The genome sequence of the protostome Daphnia pulex encodes respective orthologues of a neurotrophin, a Trk and a p75NTR: Evolution of neurotrophin signaling components and related proteins in the bilateria

Background

Neurotrophins and their Trk and p75NTR receptors play an important role in the nervous system. To date, neurotrophins, Trk and p75NTR have only been found concomitantly in deuterostomes. In protostomes, homologues to either neurotrophin, Trk or p75NTR are reported but their phylogenetic relationship to deuterostome neurotrophin signaling components is unclear. Drosophila has neurotrophin homologues called Spätzles (Spz), some of which were recently renamed neurotrophins, but direct proof that these are deuterostome neurotrophin orthologues is lacking. Trks belong to the receptor tyrosine kinase (RTK) family and among RTKs, Trks and RORs are closest related. Flies lack Trks but have ROR and ROR-related proteins called NRKs playing a neurotrophic role. Mollusks have so far the most similar proteins to Trks (Lymnaea Trk and Aplysia Trkl) but the exact phylogenetic relationship of mollusk Trks to each other and to vertebrate Trks is unknown. p75NTR belongs to the tumor necrosis factor receptor (TNFR) superfamily. The divergence of the TNFR families in vertebrates has been suggested to parallel the emergence of the adaptive immune system. Only one TNFR representative, the Drosophila Wengen, has been found in protostomes. To clarify the evolution of neurotrophin signaling components in bilateria, this work analyzes the genome of the crustacean Daphnia pulex as well as new genetic data from protostomes.

Results

The Daphnia genome encodes a neurotrophin, p75NTR and Trk orthologue together with Trkl, ROR, and NRK-RTKs. Drosophila Spz1, 2, 3, 5, 6 orthologues as well as two new groups of Spz proteins (Spz7 and 8) are also found in the Daphnia genome. Searching genbank and the genomes of Capitella, Helobdella and Lottia reveals neurotrophin signaling components in other protostomes.

Conclusion

It appears that a neurotrophin, Trk and p75NTR existed at the protostome/deuterostome split. In protostomes, a "neurotrophin superfamily" includes Spzs and neurotrophins which respectively form two paralogous families. Trks and Trkl proteins also form closely related paralogous families within the protostomian RTKs, whereby Trkls are absent in deuterostomes. The finding of p75NTR in several protostomes suggests that death domain TNFR superfamily proteins appeared early in evolution.     

Cyanobacterial diversity in the rhizosphere of rice and its ecological significance

This investigation was undertaken to characterize the abundance and genera-wise diversity of cyanobacteria in the rice rhizosphere and nitrogen-fixing ability of the isolated strains. The cyanobacterial strains belonging to the genera Nostoc and Anabaena comprised 80% of the rhizosphere isolates, which were also efficient in enhancing the germination and growth of wheat seeds and exhibited significantly high protein accumulation and IAA production. Distinct profiles for the cyanobacterial strains were obtained on amplification with extended Hip 1 primer — HipTG, indicative of the diversity among these strains. Our investigation helped in identifying promising cyanobacterial isolates from the rhizosphere of rice, which can be utilized in developing efficient plant growth promoting cyanobacterial inoculants.     

Identification and cross-species amplification of EST derived SSR markers in different bamboo species

The availability of expressed sequence data derived from gene discovery programs became an alternative source of mining simple sequence repeat (SSR) and developing inexpensive genetic markers for the crop improvements. In present study, 10 express sequence tags (EST)-SSR markers were identified from Bambusa oldhamii public sequence data base. Transferability to 25 species of Bambusoideae ranged from 30% to 100%. The number of alleles detected per locus ranged from 2 to 10. All the newly identified SSR markers were found to be moderately to highly polymorphic with an average Polymorphic Information Content (PIC) value of 0.54. As these loci represents transcribed region and recorded high level of cross transferability and reliable amplification across the species, demonstrating the utility of these markers for functional and genetic analyses of bamboo species.     

Inheritance of seed yield and quality traits in peas (Pisum sativum L.)

Summary A half diallel analysis involving nine cultivars showed that additive as well as non-additive gene effects were important for the inheritance of seed yield per plant, 100-seed weights, protein content and potassium per cent. For remaining traits non-additive genetic components were important. Overdominance was observed for all traits except for 100-seed weight, which expressed partial dominance. Parents PMR-T10, EC21857, EC109182, T163 and EC109189 were good general combiners for seed yield, seed weight and quality traits. In general there was a good relationship between per se performance and the gca effects of the parents for all traits. Cross combinations such as LMR8 x EC109182,LMR8 x PMR-T10,LMR8 x EC21857,PMRT10 x EC21857 and P23 x EC21857 were found promising. The seed yield was positively correlated with other quality traits. Protein had a positive correlation with methionine and phosphorus. All the values of correlation co-efficients were non-significant except for yield with potassium, 100-seed weight and protein with methionine, indicating that yield and quality attributes can be improved simultaneously by simple selection procedures.     

Metabolism of Monoterpenes : Early Steps in the Metabolism of d-Neomenthyl-beta-d-Glucoside in Peppermint (Mentha piperita) Rhizomes

Previous studies have shown that the monoterpene ketone l-[G-³H] menthone is reduced to the epimeric alcohols l-menthol and d-neomenthol in leaves of flowering peppermint (Mentha piperita L.), and that a portion of the menthol is converted to menthyl acetate while the bulk of the neomenthol is transformed to neomenthyl-β-d-glucoside which is then transported to the rhizome (Croteau, Martinkus 1979 Plant Physiol 64: 169-175). Analysis of the disposition of l-[G-³H]menthone applied to midstem leaves of intact flowering plants allowed the kinetics of synthesis and transport of the monoterpenyl glucoside to be determined, and gave strong indication that the glucoside was subsequently metabolized in the rhizome. Studies with d-[G-³H]neomenthyl-β-d-glucoside as substrate, using excised rhizomes or rhizome segments, confirmed the hydrolysis of the glucoside as an early step in metabolism at this site, and revealed that the terpenoid moiety was further converted to a series of ether-soluble, methanol-soluble, and water-soluble products. Studies with d-[G-³H]neomenthol as the substrate, using excised rhizomes, showed the subsequent metabolic steps to involve oxidation of the alcohol back to menthone, followed by an unusual lactonization reaction in which oxygen is inserted between the carbonyl carbon and the carbon bearing the isopropyl group, to afford 3,4-menthone lactone. The conversion of menthone to the lactone, and of the lactone to more polar products, were confirmed in vivo using l-[G-³H]menthone and l-[G-³H]-3,4-menthone lactone as substrates. Additional oxidation products were formed in vivo via the desaturation of labeled neomenthol and/or menthone, but none of these transformations appeared to lead to ring opening of the p-menthane skeleton. Each step in the main reaction sequence, from hydrolysis of neomenthyl glucoside to lactonization of menthone, was demonstrated in cell-free extracts from the rhizomes of flowering mint plants. The lactonization step is of particular significance in providing a means of cleaving the p-menthane ring to afford an acyclic carbon skeleton that can be further degraded by modifications of the well-known β-oxidation sequence.     

Studies in the embryology of the diandrous orchidCypripedium cordigerum (Cypripedieae,Orchidaceae)

The anther wall layers ofCypripedium cordigerum are six to eight. The glandular tapetum is 2- or 3-layered and its cells are uninucleate. Simultaneous cytokinesis results in decussate, isobilateral and tetrahedral pollen tetrads. Ripe pollen grains are 2-celled. The mature ovules are anatropous, bitegmic and tenuinucellate. Both the integuments are dermal in origin and 2-layered. The inner integument alone forms the micropyle. The female gametophyte is 6-nucleate and bisporic. The reduction of nuclei is due to the strike phenomenon. Double fertilization occurs. The primary endosperm nucleus divides to form two free endosperm nuclei. The mature embryo is undifferentiated. The cells ca, m and n contribute to the embryo. The suspensor is single-celled. The seed coat is formed entirely by the outer layer of the outer integument. There are three sterile and three fertile valves in the ovary. In the prefertilization stages these valves consist of parenchymatous cells with starch and raphides. After fertilization, the sterile valves develop sclerotic cells whereas the fertile valves remain parenchymatous. The pericarp structure and embryological features support the retention of tribeCypripedieae within theOrchidaceae.     

The metabolism and biological activity of a 9-substituted cytokinin

In order to test the metabolic stability of 9-substituted cytokinins, 6-benzylamino-9-methyl purine has been synthesized and labeled with ¹⁴C in the 9-methyl carbon or doubly labeled with ¹⁴C in the 9-methyl carbon and ³H in the methylene moiety of the side chain. Although the 6-benzylamino-9-methylpurine is chemically stable, cytokinin-requiring tissues begin removing the 9-substituent in as little as 10 minutes. Among the various metabolic products is free benzylaminopurine. Thus, the biological activity of 9-substituted cytokinins could be accounted for by their conversion to the free base.     

Experimental candidal mastitis in goats: Clinical,haematological, biochemical and sequential pathological studies

The present study, first of its kind, was conducted with the objectives to understand hitherto little known aspects of candidal mastitis, like its sequential pathology, pathogenesis and clinico-biochemical changes. For this purpose, unilateral intramammary inoculation of 10 goats with Candida albicans (1.2 × 10⁷ yeast cells) resulted in the development of mastitis, with gross and microscopic lesions being restricted to the infected udder halves only and without dissemination of infection to the opposite uninfected udder halves as well as other organs of the body. The experiment was continued for 40 days and after infection, there was sharp fall in milk yield and Candida albicans was directly demonstrated in the milk and re-isolated from the milk and udder tissues up to 30th day after inoculation. An increase in total immunoglobulins in the milk and plasma along with increase in total plasma proteins were also observed. Haematology revealed leukocytosis and neutrophilia. Microscopically, there was acute purulent mastitis, which later became chronic, nonpurulent and interstitial with formation of granulomas. It was concluded that Candida albicans was highly pathogenic to the lactating goat mammary gland even without immunosuppression or antibiotic treatment, resulting in severe irreversible tissue damage and nearly complete agalactia. This revised version was published online in August 2006 with corrections to the Cover Date.