Changes in Targeting Efficiencies of Proteins to Plant Microbodies Caused by Amino Acid Substitutions in the Carboxy-terminal Tripeptide

It has been demonstrated that the carboxyl terminus of microbodyenzymes functions as a targeting signal to microbodies in higherplants. We have examined an ability of 24 carboxy-terminal aminoacid sequences to facilitate the transport of a cytosolic passengerprotein, ß-glucuroni-dase, into microbodies in greencotyledonary cells of trans-genic Arabidopsis. Immunoelectronmicroscopic analysis revealed that carboxy-terminal tripeptidesequences of the form [C/A/S/P]-[K/R]-[I/L/M] function as amicrobody-targeting signal, although tripeptides with prolineat the first amino acid position and isoleucine at the carboxylterminus show weak targeting efficiencies. All known micro-bodyenzymes that are synthesized in a form similar in size to themature molecule, except catalase, contain one of these tripeptidesequences at their carboxyl terminus. (Received April 14, 1997; Accepted April 8, 1997)     

Economical Speed and Energetically Optimal Transition Speed Evaluated by Gross and Net Oxygen Cost of Transport at Different Gradients

The oxygen cost of transport per unit distance (CoT; mL·kg^-1·km^-1) shows a U-shaped curve as a function of walking speed (v), which includes a particular walking speed minimizing the CoT, so called economical speed (ES). The CoT-v relationship in running is approximately linear. These distinctive walking and running CoT-v relationships give an intersection between U-shaped and linear CoT relationships, termed the energetically optimal transition speed (EOTS). This study investigated the effects of subtracting the standing oxygen cost for calculating the CoT and its relevant effects on the ES and EOTS at the level and gradient slopes (±5%) in eleven male trained athletes. The percent effects of subtracting the standing oxygen cost (4.8 ± 0.4 mL·kg^-1·min^-1) on the CoT were significantly greater as the walking speed was slower, but it was not significant at faster running speeds over 9.4 km·h^-1. The percent effect was significantly dependent on the gradient (downhill > level > uphill, P < 0.001). The net ES (level 4.09 ± 0.31, uphill 4.22 ± 0.37, and downhill 4.16 ± 0.44 km·h^-1) was approximately 20% slower than the gross ES (level 5.15 ± 0.18, uphill 5.27 ± 0.20, and downhill 5.37 ± 0.22 km·h^-1, P < 0.001). Both net and gross ES were not significantly dependent on the gradient. In contrast, the gross EOTS was slower than the net EOTS at the level (7.49 ± 0.32 vs. 7.63 ± 0.36 km·h^-1, P = 0.003) and downhill gradients (7.78 ± 0.33 vs. 8.01 ± 0.41 km·h^-1, P < 0.001), but not at the uphill gradient (7.55 ± 0.37 vs. 7.63 ± 0.51 km·h^-1, P = 0.080). Note that those percent differences were less than 2.9%. Given these results, a subtraction of the standing oxygen cost should be carefully considered depending on the purpose of each study.     

Purification of Protein Body-I of Rice Seed and its Polypeptide Composition

Protein body type one (PB-I) was isolated and purified fromdeveloping rice grain by a combination of sucrose density gradientcentrifugation and treatment with pepsin. SDS-PAGE analysisshowed that isolated PB-I contains several polypeptide groups,the largest having an apparent molecular size of 13 kDa andtwo smaller ones of 10 kDa and 16 kDa. The 13-kDa group wasfound to be composed of two polypeptides of slightly differentmolecular sizes, 13a (larger component) and 13b (smaller component).Most of the 13a and 13b polypeptides were shown to be largelyprolamins, although there were also some salt- and alcohol-insolublepolypeptides with an apparent molecular size of 13 kDa. It wasconcluded that PB-I is the accumulation site of rice prolamin.It was further estimated that the protein amount in PB-I accountedfor about 20% of the total protein of rice endosperm. (Received March 20, 1987; Accepted September 8, 1987)     

Three species of Trebius Krøyer, 1838 (Copepoda: Siphonostomatoida) parasitic on Pacific elasmobranchs

The paratypes of Trebius akajeii Shiino, 1954, originally collected from Dasyatis akajei (Müller & Henle) at Owase, Japan, and the paratypes and newly collected specimens of T. latifurcatus Wilson, 1921, previously collected from Urolophus and Myliobatis at Venice, California, are redescribed. New host records for T. latifurcatus are: Torpedo californica Ayres, Squatina californica Ayres, Rhinobatos productus (Ayres), Platyrhinoides triseriata (Jordan & Gilbert), Raja inornata (Jordan & Gilbert) and Gymnura marmorata (Cooper). A new species, Trebius heterodonti, is described from the horn shark Heterodontus francisci (Girard) collected from southern California waters. These three species of Trebius are apparently closely related to each other. Diagnostic characters of the species are provided along with a discussion on the taxonomic value of selected features.     

Diploid and triploid offspring of triploid agamosporous fernDryopteris pacifica

A cytological and reproductive study of the diploid and triploid agamosporousDryopteris pacifica was made to elucidate the origin of its infraspecific cytotypes. Some triploids produced 16 spore mother cells (SMCs) sometimes with n=41II+41I chromosomes, in addition to eight SMCs with n=123II, in each sporangium. In the former case the 16 SMCs usually underwent abnormal meiosis to give rise to some 50 spores, some of which were regular-shaped; in the latter the eight SMCs multiplied into 32 spores by normal meiosis. We found that spores from one of the triploid plants developed into either diploid or triploid gametophytes, which further apogamously produced diploid or triploid sporophytes, respectively. This novel mechanism of ploidy reduction is discussed in relation to the origin of diploid agamosporous ferns, the taxonomic complexity of the species, and the correlation of agamospory with polyploidy. The mechanism is also compared to that operating in agamospermous angiosperms.     

A physical characterization of biological information and communication system model of ecosystems

What is information for living organisms? An answer to this question is given on a physical basis and a contrast between genetic information and sensory information is stressed with a relation to information theory. A simple model of an environment of living organisms is investigated on the basis of communication systems model proposed by the author and a cost of information transmission is taken into consideration through capacity cost theory. It is shown that channel capacity of information theory can be interpreted as an environment, and furthermore that a large diversity of genetic messages needs a large capacity of the environment. In addition, a definition of life in terms of information is proposed and a unified view on life processes is suggested.     

The mating system ofTokunagayusurika akamusi (Diptera; Chironomidae): II. Experimental analysis of male mating behaviour at the resting place

Mating behaviour ofTokunagayusurika akamusi searching at the resting place (lakeside vegetation, although mating also occurs in the air by swarming) was investigated at the shore of Lake Biwa. Coinciding with the arrival of newly emerged adults, previously emerged males walked about to search for mates at the resting place. When a searching male came into contact with a fresh (newly emerged) individual, he attempted to copulate with it regardless of its sex. Consequently, males copulated with fresh females, which were more likely to be virgin at the resting place, suggesting that the first male might contribute best to the fertilization.