The coconut pathosystem: weed hosts of nymphs of the American palm Cixiid Haplaxius crudus (Hemiptera: Fulgoroidea)

Lethal yellowing (LY) of coconut palm (Cocos nucifera L., Arecaceae) is a disease of economic importance that is caused by the phytoplasma ‘Candidatus Phytoplasma palmae’ and is transmitted by the planthopper Haplaxius crudus (Van Duzee) (Hemiptera: Cixiidae). This study explores the weeds used by H. crudus nymphs and other Cixiidae in a coconut pathosystem in southern Mexico. Nymphs were collected directly from the root system of each weed by hand or with the help of a vacuum after carefully opening the culm. This study included 11 species of weeds: nine Poaceae [Brachiaria decumbens Stapf, B. humidicola (Rendle) Schweick, B. mutica (Forssk.) Stapf, Digitaria abyssinica (Hochst. Ex A. Rich.) Stapf, Eustachys petraea (Sw.) Desv., Leersia hexandra Sw., Panicum laxum Sw., P. maximum Jacq., Paspalum notatum Flüggé]; one Cyperaceae [Cyperus ligularis L.], and one Portulacaceae: [Portulaca pilosa L.]. Brachiaria mutica, E. petraea, B. humidicola, P. maximum were identified as the principal host species for H. crudus nymphs. Brachiaria decumbens, D. abyssinica, and C. ligularis are new host records for the nymphs of H. crudus. Additionally, it was found that H. crudus may coexist with its cogeners H. skarphion Kramer (Cixiidae) and H. caldwelli Kramer (Cixiidae), on B. mutica. On C. ligularis, H. crudus may coexist with Oecleus snowi Ball (Cixiidae) nymphs. These results suggest that in the coconut pathosystem there is a complex of multitrophic interactions that should be considered in integrated management of LY.     

New insights on the external features of egg capsules and embryo development in the squid Loligo vulgaris

The embryonic development of the squid Loligo vulgaris was observed from 183 egg masses collected from special devices deployed throughout Cabrera National Park (Baleares Islands, western Mediterranean Sea). Sequence alignment analysis of the cytochrome oxidase I gene revealed that all embryos belonged to L. vulgaris. In total, 549 egg capsules were examined. Viable egg capsules (n = 420) were classified into one of five maturation stages according to the primary external features. The length of the viable egg capsules varied between 40 and 170 mm, and increased with embryonic development. The non-viable capsules (n = 129) were categorized into four groups: I (Ginger root), non-viable II and III, and empty egg capsule (IV). The percentage of non-viable capsules (i.e. grades I, II and III) was 92.25%. Empty capsules accounted for 7.75% of the total non-viable egg capsules. Embryonic development was classified into a second scale of eight stages. Egg capsule stage and embryonic stage were significantly related (n = 420; p < 0.001), facilitating the determination of the embryo developmental phase based on the outward appearance of the egg capsules. The embryo development stage based on the external features of the egg capsules might constitute an innovative tool for in situ embryological data collection. This new method is neither time consuming nor invasive, and could be helpful in fishing cruises, for scuba diving visual census in natural habitats and for laboratory culture. Slight variability in the developmental embryonic stages within egg capsules from the same egg mass was identified. The origin of this asynchrony is discussed. Chronological appearance of organs was similar to that of the six loliginid species previously examined. However, some developmental changes in the timing or rate of events (heterochronies) were observed: Hoyle’s organ was formed earlier in L. vulgaris and the appearance of ventral chromatophores was slightly delayed (2 days) compared with the other species considered.     

Routes and machinery of primary cilium biogenesis

Primary cilia are solitary, microtubule-based protrusions of the cell surface that play fundamental roles as photosensors, mechanosensors and biochemical sensors. Primary cilia dysfunction results in a long list of developmental and degenerative disorders that combine to give rise to a large spectrum of human diseases affecting almost any major body organ. Depending on the cell type, primary ciliogenesis is initiated intracellularly, as in fibroblasts, or at the cell surface, as in renal polarized epithelial cells. In this review, we have focused on the routes of primary ciliogenesis placing particular emphasis on the recently described pathway in renal polarized epithelial cells by which the midbody remnant resulting from a previous cell division event enables the centrosome for initiation of primary cilium assembly. The protein machinery implicated in primary cilium formation in epithelial cells, including the machinery best known for its involvement in establishing cell polarity and polarized membrane trafficking, is also discussed.     

Clones identification of Sequoia sempervirens (D. Don) Endl. in Chile by using PCR-RAPDs technique

A protocol of polymerase chain reaction-random amplified polymorphic DNAs (PCR-RAPDs) was established to analyse the gene diversity and genotype identification for clones of Sequoia sempervirens (D. Don) Endl. in Chile. Ten (out of 34) clones from introduction trial located in Voipir-Villarrica, Chile, were studied. The PCR-RAPDs technique and a modified hexadecyltrimethylammonium bromide (CTAB) protocol were used for genomic DNA extraction. The PCR tests were carried out employing 10-mer random primers. The amplification products were detected by electrophoresis in agarose gels. Forty nine polymorphic bands were obtained with the selected primers (BG04, BF07, BF12, BF13, and BF14) and were ordered according to their molecular size. The genetic similarity between samples was calculated by the Jaccard index and a dendrogram was constructed using a cluster analysis of unweighted pair group method using arithmetic averages (UPGMA). Of the primers tested, 5 (out of 60) RAPD primers were selected for their reproducibility and high polymorphism. A total of 49 polymorphic RAPD bands were detected out of 252 bands. The genetic similarity analysis demonstrates an extensive genetic variability between the tested clones and the dendrogram depicts the genetic relationships among the clones, suggesting a geographic relationship. The results indicate that the RAPD markers permitted the identification of the assayed clones, although they are derived from the same geographic origin.     

Reactive oxygen species produced by NADPH oxidase regulate plant cell growth

Cell expansion is a central process in plant morphogenesis, and the elongation of roots and root hairs is essential for uptake of minerals and water from the soil. Ca2+ influx from the extracellular store is required for (and sets the rates of) cell elongation in roots. Arabidopsis thaliana rhd2 mutants are defective in Ca2+ uptake and consequently cell expansion is compromised--rhd2 mutants have short root hairs and stunted roots. To determine the regulation of Ca2+ acquisition in growing root cells we show here that RHD2 is an NADPH oxidase, a protein that transfers electrons from NADPH to an electron acceptor leading to the formation of reactive oxygen species (ROS). We show that ROS accumulate in growing wild-type (WT) root hairs but their levels are markedly decreased in rhd2 mutants. Blocking the activity of the NADPH oxidase with diphenylene iodonium (DPI) inhibits ROS formation and phenocopies Rhd2-. Treatment of rhd2 roots with ROS partly suppresses the mutant phenotype and stimulates the activity of plasma membrane hyperpolarization-activated Ca2+ channels, the predominant root Ca2+ acquisition system. This indicates that NADPH oxidases control development by making ROS that regulate plant cell expansion through the activation of Ca2+ channels.     

Breeding in the gray-headed tody-flycatcher (Aves: Tyrannidae) with comments on geographical variation in reproductive traits within the genus Todirostrum

The gray-headed tody-flycatcher Todirostrum poliocephalum is a passerine endemic to the Atlantic Forest of Brazil. We describe the nest and nesting behaviour of this species and investigate geographical variation in breeding traits in the genus using data from the literature, museum collections, and citizen science projects. We located 21 nests of the gray-headed tody-flycatcher, 13 of which we monitored. Nest height above the ground averaged 3.3 ± 3.4 m (n = 21). Nests were built over a 16.8 ± 5.6-day period (n = 6) by both adults. Clutch sizes ranged from two to three eggs, with a mean of 2.9 ± 0.3 eggs (n = 10). Eggs measured 16.6 ± 0.5 × 12.0 ± 0.5 mm (n = 23) and weighed 1.1 ± 0.1 g (n = 19). Mean incubation period was 17 days (n = 3) and mean nestling period was 15.5 days (n = 2). Apparent reproductive success was 30.8%, with predation being the primary cause of nest failure (46.1%). Mayfield’s reproductive success was 25.9%, and daily survival rates for eggs and nestlings were 0.957 and 0.971, respectively. Clutch sizes increased with latitude, but temperature and precipitation seasonality had very low importance in explaining clutch size variation.     

Genome-wide association defines more than 30 distinct susceptibility loci for Crohn's disease

Several risk factors for Crohn's disease have been identified in recent genome-wide association studies. To advance gene discovery further, we combined data from three studies on Crohn's disease (a total of 3,230 cases and 4,829 controls) and carried out replication in 3,664 independent cases with a mixture of population-based and family-based controls. The results strongly confirm 11 previously reported loci and provide genome-wide significant evidence for 21 additional loci, including the regions containing STAT3, JAK2, ICOSLG, CDKAL1 and ITLN1. The expanded molecular understanding of the basis of this disease offers promise for informed therapeutic development.     

Network modeling links breast cancer susceptibility and centrosome dysfunction

Many cancer-associated genes remain to be identified to clarify the underlying molecular mechanisms of cancer susceptibility and progression. Better understanding is also required of how mutations in cancer genes affect their products in the context of complex cellular networks. Here we have used a network modeling strategy to identify genes potentially associated with higher risk of breast cancer. Starting with four known genes encoding tumor suppressors of breast cancer, we combined gene expression profiling with functional genomic and proteomic (or 'omic') data from various species to generate a network containing 118 genes linked by 866 potential functional associations. This network shows higher connectivity than expected by chance, suggesting that its components function in biologically related pathways. One of the components of the network is HMMR, encoding a centrosome subunit, for which we demonstrate previously unknown functional associations with the breast cancer-associated gene BRCA1. Two case-control studies of incident breast cancer indicate that the HMMR locus is associated with higher risk of breast cancer in humans. Our network modeling strategy should be useful for the discovery of additional cancer-associated genes.