Genetic diversity in the Indian population of Penaeus monodon (Fabricius, 1798) as revealed by mtDNA sequence analysis

Genetic diversity in the Indian population of the tiger shrimp Penaeus monodon was determined by using partial sequence data of the mitochondrial DNA (mtDNA) control region (D‐loop) and the 16S rRNA gene. Eight populations from different geographical locations (Mumbai, Kochi, Mangalore, Kakinada, Gopalpur, Chilika, Paradeep and Andaman) were collected and analysed. The amplified polymerase chain reaction products of size 577 bp for the control region and 472 bp for 16S rRNA were sequenced in both directions and data were analysed through clustal , arlequin , mega and phylip . A significant genetic structure was found among the Indian populations. The mtDNA control region proved to be a powerful marker in comparison with 16S rRNA for population studies of this species. The east coast population was more genetically diverse than the west coast. The Andaman population was found to be the most diverse among all the populations. The populations on the west coast were found to be genetically more structured and differentiated than the populations on the east coast. The results revealed a high level of genetic diversity and also distinct population structuring of P. monodon, suggesting great possibilities of genetic improvement for growth and other economic traits.     

Siah regulation of Pard3A controls neuronal cell adhesion during germinal zone exit

The brain's circuitry is established by directed migration and synaptogenesis of neurons during development. Although neurons mature and migrate in specific patterns, little is known about how neurons exit their germinal zone niche. We found that cerebellar granule neuron germinal zone exit is regulated by proteasomal degradation of Pard3A by the Seven in Absentia homolog (Siah) E3 ubiquitin ligase. Pard3A gain of function and Siah loss of function induce precocious radial migration. Time-lapse imaging using a probe to measure neuronal cell contact reveals that Pard3A promotes adhesive interactions needed for germinal zone exit by recruiting the epithelial tight junction adhesion molecule C to the neuronal cell surface. Our findings define a Siah-Pard3A signaling pathway that controls adhesion-dependent exit of neuronal progenitors or immature neurons from a germinal zone niche.     

Quantification of viable <Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter asiaticus in hosts using quantitative PCR with the aid of ethidium monoazide (EMA)

Citrus Huanglongbing (HLB) is a devastating disease of citrus known to be associated with a fastidious, phloem-limited Gram-negative, yet to be cultured bacterium in the genus Candidatus Liberibacter. In the present study we have developed a method to quantify viable Candidatus Liberibacter asiaticus (Las) with the aid of ethidium monoazide (EMA) which can differentiate live from dead cells. First, calibration curves were developed with the aid of quantitative real-time PCR (QPCR) by using a plasmid template consisting of a 703 bp DNA fragment of rplKAJL-rpoBC (β-operon) region. Standard equations were then developed to quantify Las genome equivalents in citrus, periwinkle, and Asian citrus psyllid, Diaphorina citri. To overcome the limitation of quantitative PCR in discriminating between live and dead bacterial cells, EMA was used to inhibit the amplification of DNA from the dead cells of Las in plant samples. By using the standard equations and EMA-QPCR methods developed in this study, we found that the proportion of viable cells in citrus and periwinkle ranged from 17–31% and 16–28%, respectively. It was determined that a minimum bacterial concentration is required for HLB symptom development by quantifying the population of Las in symptomatic and asymptomatic leaves. The EMA-QPCR methodology developed in the present study should provide an accurate assessment of viable HLB pathogen, providing a tool to investigate disease epidemiology and thus act as a crucial component for disease assessment and management. The authors P. Trivedi and U. S. Sagaram contributed equally to this work.     

Development of ISSR- and RAPD-derived SCAR markers for identification of Gladiolus germplasm

Gladiolus is an economically important ornamental crop, cultivated for its beautiful flowers throughout the world. The correct genotype identification of plant material is very significant for the floriculture industry. The aim of this study was to develop sequence-characterised amplified region (SCAR) markers from RAPD and ISSR fragments for identification and authentication of Gladiolus germplasm. The SCAR markers developed could be easily employed as valuable tools to identify newly developed Gladiolus cultivars. The SCAR markers, viz. ScG12, ScG34, and ScG36, are specific to the DNA from all 62 Gladiolus cultivars, as they did not amplify the DNA of other taxa of the family Iridaceae, including Iris, Amaryllis, and Narcissus. All three SCAR markers distinguished Gladiolus from other taxa of the family Iridaceae, whereas marker ScAm was specific to the ‘Amethyst’ cultivar. Our results confirmed that this particular SCAR marker distinguished the ‘Amethyst’ cultivar from the other 62 Gladiolus cultivars investigated in the present study. This development of SCAR markers based on RAPD and ISSR markers seems to be the maiden attempt for Gladiolus cultivars.     

Natural daylight restricted to twilights delays the timing of testicular regression but does not affect the timing of the daily activity rhythm of the house sparrow (Passer domesticus)

Background  

A stable and systematic daily change in light levels at dawn and dusk provides the most reliable indicator of the phase of the day. It is likely that organisms have evolved mechanisms to use these twilight transitions as the primary zeitgeber to adjust their circadian phases. In this study, we investigated under natural illumination conditions the effects of daylight exposure restricted to twilights on the timing of testicular regression and locomotor activity of the house sparrow (Passer domesticus), which possesses a strongly self-sustaining circadian system.