Reproductive biology of the female Japanese mantis shrimp Oratosquilla oratoria (Stomatopoda) in relation to changes in the seasonal pattern of larval occurrence in Tokyo Bay, Japan

ABSTRACT:   The reproductive traits and the monthly larval abundance of the mantis shrimp Oratosquilla oratoria were investigated in Tokyo Bay, Japan, in 2002. The goal of the study was to elucidate the cause of changes in the monthly pattern of larval abundance from the 1980s to the 1990s as these changes relate to variation in the stock size of the adult shrimp. Oogenesis was divided into 10 stages by histological observation. The developmental stage of oocytes in an individual's ovary was synchronous, suggesting that almost all the oocytes in an ovary are spawned at the same time. The size at first maturity was estimated to be 7 ≤ body length ( BL ) < 8 cm. Fecundity was expressed as a function of BL , ranging from 19 300 eggs for 8 cm BL to 92 100 eggs for 14 cm BL . Small female shrimps (<10 cm BL ) spawned around August. Most large female shrimps (≥10 cm BL ) spawned around May, and some large female shrimps also spawned until September. Although most large female shrimps spawned in spring, the larval abundance was low before July and high from August onwards. The results suggest that a substantial decrease in the stock size of large individuals causes the low larval abundance before July.     

Detoxification of α-tomatine by tomato pathogens Alternaria alternata tomato pathotype and Corynespora cassiicola and its role in infection

In tomato plants, α-tomatine, a steroidal glycoalkaloid saponin, inhibits fungal growth. Tomato pathogens that produce host-specific toxins, Alternaria alternata tomato pathotype causing Alternaria stem canker and Corynespora cassiicola causing Corynespora target spot, were investigated for sensitivity to α-tomatine. Although spore germination of A. alternata pathogenic and nonpathogenic to tomato and of C. cassiicola pathogenic to tomato was not affected by 0.1 mM α-tomatine, spore germination of C. cassiicola nonpathogenic to tomato was significantly inhibited. This result showed that A. alternata, regardless of its pathogenicity, and only the C. cassiicola pathogenic to tomato are resistant to α-tomatine. Germinating spores of A. alternata and C. cassiicola resistant to α-tomatine detoxified α-tomatine by degrading it to a less polar product. After inoculation of tomato leaves, spores of A. alternata and C. cassiicola nonpathogenic to tomato germinated and formed appressoria, but did not form infection hyphae in host tissues. When a host-specific toxin (CCT-toxin) produced by C. cassiicola pathogenic to tomato was added to nonpathogenic spores, colonization within leaves was observed in A. alternata, but not in C. cassiicola. On the other hand, when spores of C. cassiicola nonpathogenic to tomato were suspended in spore germination fluid of nonpathogenic A. alternata with α-tomatine detoxification activity, the fungus could be induced to colonize leaves in the presence of CCT-toxin. These results indicate that A. alternata tomato pathotype and C. cassiicola pathogenic to tomato detoxify α-tomatine during infection and that this detoxification is essential for host colonization by pathogens that produce host-specific toxins.     

Pathological evaluation of host-specific AAL-toxins and fumonisin mycotoxins produced by Alternaria and Fusarium species

Host-specific AAL-toxins and mycotoxin fumonisins are structurally related and were originally isolated from the tomato pathotype of Alternaria alternata and from Fusarium verticillioides, respectively. Previous reports on the production of fumonisin derivatives by the tomato pathotype suggested a possible involvement in the pathogenicity of the pathogen. Here, we have evaluated the role of fumonisin in A. alternata–tomato interactions. The results indicate that highly pathogenic isolates of A. alternata tomato pathotype produce AAL-toxin as the sole toxin, strongly implicating it as a pathogenicity factor. The related compound, fumonisin, is also toxigenic and has infection-inducing activity on susceptible tomato plants.     

Ectomycorrhizal fungal communities of Dipterocarpus alatus seedlings introduced by soil inocula from a natural forest and a plantation

We attempted to introduce ectomycorrhizal (ECM) fungi onto seedlings of Dipterocarpus alatus (Dipterocarpaceae) by soil inocula collected from tree stands of D. alatus. Top soils collected from beneath the trees of D. alatus in a dry evergreen forest and a 15-year-old plantation were inoculated onto germinating seeds of D. alatus. After 7 months of seedling cultivation, ECM fungal communities in the seedlings were investigated based on the sequences of ITS rDNA. The ECM fungi detected were divided into 19 phylotypes by molecular analysis. Most of the phylotypes were identified as ECM fungal taxa, i.e., Clavulina, Laccaria, Lactarius, Tomentella, Pyronemataceae, and Tricholomataceae. Accordingly, we can confirm that soil inoculation is a simple method to induce ECM formation with diverse fungi in pot cultured seedlings, which would be useful for introducing diverse ECM fungi to dipterocarp plantations.     

Serological relationships among five strains of infectious pancreatic necrosis virus

Abstract. The serological relationships of five strains of infectious pancreatic necrosis virus (IPNV) were examined by cross-neutralization, cross-fluorescent antibody (FA) and cross-immunodiffusion (ID) tests. Few serological relationships among these strains were observed by the cross-neutralization test, which is consistent with previous studies. Some cross reactions were observed by the FA test when antisera were reacted with cells infected with heterologous strains of IPNV. However, close antigenic relationships were demonstrated among these strains of IPNV by using the ID test when antisera to each strain of IPNV were titrated with their respective or heterologous antigens. The results of the present study showed that substantial antigenic relationships exist among the strains of IPNV examined. It is suggested that strain specific antigens which can be detected by virus neutralization and FA tests might exist on the surface of the virion. The FA test proved to be a useful method for detecting viral antigens of several strains of IPNV in tissue culture cells since monovalent antiserum reacted with homologous and heterologous IPNV antigens.     

Chemerin fragments show different effects on systemic blood pressure dependent on carboxyl-terminal cleavage site

Chemerin is an adipocytokine whose concentration in blood correlates positively with blood pressure (BP). We have recently revealed that acute intracerebroventricular (i.c.v.) injection of chemerin-9, an active fragment of human chemerin, increased systemic BP in normal Wistar rats, suggesting that chemerin is involved in the central nervous control of peripheral BP. After secreted as an inactive form as prochemerin, a mature form of active chemerin is produced through the cleavage of its carboxyl (C)-terminus by proteases. Although the activity of cleaved products of chemerin has been examined in vitro, in vivo effects remained to be elusive. In order to explore them, we performed acute i.c.v. injection of mouse chemerin-9 (mChemerin-9; 148F-156S), mouse chemerin-8 (mChemerin-8; 148F-155F), and mouse chemerin-7 (mChemerin-7; 148F-154A) into Wistar rats, and examined the effects on systemic BP. After chemerin fragment (1–30 nmol/head, i.c.v.) was cumulatively administered, systemic BP was measured by a cannulation method under an isoflurane anesthesia. mChemerin-9 but not mChemerin-8 and -7 induced a pressor response, which was concentration-dependent. In conclusion, we for the first time demonstrated that mChemerin-9 that corresponds to the C-terminal nine amino acids of active mouse chemerin156S increased systemic BP in rats, and also that chemerin fragments showed different effects on systemic BP dependent on how their C-terminus was cleaved.     

The presence of double-stranded RNAs in <Emphasis Type="Italic">Alternaria alternata</Emphasis> Japanese pear pathotype is associated with morphological changes

Strains of the Japanese pear pathotype of Alternaria alternata were screened for double-stranded RNAs (dsRNAs). Four strains had several dsRNAs; strain N18 was associated with several dsRNAs and had impaired growth phenotypes such as irregular mycelium and abnormal pigmentation. We isolated dsRNA-cured isolates from strain N18 by single-conidium isolation. The dsRNA-cured isolates had recovered normal growth and pigmentation. Enlarged vesicles were observed in mycelial cells of the original dsRNA-carrying N18 strain. DAPI nuclear staining revealed regression of the nuclei in dsRNA-carrying N18 cells. These results indicate that the dsRNAs might have negative effects, such as apoptosis-like cell death, on the host fungus.     

Identification of putative defense-related genes in Japanese pear against <Emphasis Type="Italic">Alternaria alternata</Emphasis> infection using suppression subtractive hybridization and expression analysis

The Japanese pear pathotype of Alternaria alternata, a toxin-dependent necrotrophic pathogen, causes black spot of Japanese pear by producing the host-specific AK-toxin. Pre-inoculation with nonpathogenic A. alternata or pretreatment with an elicitor prepared from A. alternata reduced disease symptoms caused by the pathogen. Salicylic acid- and jasmonic acid-dependent signaling pathways are not involved in the induced resistance to infection by the pathogen. The expression of multiple defense-related genes in Japanese pear leaves inoculated with nonpathogenic A. alternata was examined using suppression subtractive hybridization. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank database as accessions DC993229–DC993535.     

Induced resistance in tomato plants to the toxin-dependent necrotrophic pathogen Alternaria alternata

A necrotrophic pathogen, the tomato pathotype of Alternaria alternata (Aa) causes Alternaria stem canker on tomato. Its pathogenicity depends on the production of host-specific AAL-toxin. Pre-inoculation with nonpathogenic Aa or pretreatment an elicitor prepared from Aa reduced disease symptoms by the pathogen. Salicylic acid (SA)- and jasmonic acid (JA)-dependent defense responses in tomato are not involved in the resistance to the pathogen induced by nonpathogenic Aa. The results suggest that an alternative and unknown signaling pathway independent of SA- and JA-signaling might modulate the induced resistance by activating the expression of the multiple defense genes.     

<Emphasis Type="Italic">Alternaria alternata</Emphasis> apple pathotype (<Emphasis Type="Italic">A. mali</Emphasis>) causes black spot of European pear

A disease caused by Alternaria alternata occurred on the leaves of European pear cultivar Le Lectier in Niigata Prefecture, Japan, and was named black spot of European pear. In conidial inoculation tests, the causal pathogen induced not only small black lesions on the leaves of European pear cultivar Le Lectier, but severe lesions on the leaves of apple cultivar Red Gold, which is susceptible to the A. alternata apple pathotype (previously called A. mali) causing Alternaria blotch of apple. Interestingly, the apple pathotype isolate showed the same pathogenicity as the European pear pathogen. HPLC analysis of the culture filtrates revealed that A. alternata causing black spot of European pear produced AM-toxin I, known as a host-specific toxin of the A. alternata apple pathotype. AM-toxin I induced veinal necrosis on leaves of Le Lectier and General Leclerc cultivars, both susceptible to the European pear pathogen, at 5?×?10^?7 M and 10^?6 M respectively, but did not affect leaves of resistant cultivars at 10^?4 M. PCR analysis with primers that specifically amplify the AM-toxin synthetase gene detected the product of expected size in the pathogen. These results indicate that A. alternata causing black spot of European pear is identical to that causing Alternaria blotch of apple. This is the first report of European pear disease caused by the A. alternata apple pathotype. This study provides a multiplex PCR protocol, which could serve as a useful tool, for the epidemiological survey of these two diseases in European pear and apple orchards.