Protein differences detected by two-dimensional electrophoresis in the species complex of Schizotetranychus celarius (Banks)

The species complex of Schizotetranychus celarius (Banks) has been thought to involve three morphologically distinct species, S. celarius, Schizotetranychus longus Sait and Schizotetranychus miscanthi Sait. Furthermore, the former species includes at least three morphs which have not yet been examined taxonomically. In the present study, the protein differences of these species and morphs were examined using two-dimensional electrophoresis. In comparison of protein spot patterns between 11 populations of the S. celarius complex and Schizotetranychus recki Ehara, the former group appeared to be very different to S. recki. The phenogram made based on genetic distance suggested that the species complex includes at least two subgroups: S. miscanthi and S. longus. These results are consistent with the previous taxonomic study. On the other hand, the morphs which had been categorized as S. celarius did not form a distinct cluster.This study was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education. Science and Cultures, Japan (No. 02640501) and from the Ministry of Agriculture, Forestry and Fisheries (Bio Cosmos Program, BCP-93-I-B-14), and it is the contribution No. E-163 of the Fruit Tree Research Station.     

Ultimate Drivers and Proximate Correlates of Polyandry in Predatory Mites

Polyandry is more widespread than anticipated from Bateman’s principle but its ultimate (evolutionary) causes and proximate (mechanistic) correlates are more difficult to pinpoint than those of polygyny. Here, we combined mating experiments, quantification of reproductive traits and microsatellite genotyping to determine the fitness implications of polyandry in two predatory mite species, where males are highly polygynous (up to 45 fertilized females during life), whereas females range from monandry to various polyandry levels. The medium-level polyandrous (up to eight male mates possible) Neoseiulus californicus received clear direct and indirect benefits: multiply mated females produced more offspring with higher survival chances over longer times than singly mated females. In contrast, singly and multiply mated females of the low-level polyandrous (commonly two male mates at maximum) Phytoseiulus persimilis produced similar numbers of offspring having similar survival chances. In both species, multiple mating resulted in mixed offspring paternities, opening the chance for indirect fitness benefits such as enhanced genetic compatibility, complementarity and/or variability. However, the female re-mating likelihood and the paternity chance of non-first male mates were lower in P. persimilis than in N. californicus. Regarding proximate factors, in both species first mating duration and female re-mating likelihood were negatively correlated. Based on occasional fertilization failure of first male mates in P. persimilis, and mixed offspring paternities in both species, we argue that fertilization assurance and the chance to gain indirect fitness benefits are the ultimate drivers of polyandry in P. persimilis, whereas those of N. californicus are higher offspring numbers coupled with enhanced offspring viability and possibly other indirect fitness benefits. Overall, the adaptive significance and proximate events well reflected the polyandry levels. Our study provides a key example for linking behavioral experiments, quantification of reproductive traits and paternity analysis via offspring genotyping to explain the evolution of differing levels of polyandry.     

Secondary xylem-specific expression of caffeoyl-coenzyme A 3-O-methyltransferase plays an important role in the methylation pathway associated with lignin biosynthesis in loblolly pine

Two types of structurally distinct O-methyltransferases mediate the methylation of hydroxylated monomeric lignin precursors in angiosperms. Caffeate 3-O-methyltransferase (COMT; EC 2.1.1.68) methylates the free acids and caffeoyl CoA 3-O-methyltransferase (CCoAOMT; EC 2.1.1.104) methylates coenzyme A esters. Recently, we reported a novel hydroxycinnamic acid/hydroxycinnamoyl CoA ester O-methyltransferase (AEOMT) from loblolly pine differentiating xylem that was capable of methylating both acid and ester precursors with similar efficiency. In order to determine the possible existence and role of CCoAOMT in lignin biosynthesis in gymnosperms, a 1.3 kb CCoAOMT cDNA was isolated from loblolly pine that showed 79–82% amino acid sequence identity with many angiosperm CCoAOMTs. The recombinant CCoAOMT expressed in Escherichia coli exhibited a significant methylating activity with hydroxycinnamoyl CoA esters whereas activity with hydroxycinnamic acids was insignificant. Moreover, 3.2 times higher catalytic efficiency for methylating caffeoyl CoA over 5-hydroxyferuloyl CoA was observed which could serve as a driving force towards synthesis of guaiacyl lignin. The secondary xylem-specific expression of CCoAOMT was demonstrated using RNA blot analysis, western blot analysis, and O-methyltransferase enzyme assays. In addition, Southern blot analysis indicated that CCoAOMT may exist as a single-copy gene in loblolly pine genome. The transgenic tobacco plants carrying loblolly pine CCoAOMT promoter-GUS fusion localized the site of GUS activity at the secondary xylem tissues. These data suggest that CCoAOMT, in addition to AEOMT, plays an important role in the methylation pathway associated with lignin biosynthesis in loblolly pine.     

The effects of prestarvation diet on starvation tolerance of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae)

Understanding the factors affecting stress tolerance in phytoseiid mites is critical for their integration into biological control programs. In the present study, the effects of diet (varying in prey species, physiological status and phenotype) are examined on the future starvation tolerance of the predatory mite Neoseiulus californicus McGregor (Acari: Phytoseiidae). The predators are fed from egg to adulthood on diapausing or nondiapausing Tetranychus urticae, Tetranychus kanzawai (wild and albino strains) or the nondiapausing species Panonychus citri (wild and albino strains). Thereafter, 3‐day‐old mated adult females are held without food at 25 ± 1 °C and a relative humidity of 98 ± 2%. The survival of these starved females is observed daily until all females have died. The survival curves and mean survival times of N. californicus are found to vary among prey types and are significantly longer when the predator is fed with diapausing prey. This enhanced survival is consistent with high concentrations of glycogen and triacylglyceride in the body of the predator at the onset of starvation. The predators fed nondiapausing prey have shorter survival times, and the glycogen and triacylglyceride contents in their bodies are low or undetectable. The protein contents of the predator's body are similar after consuming different prey types, except for a high concentration when fed the albino strain of P. citri. Protein content is unlikely to play a direct role in starvation tolerance, although it may affect the response to varying glycogen and triacylglyceride levels. These findings indicate that nutritional value of prey has a strong impact on the starvation tolerance of N. californicus.     

Isolation of 4-coumarate Co-A ligase gene promoter from loblolly pine (Pinus taeda) and characterization of tissue-specific activity in transgenic tobacco

We characterized promoter activity of a phenylpropanoid biosynthetic gene encoding 4-coumarate Co-A ligase (4CL), Pta4Clα, from Pinus taeda. Histochemical- and quantitative assays of GUS expression in the vascular tissue were performed using transgenic tobacco plants expressing promoter-GUS reporters. Deletion analysis of the Pta4Clα promoter showed that the region ?524 to ?252, which has two AC elements, controls the high expression levels in ray-parenchyma cells of older tobacco stems. High activity level of the promoter domain of Pta4CLα was also detected in the xylem cells under bending stress. DNA-protein complexes were detected in the reactions of the Pta4CLα promoter fragments with the nuclear proteins of xylem of P. taeda. The AC elements in the Pta4CLα promoter appeared to have individual roles during xylem development that are activated in a coordinated manner in response to stress in transgenic tobacco.     

Evidence of a high level of gene flow among apple trees in <Emphasis Type="Italic">Tetranychus urticae</Emphasis>

The dispersal mechanism of the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) could affect predator–prey population dynamics and the spread of acaricide resistance. To investigate the propensity for spider mite migration in the field, the genetic structure of spider mite populations was studied in two apple orchards using five microsatellite markers. Adult female mites were collected from trees separated by approximately 10–24 m along a line covering a distance of about 100 m. The genetic data suggested that a high population density increased the migration rate among the breeding colonies within a single tree. Spatial autocorrelation analysis suggested a positive genetic structure in the first distance class within the two orchards, which might have been caused by crawling or short-distance aerial dispersal. Meanwhile, mites may also have a large-scale migration system that could cause a high level of gene flow and constrained isolation-by-distance or genetic clines within the approximately 100-m range of the study sites. Therefore, mites might aerially disperse over long distances on a scale of <100 m while also taking shorter trips among nearby trees within a distance of 10–24 m in the apple orchards.     

Functional Analysis of an Arabidopsis thaliana Abiotic Stress-inducible Facilitated Diffusion Transporter for Monosaccharides

Sugars play indispensable roles in biological reactions and are distributed into various tissues or organelles via transporters in plants. Under abiotic stress conditions, plants accumulate sugars as a means to increase stress tolerance. Here, we report an abiotic stress-inducible transporter for monosaccharides from Arabidopsis thaliana that is termed ESL1 (ERD six-like 1). Expression of ESL1 was induced under drought and high salinity conditions and with exogenous application of abscisic acid. Promoter analyses using β-glucuronidase and green fluorescent protein reporters revealed that ESL1 is mainly expressed in pericycle and xylem parenchyma cells. The fluorescence of ESL1-green fluorescent protein-fused protein was detected at tonoplast in transgenic Arabidopsis plants and tobacco BY-2 cells. Furthermore, alanine-scanning mutagenesis revealed that an N-terminal LXXXLL motif in ESL1 was essential for its localization at the tonoplast. Transgenic BY-2 cells expressing mutated ESL1, which was localized at the plasma membrane, showed an uptake ability for monosaccharides. Moreover, the value of K_m for glucose uptake activity of mutated ESL1 in the transgenic BY-2 cells was extraordinarily high, and the transport activity was independent from a proton gradient. These results indicate that ESL1 is a low affinity facilitated diffusion transporter. Finally, we detected that vacuolar invertase activity was increased under abiotic stress conditions, and the expression patterns of vacuolar invertase genes were similar to that of ESL1. Under abiotic stress conditions, ESL1 might function coordinately with the vacuolar invertase to regulate osmotic pressure by affecting the accumulation of sugar in plant cells.     

Increased frequency of homologous recombination and T-DNA integration in Arabidopsis CAF-1 mutants

Chromatin assembly factor 1 (CAF-1) is involved in nucleo some assembly following DNA replication and nucleotide excision repair. In Arabidopsis thaliana, the three CAF-1 subunits are encoded by FAS1, FAS2 and, most likely, MSI1, respectively. In this study, we asked whether genomic stability is altered in fas1 and fas2 mutants that are lacking CAF-1 activity. Depletion of either subunit increased the frequency of somatic homologous recombination (HR) in planta approximately 40-fold. The frequency of transferred DNA (T-DNA) integration was also elevated. A delay in loading histones onto newly replicated or repaired DNA might make these DNA stretches more accessible, both to repair enzymes and to foreign DNA. Furthermore, fas mutants exhibited increased levels of DNA double-strand breaks, a G2-phase retardation that accelerates endoreduplication, and elevated levels of mRNAs coding for proteins involved in HR-all factors that could also contribute to upregulation of HR frequency in fas mutants.