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Not AvailableIn shrimp, which rely largely on their innate immune systemfor defense against invading pathogens, the Toll-pathwayhas been extensively studied, as it plays a crucial role ininnate immune responses. Different innate immune genesin the Toll-pathway of shrimp,Penaeus monodonviz., Toll-Like receptor (PmToll), Myeloid differentiation factor-88(PmMyD88), and Tumor necrosis factor receptor associatedfactor-6 (PmTRAF6) have been characterized and their rolein immune response against white spot syndrome virus hasbeen elucidated by real-time PCR-based expression analy-sis. In the current study, the role of these genes in theimmune response against bacteria was investigated bydetermining the mRNA expressions ofPmToll,PmMyD88,andPmTRAF6 in different tissues ofP. monodon, uponexperimental infection withVibrio harveyi, using real-timePCR. Seven tissues were selected, including hemocytes,lymphoid organ, gill, hepatopancreas, stomach, midgut, andhindgut. Significant upregulation of these genes wasobserved in hemocytes, lymphoid organ, and gut tissues atdifferent time-points after infection. Moreover, modulationof expression of the genes at different time-points could beobserved in primary cultured hemocytes in vitro upon expo-sure with pathogen-mimicking ligands (lipopolysacchridesand peptidoglycans). These experimental results indicate that the Toll-pathway plays an important role in the immune response against bacterial challenge.Not Availabl

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Not AvailableTransformer 2 (tra 2) and fruitless (fru) genes have been proven to play a key role in sex determination pathways in many Arthropods, including insects and crustaceans. In this study, a paralog of P. monodon tra 2 (Pmtra 2), P. monodon ovarian associated transformer 2 (PmOvtra 2) and 2 isoforms of P. monodon fruitless-like gene (Pmfru-1 and Pmfru-2) were identified and characterized. The full cDNA sequence of PmOvtra 2 consisted of 1,774 bp with the longest open reading frame (ORF) of 744 bp encoding for 247 amino acids. The PmOvtra 2 exhibited a predicted RNA-recognition motif (RRM) domain and two arginine-serine (RS) regions, suggesting its function in RNA splicing. The full cDNA sequence of Pmfru-1 consisted of 1,306 bp with 1,182 bp ORF encoding for 393 amino acids, whereas the full cDNA sequence of Pmfru-2 consisted of 1,858 bp with 1,437 bp ORF encoding 478 amino acids. The deduced amino acid sequences of Pmfru-1 and Pmfru-2 exhibited highly conserved domains of Fru proteins, including Broad-complex, Tramtrack and Bric-a-brac (BTB), and zinc finger (ZF) domains. In addition, Pmfru-1 and Pmfru-2 were suggestively originated from the same single genomic locus by genomic sequence analysis. Specifically, Pmfru pre-mRNA was alternatively spliced for Pmfru-1 and Pmfru-2 to include mutually exclusive exon 7 and exon 6, respectively. Temporal and spatial expression of PmOvtra 2, Pmfru-1, and Pmfru-2 were also investigated by qPCR. The results showed that all were expressed in early developmental stages with undifferentiated gonads starting from nauplius until postlarvae. The expression of PmOvtra 2 started at nauplius stage and gradually increased from mysis to postlarvae (PL) 1. However, the expression of Pmfru-1 was low at the nauplii stage and slightly increased from protozoea to PL5, whereas the expression of Pmfru-2 maintained a low level from nauplius to mysis and then gradually increased at the PL stages. Expressions of PmOvtra 2, Pmfru-1, and Pmfru-2 were detected in various tissues including nervous tissue, gill, heart, hepatopancreas, gut, and gonads. Interestingly, the sexually dimorphic expression of PmOvtra 2, Pmfru-1, and Pmfru-2 was demonstrated in fully developed gonads in which the ovary showed significantly higher expressions than the testis. The great difference in the expression pattern of PmOvtra 2, Pmfru-1, and Pmfru-2 in the ovary and testis suggested their roles in the female sex determination in P. monodon.Not Availabl

Variation in swimming speed of Escherichia coli in response to attractant

It is well known that Escherichia coli executes chemotactic motion in response to chemical cues by modulating the flagellar motor bias alone. However, previous studies have reported the possibility of variation in run speed in the presence of attractants although it is unclear whether bacteria can deliberately modulate their swimming speeds in response to environmental cues or if the motor speeds are hardwired. By studying the detailed motion of cells in a uniform concentration of glucose and its non-metabolizable analogue, we show that changing concentrations may be accompanied by variation in the swimming speed. For a fixed run duration, cells exposed to the attractants achieved a higher peak-swimming speed after a tumble compared with that in plain motility buffer. Our experiments using the mutant strain lacking the Trg sensor show no change in swimming speed with varying concentrations of the non-metabolizable analogue, suggesting that sensing may play a role in the observed variation of swimming speed

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Not AvailableIn the present study, ontogenetic expression of different innate immune genes in the Toll pathway of tiger shrimp, Penaeus monodon, such as TLR, myeloid differentiation factor 88 (MyD88) and tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6), was investigated in different developmental stages. Ontogenetic expression by real-time PCR revealed constitutive expression of these genes in all the developmental stages selected. TLR expression was found to be the highest in PL4, whereas MyD88 and TRAF6 showed the highest expression in eggs. The ubiquitous expression of TLR, MyD88 and TRAF6 in different developmental stages of P. monodon indicates the role of these genes in protecting the animals during early development. Immersion challenge of PL 18 with V. harveyi resulted in significant upregulation of TRAF6 at all time-points and significant upregulation of TLR at most of the time-points selected; however, MyD88 showed differential modulation pat- tern. In contrast to the bacterial challenge, WSSV infection in PL18 did not show any significant change in the expression of TRAF6, except for a downregulation observed at 12 to 48 hpi. However, TLR and MyD88 showed moderate increase in their expression, especially at late time-points. The responses of these genes to V. harveyi and WSSV immersion challenges in the juveniles (average body weight 3 g) of P. monodon were investigated in selected tissues including gill, hepatopancreas, and different parts of gastrointestinal tract such as foregut (stomach), midgut and hindgut. Temporal expression analysis revealed complete downregulation of PmMyD88 at most of the time-points in the gill following V. harveyi challenge and significant induction of PmTRAF6 at all time-points following WSSV infection. Immersion challenge with V. harveyi resulted in enhanced expression of TRAF6 in stomach and MyD88 in hepatopancreas showed similar pattern of expression post-WSSV challenge. Other tissues showed varying levels of induction of these genes at different time-points following pathogen challenge. The results of the present study suggest that both bacterial and viral challenges through immersion modulates the genes involved in the Toll pathway, and this might play an important role in the immune defense of post-larvae and juveniles of P. monodon.Not Availabl