Regulatory role of polyamine in the acid phosphatase from potato tubers.

Effects of polyamine and metal ions on the new type of acid phosphatase purified from potato (Solanum tuberosum L. Irish Cobbler) tubers were analyzed. The enzyme belongs to nonspecific acid phosphatase family (EC 3.1.3.2), which hydrolyzes various phosphorylated substrates. The enzyme hydrolyzed inorganic pyrophosphate as a preferred substrate, and exhibited the hyperbolic kinetics with respect to the substrate, inorganic pyrophosphate in the absence of metal cations. Polyamine activated the enzyme effectively by lowering the K(m) value without appreciable changes in the maximal velocity. The most effective polyamines as activators were spermine and spermidine. Mg(2+) ion increased the K(m) value without affecting the maximal velocity of the enzyme, but Ca(2+) ion decreased both the K(m) and V(max) values. Increasing concentrations of spermine also decreased the K(m) value irrespective of Mg(2+) ion included, but gave a constant K(m) and V(max) values in the absence and presence of Ca(2+) ion. Action of spermine and metal ions can be explained by the complex formation with the substrate pyrophosphate. The acid phosphatase from potato can utilize the pyrophosphate-spermine or pyrophosphate-Ca(2+) complex as the preferred substrates. However, the enzyme can use the pyrophosphate-Mg complex with a weak affinity for the active site. Polyamine activates acid phosphatase in the absence and presence of metal cations, and activation by polyamine of the enzyme may contribute to the stimulation of starch biosynthesis and the control of glycolysis/gluconeogenesis by regulating PPi levels in growing potato tubers.     

Coloration and ontogenetic features of fluviatile species of <Emphasis Type="Italic">Rhinogobius</Emphasis> (Gobioidei: Gobiidae) in Amami-oshima Island,Ryukyu Islands,Japan

 The fluviatile Rhinogobius sp. 1 (hereinafter R. sp. 1) (Japanese name kibara-yoshinobori or English name yellow belly medium-egg type) is broadly distributed in the Ryukyu Islands ranging from Amami-oshima Island to Iriomote Island. However, based on the molecular evidence, this species has probably had multiple origins from amphidromous species. We compared the coloration of specimens at Amami-oshima I. with that of the other specimens (islands) in the Ryukyu Is. Amami-oshima I. specimens of R. sp. 1 were different from the specimens of other populations in having five to six cross lines on the caudal fin. We examined the early life history of fluviatile Rhinogobius at Amami-oshima I., based on rearing experiments, and estimated the age of wild specimens by counting otolith increments. Spawned egg capsules of “Rhinogobius sp. 1” at Amami-oshima I. were larger than those of amphidromous species. Their developmental stage in newly hatched larvae was similar to that of Okinawan R. sp. 1 in having a straight notochord; however, it had a flexed notochord earlier than that of Rhinogobius sp. 2 (hereinafter R. sp. 2) (aobara-yoshinobori or blue belly medium-egg type). The ontogenetic trajectory of “Rhinogobius sp. 1” in Amami-oshima I. was similar to Okinawan R. sp. 1 (30 days in larval duration) but different from R. sp. 2 (15 days). In amphidromous relatives of R. sp. 2, developmental timing during larval period was earlier than in the amphidromous relatives of R. sp. 1. It has been suggested that the phenomenon of fluvial landlocking has been accompanied somewhat by egg size increase (on the basis of a few examples). However, the ontogenetic trajectories of fluviatile Rhinogobius species may be a reflection of those of ancestral amphidromous species. Received: March 18, 2002 / Revised: November 7, 2002 / Accepted: December 10, 2002     

Components of male fitness in relation to body size in Epirrita autumnata (Lepidoptera, Geometridae)

Abstract. 1. The effect of body size on different components of male fitness was studied for Epirrita autumnata , a geometrid known for its eruptive population dynamics. Body size is the main determinant of female fecundity in this species.
2. Longevity of males was found to have a weak negative correlation with body size at low temperatures. No significant correlation was found at higher temperatures.
3. We found no correlation between male size and female fecundity or egg size which is consistent with the small size of spermatophores in this species.
4. Small and large males were equally successful when allowed to compete for females in laboratory conditions.
5. In one or two field collections, males found mating were larger than males found singly. Large males also had an advantage in finding of virgin females, offered experimentally. No size-assortative mating was recorded.
6. We conclude that size-dependent mate location ability is the factor accounting for most of the variance in male fitness in E.autumnata. The dependence of fitness on body size may well be equally strong in males and females.     

The Dictyostelium developmental cDNA project: generation and analysis of expressed sequence tags from the first-finger stage of development.

In an effort to identify and characterize genes expressed during multicellular development ill Dictyostelium, we have undertaken a cDNA sequencing project. Using size-fractionated subsets of cDNA from the first finger stage, two sets of gridded libraries were constructed for cDNA sequencing. One, library S, consisting of 9984 clones, carries relatively short inserts, and the other, library L, which consists of 8448 clones, has longer inserts. We sequenced all the selected clones in library S from their 3'-ends, and this generated 3093 non-redundant, expressed sequence tags (ESTs). Among them, 246 ESTs hit known Dictyostelium genes and 910 showed significant similarity to genes of Dictyostelium and other organisms. For library L, 1132 clones were randomly sequenced and 471 non-redundant ESTs were obtained. In combination, the ESTs from the two libraries represent approximately 40% of genes expressed in late development, assuming that the non-redundant ESTs correspond to independent genes. They will provide a useful resource for investigating the genetic networks that regulate multicellular development of this organism.     

Consequences of defoliation on phenological interaction between Epirrita autumnata and its host plant, Mountain Birch

1. Defoliation-induced changes in the budbreak phenology of Mountain Birches ( Betula pubescens ssp. tortuosa (Ledeb.) Nyman), and their effects on herbivore performance, were investigated during an outbreak of the spring-feeding geometrid, Epirrita autumnata (Bkh.).
2. Total defoliation (followed by refoliation) by E. autumnata larvae was required to achieve significant delaying of budbreak of Mountain Birch one year after damage.
3. Delayed budbreak has potentially deleterious effects on herbivore performance. However, E. autumnata larvae show phenotypic responses that increase the synchrony between larvae and leaves: high larval density, a prerequisite for severe defoliation, delays egg hatch in the following year.
4. Late hatching larvae performed as well on birches with delayed budbreak due to the previous year's total defoliation as did early hatching larvae on birches with earlier budbreak.