Genetic analysis ofCochliobolus heterostrophus polyoxin-resistant mutants

Nine polyoxin-resistant mutants ofCochliobolus heterostrophus were isolated after ethyl methanesulphonate mutagenesis. All were highly resistant to polyoxin (MIC≥1,600 ppm). Crosses between the mutants and a wild-type strain revealed that the resistance trait was inherited to the offsprings in different fashions. Four of the mutant strains inherited polyoxin resistance in a 1∶1 segregation ratio, indicating that the phenotypes in these strains were due to alteration at a single locus. Allelism tests revealed four new loci,Pol1, Pol2, Pol3 andPol4, for polyoxin resistance in these mutant strains. The genes responsible for the phenotypes of the other five mutant strains were not determined, because of extremely slow growth of progenies in one cross, sterility in another cross, and inexplicable responses to polyoxin of the progenies in the other crosses. No linkage was detected between the genes for polyoxin resistance and mating type.     

Paleobiogeographical implications of inner bay Ostracoda during the Late Pleistocene Shimosueyoshi transgression,central Japan,with significance of its migration and disappearance in eastern Asia

A total of 79 ostracode species were recognized from the embayment sediments deposited during the Late Pleistocene Shimosueyoshi transgression in central Japan. The most dominant species was Neomonoceratina delicata, now abundant in tropical inner bays of the Ryukyu Islands, the South China Sea and southeastern Asia. Bicornucythere bisanensis, widely dominant species in enclosed middle muddy bays of temperate climatic zones in Japan and northern China, was also abundant in the middle and upper sequences. Most of the other main species were assigned to the “Japonic elements” and are presently common in tropical or subtropical and temperate shallow seas near the Japanese Islands. Four ostracode biofacies were identified using the Q-mode cluster analysis. A change in water depth was clearly revealed in the study sequence, based on the vertical changes in the biofacies and the relative abundances of fossil ostracode species. The single most dominant species, N. delicata, does not currently exist in the Japanese Islands north of the Tokara Strait (Watase's line: one of zoological lines of demarcation), in southern Japan. Based on a compilation of fossil and recent distribution records, it is believed that N. delicata migrated from the south of the Tokara Strait by the marine oxygen isotope stage (MIS) 11 (～ 430 ka), dominated other species in enclosed muddy bays and then spread to the northernmost areas during the MIS 5. However, almost all populations of this species probably disappeared north of the Tokara Strait during the Last Glacial Maximum due to a decrease in water temperature. This species could not survive colder water temperature and could not migrate north through the Tokara Strait during the postglacial transgression because the strait has been deep and wide since the Early Pleistocene. We conclude that this species lived commonly during the glacial stages of MIS 10, 8 and 6 north of the Tokara Strait because of the favorable water temperature for reproduction.     

Japanese Lifestyle during Childhood Prevents the Future Development of Obesity among Japanese-Americans

Objective

To evaluate whether a Japanese lifestyle during childhood could protect against the future development of obesity-associated metabolic diseases by comparing native Japanese with Japanese-Americans in whom genetic factors are the same.

Methods

Study subjects were 516 native Japanese and 781 Japanese-Americans who underwent medical examinations between 2007 and 2010. Japanese-Americans were divided into 444 first-generation immigrants (JA-1), who were born in Japan, and 337 second- or later-generation descendants (JA-2), who were born in the United States. The JA-2 group was then divided into the kibei subgroup (N = 79), who had moved to Japan before the age of 18 years and later returned to the United States, and the non-kibei subgroup (N = 258), who had never lived in Japan.

Results

The JA-2 group had the highest percentages of obesity, metabolic syndrome, and type 2 diabetes compared with native Japanese and JA-1. Furthermore, among JA-2, the prevalence of obesity and metabolic syndrome in the kibei subgroup was significantly lower than that in the non-kibei subgroup. The prevalence of diabetes in the kibei subgroup also tended to be lower than in the non-kibei subgroup.

Conclusions

The prevalence of obesity and metabolic diseases differed with residence in Japan during childhood among Japanese-Americans. These findings indicate the possibility that Japanese lifestyle during childhood could reduce the future risks for obesity-associated metabolic diseases.     

Male Isaza (Gymnogobius isaza, Gobiidae) prefer large mates: a counterstrategy against brood parasitism by conspecific females

Like many other gobies, male Isaza (Gymnogobius isaza) which are endemic to Lake Biwa, Japan, exclusively care for broods in nests. This goby may have an optimal range of brood size (i.e., an average clutch size of about 2000–3000 eggs) within which they may produce larger numbers of hatching young because much larger broods may be destroyed by fungal infection before hatching. This optimal brood size hypothesis (Takahashi et al. in J Ethol 22:153–159, 2004) predicts that (1) after spawning, both males and females will refuse additional spawning by other gravid females (second females) to keep brood sizes within optimal ranges, (2) larger fish will repel second females more successfully than will smaller fish, and thus, (3) both sexes prefer larger mates. To examine these predictions, we first observed Isaza’s aggressive behaviors in aquaria and investigated whether fish attacked and repelled second females that were introduced after spawning, and, if so, what were the sizes of fish that did so. Large fish, regardless of sex, aggressively prevented second females from entering the nest, but second females larger than the pairs displaced the pair females forcibly and spawned eggs into their clutches. Mate choice experiments showed that males preferred large females. Although females’ choice of large mates was not confirmed, many results may largely coincide with the predictions of the optimal brood size hypothesis. Thus, Isaza males’ choice of large mates will be advantageous for defending against brood parasitism by conspecific females and for achieving optimal clutch size.     

Characterizing the role of the microtubule binding protein Bim1 in Cryptococcus neoformans

During sexual development the human fungal pathogen Cryptococcus neoformans undergoes a developmental transition from yeast-form growth to filamentous growth. This transition requires cellular restructuring to form a filamentous dikaryon. Dikaryotic growth also requires tightly controlled nuclear migration to ensure faithful replication and dissemination of genetic material to spore progeny. Although the gross morphological changes that take place during dikaryotic growth are largely known, the molecular underpinnings that control this process are uncharacterized. Here we identify and characterize a C. neoformans homolog of the Saccharomyces cerevisiae BIM1 gene, and establish the importance of BIM1 for proper filamentous growth of C. neoformans. Deletion of BIM1 leads to truncated sexual development filaments, a severe defect in diploid formation, and a block in monokaryotic fruiting. Our findings lead to a model consistent with a critical role for BIM1 in both filament integrity and nuclear congression that is mediated through the microtubule cytoskeleton.     

Novel regulation of MHC class II function in B cells

The presence of post-translational regulation of MHC class II (MHC II) under physiological conditions has been demonstrated recently in dendritic cells (DCs) that potently function as antigen-presenting cells (APCs). Here, we report that MARCH-I, an E3 ubiquitin ligase, plays a pivotal role in the post-translational regulation of MHC II in B cells. MARCH-I expression was particularly high in B cells, and the forced expression of MARCH-I induced the ubiquitination of MHC II. In B cells from MARCH-I-deficient mice (MARCH-I KO), the half-life of surface MHC II was prolonged and the ubiquitinated form of MHC II completely disappeared. In addition, MARCH-I-deficient B cells highly expressed exogenous antigen-loaded MHC II on their surface and showed high ability to present exogenous antigens. These results suggest that the function of MHC II in B cells is regulated through ubiquitination by MARCH-I.     

Analysis of a nuclease activity of catalytic domain of Thermus thermophilus MutS2 by high-accuracy mass spectrometry

Electrospray ionization with Fourier-transform ion cyclotron resonance mass spectrometry (ESI–FT ICR MS) is a powerful tool for analyzing the precise structural features of biopolymers, including oligonucleotides. Here, we described the detailed characterization of a newly discovered nuclease activity of the C-terminal domain of Thermus thermophilus MutS2 (ttMutS2). Using this method, the length, nucleotide content and nature of the 5′- and 3′-termini of the product oligonucleotides were accurately identified. It is revealed that the C-terminal domain of ttMutS2 incised the phosphate backbone of oligodeoxynucleotides non-sequence-specifically at the 3′ side of the phosphates. The simultaneous identification of the innumerable fragments was achieved by the extremely high-accuracy of ESI–FT ICR MS.     

Physiological changes of premotor nonspiking interneurons in the central compensation of eyestalk posture following unilateral sensory ablation in crayfish

We investigated how the physiological characteristics and synaptic activities of nonspiking giant interneurons (NGIs), which integrate sensory inputs in the brain and send synaptic outputs to oculomotor neurons innervating eyestalk muscles, changed after unilateral ablation of the statocyst in order to clarify neuronal mechanisms underlying the central compensation process in crayfish. The input resistance and membrane time constant in recovered animals that restored the original symmetrical eyestalk posture 2 weeks after operation were significantly greater than those immediately after operation on the operated side whereas in non-recovered animals only the membrane time constant showed a significant increase. On the intact side, both recovered and non-recovered animals showed no difference. The frequency of synaptic activity showed a complex pattern of change on both sides depending on the polarity of the synaptic potential. The synaptic activity returned to the bilaterally symmetrical level in recovered animals while bilateral asymmetry remained in non-recovered ones. These results suggest that the central compensation of eyestalk posture following unilateral impairment of the statocyst is subserved by not only changes in the physiological characteristics of the NGI membrane but also the activity of neuronal circuits presynaptic to NGIs.