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1

Allozyme genetic distances and evolutionary relationships in marsupials of North and South America

100%
Barrantes G. E., Daleffe L.
Acta Theriologica
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1999
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tom 44
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nr 3
AUozyme genetic distances and variability were studied by horizontal starch gel electrophoresis in 6 species of marsupials from North and South America representing 4 different genera. Twenty-one presumptive loci were assessed in a total of 151 specimens. Only 1 of 21 loci was found to be monomorphic in the whole sample. Phenetic and cladistic interspecific analysis coincided in rendering two sharply dif­ferentiated subgroups: one comprising species of the genus Didelphis Linnaeus, 1758 CD. marsupialis Linnaeus, 1758, D. virginiana Kerr, 1792 and D. albiventris Lund, 1840), and the other comprising Monodelphis dimidiata fWagner, 1847}, Lestodelphys halli (Thomas, 1921) and Lutreolina crassicaudata (Desmarest, 1804). No relationships between the bradytelic condition, the karyotype stability of this group, and genetic variability were found. On the other hand, the existence of species with brief life span such as Lestodelphys halli and Monodelphis dimidiata (Marmosini tribe) and species with long life span (Didelphini tribe) allowed us to test the hypothesis which correlates generation-time with genetic variability. We conclude that a general explanation for genetic variability must involve more than just generation-time,
2

Structure, catalytic activity and evolutionary relationships of 1-aminocyclopropane-1-carboxylate synthase, the key enzyme of ethylene synthesis in higher plants

84%
Jakubowicz M.
Acta Biochimica Polonica
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2002
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tom 49
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nr 3
Both ethylene and the enzymes of ethylene synthesis are subjects of intensive scien­tific investigation. The present review discusses structure, catalytic activity and evo­lutionary relationships of 1-aminocyclopropane-1-carboxylate synthase, identified for the first time in ripening tomato in 1979. This enzyme is responsible for the conver­sion of «S-adenosyl-L-methionine to 1-aminocyclopropane-1-carboxylic acid, which is the key step of ethylene synthesis in higher plants. The role of this enzyme (especially in the fruit ripening) was demonstrated in 1991 in transgenic tomato plants, express­ing 1-aminocyclopropane-1-carboxylate synthase antisense RNA. On the basis of mu- tagenesis and crystallization of the enzyme, new data were provided on the three-di­mensional structure and amino-acid residues which are critical for catalysis. The con­trol of ethylene production is of great interest for plant biotechnology because it can delay senescence and overmaturation. These processes are responsible for large loss of vegetables and fruit on storage. Detailed structural and biochemical data are neces­sary to help design 1-aminocyclopropane-1-carboxylate synthase inhibitors, whose ap­plication is expected to have immense agricultural effects.
3

Evolutionary relationships of Ctenomys [Rodentia: Octodontidae] from Argentina, based on penis morphology

84%
Balbontin J., Reig S., Moreno S.
Acta Theriologica
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1996
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tom 41
|
nr 3
Analyses of qualitative and quantitative variation in bacula and soft parts of the glans penis of 13 species of Ctenomys Blainville, 1926 from Argentina were used to suggest systematic and evolutionary relationships. The 13 species can be divided into spike-bearing {C. australis, C. azarae, C. porteousi, C. rionegrensis, and C. talarum) and spiny bulb-bearing species {C. dorbignyi, C. pearsoni, C. perrensi, C. roigi, Ctenomys sp. from Curuzú Laurel, Ctenomys sp. from M. F. Mantilla, and Ctenomys sp. from San Roque). Ctenomys yolandae is unique because it shows both spikes and spiny bulbs. In addition to spikes and spiny bulbs, some populations of C. pearsoni, C. talarum, and C. yolandae had a new structure, an inner sac of the intromittent sac. The most frequent pattern of occurrence of spikes or spiny bulbs was 1-1 (one at each side of the urethra), an ancestral character state in caviomorphs. Variation in bacular dimensions was limited and differences among species were small, with the exception of C. pearsoni. This species showed a significantly short baculum with a wide base. Sperm and penial morphology suggests that C. talarum is the most plesiomorphic and C. yolandae the most derived species of this group. The pattern of geographic variation among these 13 species rejects the hypothesis of penis morphology contributing to reproductive isolation. Ctenomys pearsoni is the only species with some evidence of reproductive isolation resulting from penis morphology.
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