Mapping QTL, epistasis and genotype?×?environment interaction of antioxidant activity, chlorophyll content and head formation in domesticated lettuce (Lactuca sativa)

Fruits and vegetables are rich sources of antioxidants in human diets and their intake is associated with chronic disease prevention. Lettuce (Lactuca sativa L.) is a common vegetable in diets worldwide, but its nutritional content is relatively low. To elucidate the genetic basis of antioxidant content in lettuce, we measured the oxygen radical absorbance capacity (ORAC) and chlorophyll (Chl) content as a proxy of β-carotene in an F₈ recombinant inbred line (RIL) in multiple production cycles at two different production sites. Plants were phenotyped at the open-leaf stage to measure genetic potential (GP) or at market maturity (MM) to measure the influence of head architecture (‘head’ or ‘open’). Main effect quantitative trait loci (QTL) were identified at MM (three Chl and one ORAC QTL) and GP (two ORAC QTL). No main effect QTL for Chl was detected at GP, but epistatic interaction was identified in one pair of marker intervals for each trait at GP. Interactions with environment were also detected for both main and epistatic effects (two for main effect, and one for epistatic effect). Main effect QTL for plant architecture and nutritional traits at MM colocated to a single genomic region. Chlorophyll contents and ORAC values at MM were significantly higher and Chl a to Chl b ratios were lower in ‘open’ types compared to ‘head’ types. The nutritional traits assessed for GP showed a significant association with plant architecture suggesting pleiotropic effects or closely linked genes. Taken together, the antioxidant and chlorophyll content of lettuce is controlled by complex mechanisms and participating alleles change depending on growth stage and production environment.     

A study of seed dispersal by flood flow in an artificially restored floodplain

Riverine floodplains play many important roles in river ecosystems. However, many floodplains have suffered degradation or loss of ecological function due to excessive river improvements or through changes in agricultural systems. As a result, many floodplain restoration projects are being conducted worldwide. One of the many methods being implemented to restore floodplain vegetation is flood water seed dispersal. In this technique, precisely estimating the effect of seed dispersal by flood water is important in order to achieve successful floodplain revegetation. Here, we focus our attention on sediment transport by flood water into the Azamenose Swamp, a restored floodplain. We attempt to estimate the function of seed deposition in the restored floodplain and explain how the seeds are deposited in the floodplain by flood water. The result suggests that the restored floodplain functions as a more appropriate deposition site for seeds than the riverbanks of the main river. It was also found that the distance from the inflow site and the weight of the sediment were related to seed deposition.     

Characterization of the rice blast resistance gene Pik cloned from Kanto51

To study similar, but distinct, plant disease resistance (R) specificities exhibited by allelic genes at the rice blast resistance locus Pik/Pikm, we cloned the Pik gene from rice cultivar Kanto51 and compared its molecular features with those of Pikm and of another Pik gene cloned from cv. Kusabue. Like Pikm, Pik is composed of two adjacent NBS-LRR (nucleotide-binding site, leucine-rich repeat) genes: the first gene, Pik1-KA, and the second gene, Pik2-KA. Pik from Kanto51 and Pik from Kusabue were not identical; although the predicted protein sequences of the second genes were identical, the sequences differed by three amino acids within the NBS domain of the first genes. The Pik proteins from Kanto51 and Kusabue differed from Pikm in eight and seven amino acids, respectively. Most of these substituted amino acids were within the coiled-coil (CC) and NBS domains encoded by the first gene. Of these substitutions, all within the CC domain were conserved between the two Pik proteins, whereas all within the NBS domain differed between them. Comparison of the two Pik proteins and Pikm suggests the importance of the CC domain in determining the resistance specificities of Pik and Pikm. This feature contrasts with that of most allelic or homologous NBS-LRR genes characterized to date, in which the major specificity determinant is believed to lie in the highly diverged LRR domain. In addition, our study revealed high evolutionary flexibility in the genome at the Pik locus, which may be relevant to the generation of new R specificities at this locus.     

The regulatory role of the auxin in the creeping chrysanthemum habit

The chrysanthemum (Dendranthema morifolium) variety ‘Yuhuajinhua’ has a creeping growth habit. An ELISA-based assessment of the content and distribution of IAA in the stem of ‘Yuhuajinhua’ showed that there was an IAA concentration gradient across the stem segment between the 2nd and 4th nodes, counting from the apex, before the creeping growth, while this difference disappeared after the initiation of creeping growth. An immunohistochemical assay for IAA showed that auxin was concentrated in the epidermis and cortex of the proximal side of the stem, particularly in the first few hours after gravitational stimulation was applied. The bending of the stem was generated by the asymmetric elongation of the epidermal cells in proximal side of the stem, especially upon to 6 h after gravistimulation, and this was probably mediated by an alteration in the IAA gradient across the stem. Exogenously applied 1-naphthaleneacetic acid (NAA) or 2,3,5-triiodobenzoic acid (TIBA) played converse effects on the gravitropic stem curvature. The data support the idea that IAA plays a crucial regulatory role in the formation of the creeping habit in the chrysanthemum variety ‘Yuhuajinhua’.     

Molecular characteristics of the <Emphasis Type="Italic">SLA-2</Emphasis> gene from Chinese Hebao pigs

To study the molecular characteristics of swine leukocyte antigen (SLA) class I from the Hebao pig, a rare inbreed in China, a pair of primers was designed to amplify the SLA-2 gene (SLA-2-HB) and then the molecular characteristics of the gene were analyzed by computer. After cloning, sequencing and computer analysis, four SLA-2-HB alleles were found, all of 1119 bp. Sites 3–1097 were an open reading frame encoding 364 amino acids with two sets of intra-chain disulfide bonds comprising four cysteines situated in sites 125, 188, 227 and 283. By alignment of SLA-2-HB sequences with other SLA-2 alleles in the DNA Data Bank of Japan/European Molecular Biology Laboratory/GenBank database, nine key variable amino acid sites were found in the extracellular domain of the SLA-2-HB alleles at sites 23(F), 24(I), 43(A), 44(K), 50(Q), 73(N), 95(I), 114(R) and 216(S), which could be used to differentiate other SLA-2 alleles. The amino acid identities between SLA-2-HB and other SLA-2, SLA-3 and SLA-1 alleles were 87.1–97.0%, 85.0–93.9% and 83.3–88.6%, respectively. The phylogenetic tree of SLA-2-HB showed that it was relatively independent of the other SLA-2 genes. Furthermore, the SLA-2-HB alleles were similar to HLA-B15 and HLA-A2 functional domains and preserved some functional sites of HLA-A2. It was concluded that SLA-2-HB is an allele of SLA-2 and that the Hebao pig might have evolved independently in China.     

A taxonomic revision of the genus Sinotrisus Yin & Li (Coleoptera, Staphylinidae, Pselaphinae)

The genus Sinotrisus Yin & Li, comprising four species, is redefined and revised. Members of Sinotrisus are often found with ants of the subfamily Formicinae, or in humid forest habitats. The type speciesand three new species are (re-)described and illustrated: Sinotrisus kishimotoi Yin & Nomura, sp. n. (China: Sichuan), Sinotrisus nomurai Yin, Li & Zhao (type species) (China: Zhejing), Sinotrisus sinensis Yin & Nomura, sp. n. (China: Sichuan) and Sinotrisus vietnamensis Yin & Nomura, sp. n. (Vietnam: Lai Chau). A key is included as an aid to distinguishing these species.     

Amoebal endosymbiont Protochlamydia induces apoptosis to human immortal HEp-2 cells

Protochlamydia, an environmental chlamydia and obligate amoebal endosymbiotic bacterium, evolved to survive within protist hosts, such as Acanthamobae, 700 million years ago. However, these bacteria do not live in vertebrates, including humans. This raises the possibility that interactions between Protochlamydia and human cells could induce a novel cytopathic effect, leading to new insights into host-parasite relationships. Therefore, we studied the effect of Protochlamydia on the survival of human immortal cell line, HEp-2 cells and primary peripheral blood mononuclear cells (PBMC). Using mainly 4',6-diamidino-2-phenylindole staining, fluorescent in situ hybridization, transmission electron microscopy, and also TUNEL and Transwell assays, we demonstrated that the Protochlamydia induced apoptosis in HEp-2 cells. The attachment of viable bacterial cells, but not an increase of bacterial infectious progenies within the cells, was required for the apoptosis. Other chlamydiae [Parachlamydia acanthamoebae and Chlamydia trachomatis (serovars D and L2)] did not induce the same phenomena, indicating that the observed apoptosis may be specific to the Protochlamydia. Furthermore, the bacteria had no effect on the survival of primary PBMCs collected from five volunteers, regardless of activation. We concluded that Protochlamydia induces apoptosis in human-immortal HEp-2 cells and that this endosymbiont could potentially be used as a biological tool for the elucidation of novel host-parasite relationships.