Role of Contents of the Germinal Vesicle in Male Pronuclear Development and Cleavage of Starfish Oocytes

During 1-methyladenine induced germinal vesicle breakdown, contents of the germinal vesicle of starfish oocytes are mixed with the surrounding cytoplasm. Upon injection of contents of the germinal vesicle from immature (fully grown) oocytes into enucleated and inseminated oocytes, incorporated spermatozoa were not observed to change structurally. Alternatively, after treatment of the above oocytes with 1-methyladenine, sperm asters and male pronuclei were developed and subsequent cleavage was also detected. From these results, it is concluded that both action of 1-methyladenine and participation of contents of the germinal vesicle are indispensable for male pronuclear development and subsequent cleavage.     

Diet composition of the endangered giant water bug Lethocerus deyrolli (Hemiptera: Belostomatidae) in the rice fields of Japan: Which is the most important prey item among frogs,fish, and aquatic insects?

The food habits of the endangered giant water bug, Lethocerus deyrolli, were studied in the rice fields of Nose, in the north of Osaka Prefecture, Japan. Field observations revealed that frogs were the most important prey item. Frogs represented 86.4% and 78.6% in the diet of L. deyrolli in spring and summer, respectively. Among seven species of three families (Hylidae, Rhacophoridae, and Ranidae) exploited by L. deyrolli, the most important food item was adult Hyla japonica in spring and juvenile Rana nigromaculta in summer. Fish and aquatic arthropods were not considered important foods for L. deyrolli. The frog‐dependent food habits indicate that the recovery and conservation of frogs should be prioritized to protect L. deyrolli from extinction.     

CYTOLOGICAL AND CYTOCHEMICAL OBSERVATIONS ON THE EARLY STAGE OF INFECTION OF TOMATO HAIR CELLS BY TOBACCO MOSAIC VIRUS

Strips of epidermal tissue bearing hair cells were removed fromtomato stems. The lower surface exposed by the stripping wasinoculated with tobacco mosaic virus and the progress of infectionof the hair cells was followed microscopically and by extractionof infectivity. Shortly before infectivity could be extractedfrom the hair cells, the nuclei were observed to have migratedtowards the tran sverse wall of the basal hair cell nearestthe epidermis, apparently the site at which infection of thecell commences. After infection was apparent, the staining characteristicsof the nuclei, before and after RNase and DNase treatment, suggestedan accumulation of RNA. A granular body, different from X-bodiesmaintained a close association with the nucleus of TMV infectedhair cells, and was found to be rich in RNA, suggesting thatviral RNA of the nucleus may have been entering the cytoplasmvia the granular body. A possible mechanism of X-body formationarising from the granular body is suggested. ¹ Supported in part by a grant E-536 (C9) from the U. S. PublicHealth Service. ² Present address: Plant Pathology Laboratory, Faculty of Agriculture,Nagoya University, Anjo, Aichi (Japan). (Received March 4, 1963; )     

A stress‐inducible sulphotransferase sulphonates salicylic acid and confers pathogen resistance in Arabidopsis

Sulphonation of small molecules by cytosolic sulphotransferases in mammals is an important process in which endogenous molecules are modified for inactivation/activation of their biological effects. Plants possess large numbers of sulphotransferase genes, but their biological functions are largely unknown. Here, we present a functional analysis of the Arabidopsis sulphotransferase AtSOT12 (At2g03760). AtSOT12 gene expression is strongly induced by salt, and osmotic stress and hormone treatments. The T‐DNA knock‐out mutant sot12 exhibited hypersensitivity to NaCl and ABA in seed germination, and to salicylic acid (SA) in seedling growth. In vitro enzyme activity assay revealed that AtSOT12 sulphonates SA, and endogenous SA levels suggested that sulphonation of SA positively regulates SA production. Upon challenging with the pathogen Pseudomonas syringae, sot12 mutant and AtSOT12 over‐expressing lines accumulate less and more SA, respectively, when compared with wild type. Consistent with the changes in SA levels, the sot12 mutant was more susceptible, while AtSOT12 over‐expressing plants are more resistant to pathogen infection. Moreover, pathogen‐induced PR gene expression in systemic leaves was significantly enhanced in AtSOT12 over‐expressing plants. The role of sulphonation of SA in SA production, mobile signalling and acquired systemic resistance is discussed.     

Cytoplasmic Maturity Revealed by the Structural Changes in Incorporated Spermatozoon during the Course of Starfish Oocyte Maturation

Immature oocytes of the starfish, Asterina pectinifera, are polyspermic. Spermatozoa can enter immature oocytes upon insemination, but the changes associated with the fertilization process in oocytes matured with 1-methyladenine (1-MeAde), such as the formation of aster and pronucleus, were not observed. After immature oocytes, previously inseminated, were matured with 1-MeAde, the formation of the sperm monaster was observed during germinal vesicle breakdown (GVBD). Amphiasters and pronuclei were formed after the formation of the second polar body. The acquisition by oocytes of the capacity to undergo the normal process of fertilization, therefore, occurs during the course of oocyte maturation. After injection of the cytoplasm of maturing oocytes into inseminated immature oocytes, the formation of aster and pronucleus was observed, suggesting that maturation-promoting factor (MPF) may be involved in establishing the cytoplasmic conditions (cytoplasmic maturity) necessary for the fertilization process to occur. In contrast, when enucleated, inseminated halves of immature oocytes were treated with 1-MeAde, only monasters were formed, while in the nucleated halves both amphiasters and sperm pronuclei were formed. Thus, germinal vesicle material is required for the formation of amphiaster and sperm pronucleus but not for the formation of monaster. It is possible that the amount of MPF produced in enucleated halves was sufficient only for the formation of the monaster but not for the formation of the amphiaster and pronucleus, since it has been previously established that germinal vesicle material is necessary for the amplification of MPF. The formation of the monaster in the enucleated halves at a time corresponding to GVBD in nucleated controls suggests that the amount of MPF needed for this event is rather small. For the induction of subsequent fertilization process, large amounts of MPF may be required to establish the necessary cytoplasmic conditions, although other possible role of nuclear material is not excluded.     

SITE OF 1-METHYLADENINE RECEPTORS IN THE MATURATION OF STARFISH OOCYTES

Maturation of vitelline coat-free (VCF) oocytes of the starfish, Asterina pectinifera , was studied. When the oocytes, the vitelline coats of which were elevated by adding the ionophorc A-23187, were forced through two sheets of copper mesh, the vitelline coats were completely removed from the oocytes. Although some of the VCF oocytes underwent germinal vesicle breakdown following this mechanical treatment, most of them retained the normal germinal vesicles. These VCF immature oocytes underwent breakdown of germinal vesicles after addition of 1-methyladenine (1-MA). Dose-response curves of VCF oocytes to 1-MA were similar to those of normal oocytes. These results indicate that 1-MA reacts with the plasma membrane and that the presence of the vitelline coat is not prerequisite for inducing oocyte maturation.