Experimental assessment of the fecundity of Eucypris virens (Ostracoda, Crustacea) under natural sex ratios

1. The adaptive significance of the observed variations in sex ratios in non‐marine ostracods is unclear. This study quantified the fecundity of females taken from a presumed fully sexual Eucypris virens population that were experimentally combined with different proportions of males (male : female sex ratios: 1 : 1, 1 : 2, 1 : 4, 1 : 8 and 0 : 1). 2. The results yielded no indications that female fecundity is altered by short‐term variations in the proportion of males, at least not within the range of sex ratios that are common in natural ostracod populations. Complete removal of males, however, did strongly reduce hatching success of dried eggs. This suggests the need for multiple mating events during the reproductive lifetime of the female. It also emphasizes the need for a minimum number of males, although this minimum number evidently may be rather low, as we found a high number of spermatozoa in the seminal receptacles after a single mating event. 3. The sex ratio in the source population was strongly female biased (1 : 3.4; n = 514), whereas in the hatchling assemblages reared in the laboratory, males and females were found in equal proportions (1 : 1.0; n = 1516), irrespective of the prevailing sex ratio. This clear discrepancy is intriguing, and points to the importance of epigenetic factors for the determination of field sex ratios.     

Antagonistic potential of Gliocladium virens and Trichoderma longibrachiatum to phytopathogenic fungi

Three isolates of Gliocladium virens (G1, G2 and G3) and two of Trichoderma longibrachiatum (T1 and T2) were screened against isolates of three soilborne plant pathogens namely Rhizoctonia solani, Sclerotium rolfsii and Pythium aphanidermatum. G. virens exhibited stronger hyperparasitism and wider biological spectrum than T. longibrachiatum. Further, similarities as well as variation was observed in the ability of the various isolates to invade the test pathogens in dual culture. For the hyperparasites, acidic pH range (5.0 to 5.5) favoured both growth and spore germination. The hyperparasites made direct contact with the pathogens followed by varied modes of attack invariably leading to cell disruption. Antagonists, G1 and G3 revealed strong antibiosis while T2 showed moderate effect. All the isolates produced enhanced levels of lytic enzymes adaptively and there were marked differences among them. However, no correlation was observed between these attributes and the hyperparasitic potential of the various isolates in dual culture. The relevance and the role of enzymes and toxic metabolite(s) in the antagonism of G. virens and T. longibrachiatum to these pathogens are discussed.     

Morphogenesis in the Heterotrich Ciliate Climacostomum virens. I. Oral Development During Cell Division

The principal characteristics of stomatogenesis during division in Climacostomum virens are: (A) Kinetosomal proliferation on the left side of a variable number of kineties in the ventral somatic cortex forms an oral primordium consisting of several kinetosomal fields, which then fuse to form a single anarchic field. (B) A constant topographical relationship exists between the primordium and a well defined cortical pattern, the zone of discontinuity. (C) The anarchic field primordium divides into 2 unequal parts—to the left, the AZM primordium, and to the right, the paroral primordium, which differentiates into the apical membranelles, the peristomial field, and the buccal tube. (D) Preoral and oblique kineties of the somatic cortex form along the right side of the paroral primordium. (E) Parental oral structures are partially dedifferentiated. Stomatogenesis in C. virens and other heterotrichs is compared.     

Light and Electron Microscopic Observations on the Heterotrich Ciliate Climacostomum virens

SYNOPSIS. Alveolar membranes and an epiplasm exist under the cell membrane of the noncontractile heterotrich ciliate Climacostomum virens. Postciliary microtubular ribbons join at the right of each somatic kinety to form a Km fiber. Two transverse microtubular fibers occur per kinetosomal pair. A myonemal network interconnects the kinetosomal bases intrakinetally and interkinetally. Ultrastructural comparisons are made between the contractile and noncontractile heterotrichs.
The buccal cortex consists of an adoral zone of membranelles, a peristomal field, a buccal tube, the apical membranelles, and a haplokinety. The kineties of the peristomal field and buccal tube are rows of paired kinetosomes, with a postciliary ribbon of microtubules arising from the posterior kinetosome of each pair, and a transverse ribbon and an oblique ribbon from the anterior kinetosome. No Km fibers exist in this region. The haplokinety is a collar of paired kinetosomes surrounding the cytostome; a postciliary microtubular ribbon descends from each kinetosomal pair into the cytostomal region. Ultrastructural details of the buccal cortex of C. virens and other heterotrichs are compared. The nemadesmata which lie under the membranelles are implicated in the body bending of C. virens.
Algae endosymbiotic in the cytoplasm of C. virens are described.     

The essential effector SCRE1 in Ustilaginoidea virens suppresses rice immunity via a small peptide region

The biotrophic fungal pathogen Ustilaginoidea virens causes rice false smut, a newly emerging plant disease that has become epidemic worldwide in recent years. The U. virens genome encodes many putative effector proteins that, based on the study of other pathosystems, could play an essential role in fungal virulence. However, few studies have been reported on virulence functions of individual U. virens effectors. Here, we report our identification and characterization of the secreted cysteine-rich protein SCRE1, which is an essential virulence effector in U. virens. When SCRE1 was heterologously expressed in Magnaporthe oryzae, the protein was secreted and translocated into plant cells during infection. SCRE1 suppresses the immunity-associated hypersensitive response in the nonhost plant Nicotiana benthamiana. Induced expression of SCRE1 in rice also inhibits pattern-triggered immunity and enhances disease susceptibility to rice bacterial and fungal pathogens. The immunosuppressive activity is localized to a small peptide region that contains an important ‘cysteine-proline-alanine-arginine-serine’ motif. Furthermore, the scre1 knockout mutant generated using the CRISPR/Cas9 system is attenuated in U. virens virulence to rice, which is greatly complemented by the full-length SCRE1 gene. Collectively, this study indicates that the effector SCRE1 is able to inhibit host immunity and is required for full virulence of U. virens.     

Effect of opportunistic fungi on the life cycle of the root-knot nematode ( Meloidogyne javanica) on brinjal

The effect of four opportunistic fungi viz., Paecilomyces lilacinus, Cladosporium oxysporum, Gliocladium virens and Talaromyces flavus on the life cycle of the root-knot nematode, Meloidogyne javanica, on brinjal was evaluated under glasshouse conditions. The results revealed that these fungi affected the penetration and development of M. javanica. The life cycle of M. javanica was delayed by 10, 7, 4 and 2 days in the presence of P. lilacinus, C. oxysporum, G. virens and T. flavus respectively. Fecundity, number of eggs per eggmass and number of larvae was also reduced in the presence of these opportunistic fungi. However, the number of males increased in the presence of opportunistic fungi.     

Studies on the transmission of some Fusarium spp. to potato progeny tubers from mother plants and its biological control

Fusarium spp. attack potato roots causing root-rot, damping-off and wilt disease in Assuit Governorate. Forty-five Fusarium isolates were isolated from F. nygamai, F. acutatum, F. solani, F. proliferatum, F. subglutinans, and F. oxysporum. Isolates were tested for their pathogenic capability on Burn potato variety during growing season 2007/2008. Isolates infect potato plants causing either damping-off or wilt symptoms. Isolates varied in their virulence. Role of potato tuber seed in the transmission of the causal pathogen to daughter using Electrophoresis. Protein profiles of the tested isolates divided into four sub-clusters at similarity levels 93.79, 91.55 and 92.62% while isolate of Fusarium profile No. 11 formed separate sub-clusters at similarity level 69.79%. F. nygamai and F. solani were notable exception because profile No. 4 of F. nygamai from roots and profile No. 4 from sprouts were almost identical (similarity level 96.81%); similarity level between profile No. 8 from roots and profile no/8 from sprouts was 95.44%. Results prove that F. nygamai and F. solani are potato tuber seed-borne fungus. T. harzianum, T. viride, T. longibrachiatum, G. virens and E. nigrum or its filtrate inhibited the growth of F. nygamai, F. acutatum, F. solani, F. proliferatum, F. subglutinans and F. oxysporum. The formulation of T. harzianum, T. longibrachiatum and G. virens against tested pathogenic fungi reduce disease incidence under greenhouse conditions.     

Enhanced fungal resistance in transgenic cotton expressing an endochitinase gene from Trichoderma virens

Mycoparasitic fungi are proving to be rich sources of antifungal genes that can be utilized to genetically engineer important crops for resistance against fungal pathogens. We have transformed cotton and tobacco plants with a cDNA clone encoding a 42 kDa endochitinase from the mycoparasitic fungus, Trichoderma virens. Plants from 82 independently transformed callus lines of cotton were regenerated and analysed for transgene expression. Several primary transformants were identified with endochitinase activities that were significantly higher than the control values. Transgene integration and expression was confirmed by Southern and Northern blot analyses, respectively. The transgenic endochitinase activities were examined in the leaves of transgenic tobacco as well as in the leaves, roots, hypocotyls and seeds of transgenic cotton. Transgenic plants with elevated endochitinase activities also showed the expected 42 kDa endochitinase band in fluorescence, gel-based assays performed with the leaf extracts in both species. Homozygous T2 plants of the high endochitinase-expressing cotton lines were tested for disease resistance against a soil-borne pathogen, Rhizoctonia solani and a foliar pathogen, Alternaria alternata. Transgenic cotton plants showed significant resistance to both pathogens.