Phyllotaxis in the Oil Palm: Applications in Selection of Interspecific Hybrids

The main purpose of the investigation was to determine whethermeasures associated with or dependent on the differences inphyllotaxis organization of the stem, fronds, and inflorescencesof three families of oil palms which differ considerably ingrowth habit and genetic background could be associated with,or allow prediction of their yield differences. Two of the familiesused are interspecific crosses between Elaeis guineensis andE. melanococca and these hybrids yield almost double that ofthe third ‘family’ (a group of E. guineensis selections)and have about twice the individual frond areas, inflorescencevolume, and surface area and about half the rate of verticalgrowth; they have, however, a slightly slower rate of frondand inflorescence production. One of the views expressed isthat the phyllotaxis organization which determines the measuredreduction of stem volume in the interspecific crosses is associatedwith the greater development of more productive reproductiveelements. Further, it is suggested that measurements of frond(even in the juvenile stage) and both male and female inflorescenceorganization could be used in yield prediction for these familiesand possibly other genetic groups-and thus increase the speedand efficiency of genetic selection.     

Study of the role of lysine residues of the cholesterol hydroxylating cytochrome P-450 by a method of chemical modification

Chemical modification of cytochrome P-450scc by lysine-specific reagents has been performed. Modification of the hemoprotein was shown to result in the loss of its ability to interact with adrenodoxin. With a view of identifying lysine residues involved in the interaction with adrenodoxin, cytochrome P-450scc was modified by succinic anhydride in the presence of adrenodoxin. After the removal of ferredoxin, the modification was performed with the use of a radioactively labeled reagent. Subsequent hydrolysis of the succinic hemoprotein by chymotrypsin and separation of the peptides obtained by high pressure liquid chromatography resulted in the isolation of seven chymotryptic peptides containing labeled lysine residues. These amino acid sequences were identified. The role of lysine residues of cytochrome P-450scc in complex formation with adrenodoxin is discussed.     

Molecular organization of the reductase complex in adrenal cortex mitochondria. Study using bifunctional reagents

The water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, homobifunctional reagent 3,3'-dithiobis (succinimidyl propionate), and heterobifunctional reagent N-succinimidyl 3-(2-pyridyldithio) propionate have been used to cross-link adrenodoxin reductase and adrenodoxin, components of steroidogenic electron transfer system. Though maximal yield of the cross-linked complex was achieved with the water-soluble carbodiimide, this complex was inactive in the electron transfer from NADPH to cytochrome P-450. The functionally active complex was formed with N-succinimidyl 3-(2-pyridyldithio) propionate. The complex was purified to the apparent homogeneity and shown to be able to mediate the electron transfer. The data obtained indicate existence of different binding sites on adrenodoxin responsible for the adrenodoxin reductase and cytochrome P-450scc binding and do not contradict to the model of the steroidogenic electron transfer in an organized complex.     

Phylogeographic structure in mitochondrial DNA of a South-east Asian freshwater fish, Hemibagrus nemurus (Siluroidei; Bagridae) and Pleistocene sea-level changes on the Sunda shelf

We postulated that the biogeographical history of South-east Asia contributed to extensive admixture during Pleistocene low sea levels of genetic groups of an obligate freshwater fish (the river catfish, Hemibagrus nemurus) isolated during periods of high sea levels. During Pleistocene glacial maxima, the sea level was lower than at present and the islands of the Sunda shelf (Sumatra, Borneo and Java) and the Asian mainland were connected by lowlands traversed by rivers. Restriction fragment length polymorphisms in mitochondrial DNA were documented for 140 putative H. nemurus analysed from 13 sampling sites resulting in the definition of 35 haplotypes. The high level of haplotype differentiation (mean P × 100 = 2.22, SD = 1.33) indicates that the subdivision of the ancestral H. netnurus group was extensive and probably occurred early in the Pleistocene. The occurrence of some genetically divergent groups of the H. netnurus complex occurring in sympatry in widely separated locations supports the proposition that low sea levels aided the dispersion and mingling of genetic groups. Based on both genetic and morphological evidence, the main H. nemurus line gave rise to three regional groups: (1) a morphologically distinct ‘Indochinese’ group composed of two mtDNA clades overlapping in east peninsular Malaysia; (2) a ‘Sundaic’ group composed of various lineages of differing morphology and genetic identity; (3) a genetically distinct ‘Sarawak’ group in west Borneo, similar in morphology to the ‘Sundaic’ and ‘Indochinese’ groups, but including a small, golden colour morph as a distinct dade. The morphologically similar Sundaic forms from west Java, Sumatra and west Borneo show some degree of genetic divergence, but their phylogenetic relationships are poorly resolved. The most genetically and morphologically distinct Sundaic dade, assigned to H. hoevenii, colonized the Kapuas river (west Borneo), east Sumatra and south peninsular Malaysia. Contrary to our original hypothesis and present biogeographical theory, little exchange of genetic groups has apparently occurred between the mainland and the Sunda Islands during recent glaciations.     

Comparison of the immunochemical properties of human placental and bovine adrenal cholesterol side-chain cleavage enzyme complex

The immunochemical relatedness between human and bovine proteins catalyzing the cholesterol side-chain cleavage reaction was investigated. In dot-immunobinding analysis, antibodies against bovine adrenocortical cytochrome P-450SCC, adrenodoxin, and adrenodoxin reductase recognized the corresponding proteins in a dose-dependent manner in mitochondrial preparations from human placenta. Limited proteolysis with trypsin cleaved bovine P-450SCC into fragments F1 and F2, which represent the NH2- and C-terminal parts of P-450SCC, respectively. Identical trypsin treatment yielded similar-size fragments from human placental P-450SCC. In Western immunoblots, anti-F1 and anti-F2 antibodies recognized the corresponding fragments in both trypsin-digested bovine and human P-450SCC. Antibodies against bovine P-450SCC, fragments F1 and F2, adrenodoxin and adrenodoxin reductase inhibited cholesterol side-chain cleavage activity in bovine adrenocortical mitochondria by 24-51%, but failed to affect the activity in human placental mitochondria. These data indicate that human and bovine P-450SCC share common antigenic determinants located outside the enzyme active site. The immunological similarity between bovine adrenodoxin and human ferredoxin allowed for a simple purification protocol of human placental P-450SCC by adrenodoxin affinity chromatography. The P-450SCC obtained by this method was electrophoretically homogeneous and showed characteristics typical to P-450SCC.