↗
PubMed1984

Light-induced transformation of amyloplasts into chloroplasts in potato tubers.

The transformation of amyloplast into chloroplasts in potato (Solanum tuberosum L.) tuber tissue can be induced by light. Excised potato tuber discs illuminated with white light of 3000 lux began to synthesize chlorophyll after a lag period of 1 day, and continued to synthesize chlorophyll for 3 weeks. In this paper we present evidence, based on ultracentrifugal sedimentation and immunoprecipitation, that the light-mediated synthesis of Ribulose-1,5-bisphosphate carboxylase began 1 day after illumination with white light. When illuminated the chloroplasts isolated from light-grown potato tuber tissue incorporated [(35)S]methionine into polypeptides, one of which has been identified as the large subunit of Ribulose-1,5-bisphosphate carboxylase. These chloroplasts are functional as determined by O(2) evolution in the Hill reaction.

Journal Article↗
PubMed1983

Relationship between the Kinetic Properties and the Small Subunit Composition of Nicotiana Ribulose-1, 5-bisphosphate Carboxylase.

Genetic variability in the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCase) in several Nicotiana species has been characterized by isoelectric focusing patterns. This heritable variation provides an opportunity to examine the functional role of each of these subunits. In this study, specifically designed RuBPCase enzymes composed of identical large subunits but different small subunits were constructed in vivo by interspecific hybridization between the species N. sylvestris, N. tabacum, N. glauca, N. glutinosa, N. plumbaginifolia, and N. tomentosiformis. Small subunit polypeptides were combined to form a sequence of one, two, three, and four polypeptides with the large subunit of N. sylvestris. Kinetic properties of these hybrid enzymes were compared. No differences in the specific activity of either carboxylation or oxygenation nor in K(m) values for ribulose 1,5-bisphosphate, CO(2), or O(2) were detected among the RuBPCase enzymes from the various interspecific hybrids. Likewise, the ratio of carboxylation to oxygenation was constant.

Journal Article↗
PubMed1980

Relationship of Ribulose-1,5-bisphosphate Carboxylase-Oxygenase Specific Activity to Subunit Composition.

Ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBPCase, EC 4.1.1.39) was isolated from Nicotiana sylvestris and from two cultivars and three nuclear substitution lines of Nicotiana tabacum. Isoelectric focusing patterns, supported by amino acid analyses and tryptic peptide mapping, were used to divide these enzymes into two categories: (a) RuBPCase with variable large subunits and identical small subunits; and (b) RuBPCase with identical large but different small subunits. Specific activities for both the carboxylation and oxygenation reactions were determined for all six RuBPCase enzymes under standard conditions of activation and assay. High, intermediate, and low levels of carboxylase (880, 530, and 340 nanomoles HCO(3) (-) per milligram per minute) and oxygenase (66, 45, and 35 nanomoles O(2) per milligram per minute) activity were noted. The carboxylase to oxygenase ratios ranged from 9 to 14.

Journal Article↗
PubMed1977

Evolutionary conservation of chloroplast genes coding for the large subunits of fraction 1 protein.

Crystalline fraction 1 protein, obtained from four species of Nicotiana, have identical polypeptide compositions and isoelectric points. However, the tryptic peptide map of the large subunit of this protein from N. knightiana and N. paniculata differs from that of N. tomentosa and N. tomentosiformis. Since the large subunits of fraction 1 protein are coded by chloroplast DNA, the difference in their primary structure reflects the structural changes of the chloroplast genes containing the coding information. This indicates that the rate of mutation of chloroplast DNA seems to be higher than predicated from the analysis of isoelectric points of this protein.

Journal Article↗
PubMed1976

Effect of aminonucleoside on the stability of rat liver ribosomal RNA to heating.

High molecular weight ribosomal RNA has been isolated from normal rat liver and from the livers of rats treated with aminonucleoside. Melting curves of the rRNA from treated rat livers were shifted to higher temperatures. The melting temperatures were found to be 62.5 and 66 degrees C for normal and treated material respectively. The rRNA was heated at different temperatures and analysed by polyacrylamide gel electrophoresis. In both normal and treated material, the 18 S was more stable in the treated material when compared with the control material.

Animals↗