Maintenance and Growth of the Horny Processes of the Medaka, Oryzias latipes, in Vitro

The maintenance and growth of the horny processes of the medaka, Oryzias latipes , were investigated in vitro by organ culture of the anal-fin. Processes were induced in adult females by oral administration of ethisterone. On this day, anal-fins were removed and cultured with in media containing androgen. Early processes elongated in these media during six to eight days of culture, though they degenerated in androgen-free control media. They developed to nearly the same degree as those in intact fins in medium 199 and CMRL-1066, while they degenerated to various extents in Eagle's MEM and Dulbecco's modified EM. These results suggest that scleroblasts maintain the mass and secrete the horny substance in vitro in the presence of androgen and essential nutrients. Early processes developed on the fifth day of treatment.     

DNA binding of citrus dehydrin promoted by zinc ion

Dehydrins are hydrophilic proteins that accumulate during embryogenesis and osmotic stress responses in plants. Here, we report an interaction between citrus dehydrin Citrus unshiu cold-regulated 15 kDa protein (CuCOR15) and DNA. Binding of CuCOR15 to DNA was detected by an electrophoretic mobility shift assay, a filter-binding assay and Southwestern blotting. The binding was stimulated by physiological concentrations of Zn²⁺, but little stimulation occurred when other divalent cations, such as Mg²⁺, Ca²⁺, Mn²⁺, Ni²⁺ and Cu²⁺, were substituted for Zn²⁺. Ethylenediaminetetraacetic acid cancelled the Zn²⁺-stimulated binding. A binding curve and competitor experiments suggested that the DNA binding of CuCOR15 exhibited low affinity and non-specificity. Moreover, tRNA competed with the DNA binding. Histidine-rich domains and a polylysine segment-containing domain participated in the DNA binding. These results suggest that CuCOR15 can interact with DNA, and also RNA, in the presence of Zn²⁺. Dehydrin may protect nucleic acids in plant cells during seed maturation and stress responses.     

THE ROLE OF THE SEED-COATS IN GERMINATION OF PHOTOSENSITIVE LETTUCE SEEDS

1. In order to analyze the role of both the fruit-coat and theendosperm in the germination of Grand Rapids lettuce seed andin the elongation of the embryo, the seeds were subjected toa number of operations. The fruit-coat was found to make onlya minor con tribution to the photosensitivity of the seed. Thefact that 100% germination of these seeds can occur in completedarkness, when the restraining influence of the endosperm isremoved by appropriate cuts, makes clear that it is the integrityof the endosperm layer that lecides the photosensitivity ofthe seed to red and far-red light. Thus it is deduced that theeffect of light is exerted primarily on the mechanical propertiesof the endosperm layer.
2. Neither red nor far-red light wasfound to affect the elongationof the radicle of de-coated seeds,whereas both powerfully affectthe germination of intact seeds.It follows that radicle elongationis not itself the limitingfactor in germination, although ofcourse it follows immediatelyupon the germination process proper.
3. In order to account forthe ability of red light to initiategermination, it is proposedthat the final step in the germinationcontrol process is theproduction of an enzyme whose actionenables the tip of theradicle to penetrate through the coat.This makes it possiblefor the radicle to begin elongating.Although the detectionof such an enzyme in the radicle wasnot successful, the cotyledonsdo produce both a pectinase andan enzyme hydrolyzing carboxymethylcellulose.Furthermore, seedsinjected with a cellulolytic, hemicellulolyticor pectolyticenzyme germinated to nearly the maximum extentin the dark.This gives considerable support to the hypothesis.

¹ Present address: Johnson Foundation for Medical Physics, Universityof Pennsylvania, Philadelphia, Pa., U. S. A. (Received December 5, 1962; )     

Metabolism of Pyrimidines in Protoplasts from Cultured Catharanthus roseus Cells

The metabolism of [2-¹⁴C]thymine, [2-¹⁴C]thymidine, [2-¹⁴C]uraciland [¹⁴C]uridine was investigated in protoplasts obtained fromsuspension cultures of Catharanthus roseus. Most of the exogenouslysupplied thymine, thymidine and uracil was degraded, and salvageof these pyrimidines accounted for 5–36 per cent of thetotal amount of ¹⁴C-labelled precursors which was metabolized.However, more than 80 per cent of the labelled uridine was utilizedfor the biosynthesis of nucleotides and nucleic acids, and therest was degraded. In contrast to the results from protoplastsof sugar cane cells in suspension culture, the data indicatethat protoplasts possess a pathway for the degradation of pyrimidines,and that the overall metabolism of these pyrimidines in protoplastsis very similar to the metabolism in the intact cells. Catharanthus roseus, madagascar periwinkle, protoplasts, pyrimidine metabolism     

CONASSIMINEA, A NEW GENUS OF THE ASSIMINEIDAE (CAENOGASTROPODA: RISSOOIDEA) FROM SOUTHEASTERN AUSTRALIA

A new genus of Assimineidae, Conassiminea, is described fromestuarine habitats in southeastern Australia (New South Wales,Tasmania and Victoria). Two new species, C. studderti and C.zheni, are included in the genus, the former being the typespecies. Conassiminea is distinct from all other assimineidgenera in two autapomorphies in the female reproductive system:the seminal receptacle has two ducts and the bursal duct isextremely wide. The phylogenetic relationships of the new genuswere examined using a morphological dataset. (Received 26 February 2005; accepted 22 April 2005)     

Comparison of genetic variation and differentiation using microsatellite markers among three rare threatened and one widespread toad lily species of Tricyrtis section Flavae (Convallariaceae) in Japan

Genetic diversities were examined using six microsatellite markers amplifiable in three rare and one widespread species of Tricyrtis section Flavae, which are endemic to Japan. Contrary to a general expectation, the three rare species, Tricyrtis flava, Tricyrtis ohsumiensis and Tricyrtis perfoliata, have comparable genetic variation at the species level to that of the widespread Tricyrtis nana. This is probably because T. nana has not sufficiently recovered genetic diversity from the bottleneck at speciation or because recent range contractions have occurred in the three rare species. Genetic diversity at the population level was smaller in the putative selfing species T. nana than in the other three outcrossing species. Compared with a preceding study using allozyme markers, the genetic diversity in microsatellite loci was considerably larger, probably resulting from higher mutation rates at the microsatellite loci. Owing to the high genetic diversity of the microsatellite markers, genetic differentiation among populations could be estimated even in T. nana with little allozyme polymorphism.     

Influence of Several Growth Regulators and Amino Acids on in vitro Organogenesis of Torenia fournieri Lind.

The effects of several growth regulators and amino acids onin vitro organogenesis of Torenia fournieri Lind. were determinedusing internodal segments. Treatment with 2,4-D¹ resulted innodular callus formation, while NAA and IAA induced roots constantlybut much less frequently shoot buds. Individually BA, zeatin,and 4-PU induced bud formation, but these shoot buds did notdevelop further. Formation of buds by cytokinin was influencedby a simultaneous application of NAA or 2,4-D, but not of IAA,its degree being reduced when BA was simultaneously appliedwith NAA or 2,4-D. When zeatin or kinetin was added with NAA,numerous roots were induced. The effects of various L-amino acids on in vitro organogenesiswere also investigated using the defined medium in which KNO₃was a principal source of nitrogen. The formation of buds wasconsiderably stimulated by alanine and asparagine, and slightlyby glutamic acid in the medium containing both NAA and BA, inwhich bud formation was easily induced. On the other hand, allamino acids except for glutamic acid and aspartic acid inhibitedroom formation in this medium. Root formation was greatly stimulated by proline, alanine, glutamine,glutamic acid, and aspartic acid, and slightly by arginine andtryptophan in the medium containing NAA but no BA. Glutamicacid and aspartic acid also enhanced bud formation in this medium.