Identification of a novel domain shared by putative components of the endocytic and cytoskeletal machinery.
We have identified a approximately 140 amino acid domain that is shared by a variety of proteins in budding and fission yeast, nematode, rat, mouse, frog, oat, and man. Typically, this domain is located within 20 residues of the N-terminus of the various proteins. The percent identity among the domains in the 12 proteins ranges from 42 to 93%, with 16 absolutely conserved residues: N-x(11-13)-V-x2-A-T-x(34-36)-R-x(7-8)-W-R-x3-K-x12-G-x-E-x15 -L-x11-12-D-x-G-R-x11-D-x7-R. Even though these proteins share little beyond their segment of homology, data are emerging that several of the proteins are involved in endocytosis and or regulation of cytoskeletal organization. We have named this protein segment the ENTH domain, for Epsin N-terminal Homology domain, and hypothesize that it is a candidate for binding specific ligands and/or enzymatic activity in the cell. (+info)
Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi.
In the past, molecular clocks have been used to estimate divergence times among animal phyla, but those time estimates have varied widely (1200-670 million years ago, Ma). In order to obtain time estimates that are more robust, we have analysed a larger number of genes for divergences among three well-represented animal phyla, and among plants, animals and fungi. The time estimate for the chordate-arthropod divergence, using 50 genes, is 993 +/- 46 Ma. Nematodes were found to have diverged from the lineage leading to arthropods and chordates at 1177 +/- 79 Ma. Phylogenetic analyses also show that a basal position of nematodes has strong support (p > 99%) and is not the result of rate biases. The three-way split (relationships unresolved) of plants, animals and fungi was estimated at 1576 +/- 88 Ma. By inference, the basal animal phyla (Porifera, Cnidaria, Ctenophora) diverged between about 1200-1500 Ma. This suggests that at least six animal phyla originated deep in the Precambrian, more than 400 million years earlier than their first appearance in the fossil record. (+info)
Isolation of the LEMMI9 gene and promoter analysis during a compatible plant-nematode interaction.
Plant-endoparasitic root-knot nematodes feed on specialized giant cells that they induce in the vascular cylinder of susceptible plants. Although it has been established that a number of plant genes change their expression pattern during giant cell differentiation, virtually no data are available about the mechanisms involved in that change. One possibility is differential promoter recognition by the transcription factor(s) responsible for the expression of specific genes. We have isolated and characterized a genomic clone from tomato containing the promoter region of LEMMI9, one of the few plant genes that have been reported to be highly expressed in galls (predominantly in giant cells). The analysis of transgenic potato plants carrying a LEMMI9 promoter-beta glucuronidase (GUS) fusion has demonstrated that the tomato promoter was activated in Meloidogyne incognita-induced galls in a heterologous system. We have located putative regulatory sequences in the promoter and have found that nuclear proteins from the galls formed specific DNA-protein complexes with the proximal region of the LEMMI9 promoter. The nuclear protein-binding sequence mapped to a region of 111 bp immediately upstream from the TATA box. This region contains a 12-bp repeat possibly involved in the formation of DNA-protein complexes, which might be related to the LEMMI9 transcriptional activation in the giant cells. (+info)
Polygalacturonase and polygalacturonase inhibitor protein: gene isolation and transcription in Glycine max-Heterodera glycines interactions.
The cell wall acts as the first line of defense during pathogen invasion. Polygalacturonases (PGs) are a class of cell-wall-modifying enzymes with precise temporal and organ-specific expression. A 350-bp fragment with high homology to PGs was identified by differential display (DD) analysis of soybean cyst nematode (SCN) race 3 resistant PI 437654 and susceptible cultivar Essex. The fragment was strongly expressed in Essex, 2 days after inoculation (DAI). Complete coding sequences of two PG cDNAs, PG1 and PG2, were isolated by 3' and 5' rapid amplification of cDNA ends polymerase chain reaction (RACE PCR). PI 437654 and Essex had identical PG1 and PG2 sequences. A transversion from A to C created a PstI restriction site in the PG2 cDNA that was used to distinguish the two PG cDNAs by cleaved amplified polymorphic sequence (CAPS) analysis. A cDNA encoding a polygalacturonase-inhibitor protein (PGIP) that is 89% identical to the Phaseolus vulgaris PGIP was isolated from soybean roots by reverse transcription (RT)-PCR. Steady-state levels of PG and PGIP were investigated by RNA gel blot analysis in roots 1 to 5 DAI and in hypocotyls and leaves. Differences in the constitutive levels of PG mRNAs were observed in roots of different soybean genotypes. Steady-state levels of PG mRNAs were enhanced during compatible interactions with SCN and reduced in incompatible interactions and in mechanically wounded roots. Enhanced PGIP transcription was observed in response to mechanical wounding in both PI 437654 and Essex, but only in compatible interactions with SCN, suggesting uncoupling of PGIP functions in developmental and stress cues. Constitutive expression in incompatible interactions shows PGIP is not a factor in SCN resistance. Thus, the up-regulation of endogenous PG transcription in soybean roots early after SCN infection could facilitate successful parasitism by SCN. (+info)
The planarian HOM/HOX homeobox genes (Plox) expressed along the anteroposterior axis.
In the freshwater planarian Dugesia japonica, five cDNAs for HOM/HOX homeobox genes were cloned and sequenced. Together with sequence data on HOM/HOX homeobox genes of platyhelminthes deposited in databases, comparison of the deduced amino acid sequences revealed that planarians have at least seven HOM/HOX homeobox genes, Plox1 to Plox7 (planarian HOM/HOX homeobox genes). Whole-mount in situ hybridization and RT-PCR revealed that Plox4 and Plox5 were increasingly expressed along a spatial gradient in the posterior region of intact animals. During regeneration, Plox5 was expressed only in the posterior region of regenerating body pieces, suggesting that the gene is involved in the anteroposterior patterning in planarians. Plox5 was not found to be expressed in a blastema-specific manner, which contradicts a previous report (J. R. Bayascas, E. Castillo, A. M. Munos-Marmol, and E. Salo. Development 124, 141-148, 1997). X-ray irradiation experiments showed that Plox5 was expressed at least in some cells other than neoblasts, but that the induction of Plox5 expression during regeneration might require neoblasts. (+info)
Apoptosis without caspases: an inefficient molecular guillotine?
Since the discovery that the cysteine protease CED-3 was essential for developmental death in the nematode C. elegans, the search has been on to identify homologous proteases governing mammalian apoptosis. Fourteen of these proteases, now called caspases, have been found to date, and studies with natural or chemical inhibitors, and more recently knock-out mice, confirmed the involvement of at least a subset of these proteases in various forms of mammalian apoptosis. However, there has been recent evidence that some apoptotic morphologies, such as cell shrinkage, membrane blebbing and nuclear condensation, are not blocked by caspase inhibitors and that the cells continue to die in a protracted and inefficient manner. This has led to the notion that caspases are not required for all aspects of apoptosis in mammals. Here we review the current knowledge about caspase-independent apoptosis, discuss the strengths and weaknesses of the reasoning that led to its proposition and provide insights into its possible regulation and physiological significance. (+info)
Wild rodents as experimental intermediate hosts of Lagochilascaris minor Leiper, 1909.
A total of 25 specimens of Cavia porcellus (guinea pig), 5 Dasyprocta agouti (agouti), and 22 Calomys callosus (vesper mice) were inoculated with infective eggs of Lagochilascaris minor. The inoculum was prepared with embryonated eggs and orally administered to each individual animal through an esophagus probe. In parallel, 100 specimens of Felis catus domesticus were individually fed with 55-70 nodules containing 3rd-stage larvae encysted in tissues of infected rodents. Animals were examined and necropsied at different time intervals. The migration and encystment of L3 larva was observed in viscera, skeletal muscle, adipose and subcutaneous tissues from all rodents. Adult worms localized at abscesses in the cervical region, rhino, and oropharynx were recovered from domestic cats inoculated with infected rodent tissues. Through this study we can conclude that: (1) wild rodents act as intermediate hosts, characterizing this ascarid heteroxenic cycle; (2) in natural conditions rodents could possibly act as either intermediate hosts or paratenic hosts of Lagochilascaris minor; (3) despite the occurrence of an auto-infecting cycle, in prime-infection of felines (definite hosts) the cycle is only completed when intermediate hosts are provided; and (4) in the wild, rodents could serve as a source of infection for humans as they are frequently used as food in regions with the highest incidence of human lagochilascariasis. (+info)
Studies on Procamallanus (Spirocamallanus) Pereirai annereaux, 1946 (Nematoda: Camallanidae), with new host records and new morphological data on the larval stages.
Larval stages and adults of Procamallanus (Spirocamallanus) pereirai Annereaux, 1946 are described from naturally infected Paralonchurus brasiliensis (Steindachner) (Sciaenidae) from the coast of the State of Rio de Janeiro, Brazil. The translucent first-stage larvae have a denticulate process at the anterior end, no buccal capsule or esophagus undifferentiated into anterior muscular and posterior glandular parts and an elongate tail; third-stage larvae have a tail with three terminal projections, a buccal capsule divided into an anterior portion with 12-20 ridges running to the left and a posterior smooth portion, and an esophagus with muscular and glandular regions. Fourth-stage larvae exhibit a buccal capsule lacking a distinct basal ring with ridges running to the right and a tail with two terminal processes, as in adults. New host records are reported and their role in its life-cycle are discussed. (+info)