Predators associated with the hemlock woolly adelgid (Hemiptera: Adelgidae) in the Pacific Northwest.

The hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is causing widespread mortality of eastern hemlock, Tsuga canadensis L. Carrière, in the eastern United States. In western North America, feeding by A. tsugae results in negligible damage to western hemlock, Tsuga heterophylla (Raf.) Sargent. Host tolerance and presence of endemic predators may be contributing to the relatively low levels of injury to T. heterophylla caused by A. tsugae. Field surveys of the predator community associated with A. tsugae infestations on 116 T. heterophylla at 16 sites in Oregon and Washington were conducted every 4-6 wk from March 2005 through November 2006. Fourteen uninfested T. heterophylla were also surveyed across 5 of the 16 sites. Each sample tree was assigned an A. tsugae population score ranging from 0 to 3. Predators collected from A. tsugae-infested T. heterophylla represent 55 species in 14 families, listed in order of abundance: Derodontidae, Chamaemyiidae, Hemerobiidae, Coccinellidae, Cantharidae, Reduviidae, Miridae, Syrphidae, Chrysopidae, Coniopterygidae, Staphylinidae, Anthocoridae, Nabidae, and Raphidiidae. Laricobius nigrinus Fender (Coleoptera: Derodontidae), Leucopis argenticollis Zetterstedt (Diptera: Chamaemyiidae), and Leucopis atrifacies (Aldrich) (Chamaemyiidae) were the most abundant predators; together comprising 59% of predator specimens recovered. Relationships among predators and A. tsugae were determined through community structure analysis. The abundances of Laricobius spp. larvae, L. nigrinus adults, Leucopis spp. larvae, and L. argenticollis adults were found to be positively correlated to A. tsugae population score. Predators were most abundant when the two generations of A. tsugae eggs were present. L. argenticollis and L. atrifacies were reared on A. tsugae in the laboratory, and host records show them to feed exclusively on Adelgidae.

Parasitoids reared from predators of hemlock woolly adelgid (Hemiptera: Adelgidae), and the hymenopterous parasitoid community on western hemlock in the Pacific Northwest.

In western North America, infestations of the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), are common on orchard, ornamental, and roadside western hemlock, Tsuga heterophylla (Raf.) Sargent. However, these infestations rarely cause T. heterophylla mortality. Host tolerance and presence of endemic predators may be contributing to the relatively low levels of injury to T. heterophylla caused by A. tsugae. Field surveys of the arthropod community associated with A. tsugae infestations on 116 T. heterophylla at 16 sites in Oregon and Washington were conducted every 4-6 wk from January 2005 through November 2006. Fourteen uninfested T. heterophylla were also surveyed across 5 of the 16 sites. Immature A. tsugae predators collected in the field were brought to the laboratory for rearing. Eight species of hymenopterous parasitoids were reared from pupae of predators of A. tsugae in the laboratory. Two Pachyneuron spp. (Pteromalidae) and a Melanips sp. (Figitidae) were reared from Leucopis spp. (Diptera: Chamaemyiidae) puparia. Syrphoctonus pallipes (Gravenhorst) (Ichneumonidae), Woldstedtius flavolineatus (Gravenhorst) (Ichneumonidae), Syrphophagus sp. (Encyrtidae), and Pachyneuron albutius Walker were reared from Syrphidae (Diptera) puparia. A Helorus sp. (Heloridae) was reared from a Chrysoperla sp. (Neuroptera: Chrysopidae) cocoon. Laboratory rearing did not show any direct association between parasitoids and A. tsugae. In the field survey, a total of 509 adult parasitic Hymenoptera representing 19 families and at least 57 genera were collected from T. heterophylla. Nonparametric analysis of community structure showed Pachyneuron spp. were strongly correlated to abundance of their Leucopis spp. hosts and to A. tsugae population score in the field. The possible impact of parasitism on Leucopis spp., potential A. tsugae biological control candidates for the eastern United States, is discussed.

TM20, a gene coding for a new class of transmembrane proteins expressed in the meristematic tissues of maize.

In the course of the analysis of lachrima, a recessive, defective kernel, embryo-lethal mutation in Zea mays that alters embryo and endosperm development, a gene coding for a new class of transmembrane proteins was isolated. The mutant was produced by Ac transposon tagging, and a gene located in the insertion region of the transposon was isolated as well as the corresponding cDNA. The predicted protein contains twenty hydrophobic segments that can be grouped in five repeats formed by four segments that fulfill the criteria for membrane spanning domains, and for this reason the gene has been named TM20. The sequences of the domains in each position of each group can be aligned, indicating that TM20 is formed by a four-domain structure duplicated five times. During embryogenesis in wild-type embryos and in the growing plant, TM20 gene expression is associated with meristems.

Characterization of the sequence coding for the clathrin coat assembly protein AP17 (sigma2) associated with the plasma membrane from Zea mays and constitutive expression of its gene.

The cDNA and genomic sequences coding for the clathrin coat assembly protein AP17 (sigma2) from maize and its corresponding mRNA accumulation have been analyzed. This protein in yeast and mammals has been shown to be part of the associated protein (AP) complex of clathrin in the plasma membrane. The availability of this sequence as well as a previous AP19 in a plant allows one to propose that specific AP complexes exist in plants in the Golgi complex and in the plasma membrane. The AP17 protein is encoded in maize by a single gene, and its mRNA accumulates in all the organs studied. In the immature embryo, it displays a pattern of expression typical of constitutively expressed genes.

A new Arabidopsis nucleic-acid-binding protein gene is highly expressed in dividing cells during development.

An Arabidopsis thaliana cDNA encoding a new RNA-binding protein (RBP37) was cloned from a silique cDNA library. The predicted amino acid sequence corresponds to a RBP containing two RNA recognition motifs (RRM) and a basic domain. An affinity for nucleic acids was confirmed in binding assays using in vitro synthesised AtRBP37 protein. In situ hybridisation experiments on sections of flowers and siliques showed expression only in growing organs: gynoecium, petals, filaments and during early-embryogenesis expression is located in the embryo proper and the suspensor up to late heart stage. Expression is not detected in the embryo during maturation. This results suggests an expression pattern correlated with dividing cells.

Expression of class I O-methyltransferase in healthy and TMV-infected tobacco.

Tobacco possesses two distinct classes of O-methyltransferases (OMTs; S-adenosyl-L-methionine:o-diphenol O-methyltransferases; EC 2.1.1.6). Here we report on the cloning and the expression pattern of the class I OMT that is specifically involved in lignin biosynthesis. Near-full-length cDNAs have been isolated from tobacco libraries constructed from leaf and stem poly(A)+ RNA. Sequence analysis demonstrated that the OMT I clones derived from two different mRNA species. The two types of OMT I mRNA were reverse transcribed from total RNA and the cDNAs were amplified by polymerase chain reaction and characterized by restriction analysis. The same proportion of the two transcripts was measured in stem tissue of healthy plants and in leaves reacting hypersensitively to tobacco mosaic virus, indicating a coordinate expression of the two OMT I genes. Consistently, genomic hybridization indicated the presence of two OMT I genes in the amphidiploid genome of tobacco. The pattern of expression of OMT I genes was studied by in situ mRNA hybridization. In stem, petiole, and root tissues, OMT I genes were found to be specifically expressed in vascular cells and epidermis. In healthy leaves OMT I mRNA was only detected in vascular strands, whereas, in leaves bearing tobacco mosaic virus-induced necrotic lesions, a particularly strong accumulation of the labeling was also localized in the upper and lower epidermis.

The maize caffeic acid O-methyltransferase gene promoter is active in transgenic tobacco and maize plant tissues.

The pattern of expression directed by the promoter of the maize caffeic acid O-methyltransferase (COMT) gene was studied by histochemical and fluorometric beta-glucuronidase (GUS) analysis in transgenic maize and tobacco plants. The COMT promoter directs GUS expression to the xylem and the other tissues undergoing lignification, and it responds to wounding and to elicitors. In transgenic maize plants, expression of GUS corresponds to the pattern of expression of the endogenous COMT gene as determined by northern analysis and in situ hybridization. The pattern in transgenic tobacco plants clearly shows that the maize promoter sequence is recognized by tobacco transcriptional factors, in spite of the anatomical differences and the evolutionary distance between these two species. The results suggest that the most significant promoter signals that induce the specific expression of the lignin COMT are conserved in different species.

Molecular characterization of the gene coding for GPRP, a class of proteins rich in glycine and proline interacting with membranes in Arabidopsis thaliana.

The gene coding for a new class of proteins rich in glycine and proline (GPRP) was cloned in Arabidopsis thaliana. In the protein sequence, five amino acids - glycine, proline, alanine, tyrosine and histidine - account for 79.4% of the total composition. The protein has two different glycine-rich domains interrupted by a hydrophobic segment having a high probability of helix formation. The protein synthesized in vitro interacts with microsomes possibly through the hydrophobic domain. The gene in Arabidopsis has two introns, one in the coding region and the other one in the 5' non-coding region. The later one is 778 bp long. Homologous sequences are found in carrot, tomato and tobacco. GPRP mRNA is found in the different organs of the plant analyzed except in mature seeds and anthers, and mostly in epidermal and vascular tissues. Possible hypotheses about the function of GPRP are discussed.

Molecular cloning and pattern of expression of an alpha-L-fucosidase gene from pea seedlings.

alpha-L-Fucosidase is a cell wall protein purified from pea (Pisum sativum) epicotyls. The alpha-L-fucosidase hydrolyzes terminal fucosyl residues from oligosaccharides of plant cell wall xyloglucan. alpha-L-Fucosidase may be an important factor in plant growth regulation, as it inactivates fucose-containing xyloglucan oligosaccharides that inhibit growth of pea stem segments. The amino acid sequences of the NH2-terminal region and one internal peptide were used to design redundant oligonucleotides that were utilized as primers in a polymerase chain reaction (PCR) with cDNA, generated from pea mRNA, as the template. A specific PCR amplification product containing 357 base pairs was isolated, cloned, and sequenced. The deduced amino acid sequence included the two peptides used to design the primers for PCR plus two other peptides obtained by proteinase digestion of alpha-L-fucosidase. No sequence homology to other alpha-L-fucosidases was apparent, although the NH2-terminal region is strongly homologous to Kunitz-type trypsin inhibitors. cDNA and genomic copies were isolated and sequenced. In pea, the gene is present in two or three copies. Its mRNA is present in roots, leaves, and elongating shoots. The spatial pattern of expression of the alpha-L-fucosidase was determined by in situ hybridization.

Accumulation of cell wall hydroxyproline-rich glycoprotein mRNA is an early event in maize embryo cell differentiation.

The accumulation of the mRNA coding for a hydroxyproline-rich glycoprotein (HRGP), an abundant component of the wall from the cells of vegetative tissues, has been observed in maize embryo by in situ hybridization. The HRGP mRNA accumulates in the embryo axis and not in the scutellum and preferentially in dividing and provascular cells. The histone H4 mRNA is distributed in similar tissues but is restricted to defined groups of cells, indicating that these two gene products have a different steady-state level of accumulation during the cell cycle. The HRGP mRNA appears to be a useful marker for early formation of the vascular systems. The mRNA accumulation correlates in space and time with cells having a low content of cellulose in their walls, suggesting that the mRNA is produced in the early stages of cell wall formation before complete deposition of cellulose.

Expression of a maize cell wall hydroxyproline-rich glycoprotein gene in early leaf and root vascular differentiation.

The spatial pattern of expression for a maize gene encoding a hydroxyproline-rich glycoprotein (HRGP) was determined by in situ hybridization. During normal development of roots and leaves, the expression of the gene was transient and particularly high in regions initiating vascular elements and associated sclerenchyma. Its expression was also associated with the differentiation of vascular elements in a variety of other tissues. The gene encoded an HRGP that had been extracted from the cell walls of maize suspension culture cells and several other embryonic and post-embryonic tissues. The gene was present in one or two copies in different varieties of maize and in the related monocots teosinte and sorghum. A single gene was cloned from maize using a previously characterized HRGP cDNA clone [Stiefel et al. (1988). Plant Mol. Biol. 11, 483-493]. In addition to the coding sequences for the HRGP and an N-terminal signal sequence, the gene contained a single intron in the nontranslated 3' end.

Expression of genes for cell-wall proteins in dividing and wounded tissues ofZea mays L.

Hydroxyproline-rich glycoproteins (HRGPs) fromZea mays have been immunolocalized in the cell wall of root tip cells using ultrathin sections and antibodies ellicited against the purified protein. The accumulation of mRNA corresponding to this protein was studied using the cDNA probe. Maximum accumulation of the mRNA was found in tissues with a high proportion of dividing cells such as those in the root tip of young maize seedlings and a close relationship with cellular division was also observed in in-vitro cultures. However, the level of the mRNA in elongating tissues was minimal, as shown by studies carried out on the elongation zones of root tips and coleoptiles. The mRNA was induced by stress conditions, particularly by wounding young leaves and coleoptiles. It is concluded that in maize this group of proline-rich cell-wall proteins accumulates during cell division and not during cell elongation or differentiation, and participates in the stress-response mechanisms of the plant.

Phospholipid transfer protein: full-length cDNA and amino acid sequence in maize. Amino acid sequence homologies between plant phospholipid transfer proteins.

We have determined the primary structure of a phospholipid transfer protein (PLTP) isolated from maize seeds. This protein consists of 93 amino acids and shows internal homology originating in the repetition of (do)decapeptides. By using antibodies against maize PLTP, we have isolated from a cDNA library one positive clone (6B6) which corresponds to the incomplete nucleotide sequence. Another cDNA clone (9C2) was obtained by screening a size-selected library with 6B6. Clone 9C2 (822 base pairs) corresponds to the full-length cDNA of the phospholipid-transfer protein whose mRNA contains 0.8 kilobase. Southern blot analysis shows that the maize genome may contain several PLTP genes. In addition, the deduced amino acid sequence of clone 9C2 reveals the presence of a signal peptide. The significance of this signal peptide (27 amino acids) might be related to the function of the phospholipid-transfer protein. The amino acid sequence of maize PLTP was compared to those isolated from spinach leaves or castor bean seeds which exhibit physicochemical properties close to those of the maize protein. A high homology was observed between the three sequences. Three domains can be distinguished: a highly charged central core (around 40-60), a very hydrophobic N-terminal sequence characteristic of polypeptide-membrane interaction, and a hydrophilic C terminus. A model for plant phospholipid-transfer proteins is proposed in which the phospholipid molecule is embedded within the protein with its polar moiety interacting with the central hydrophilic core of the protein, whereas the N-terminal region plunges within the membrane in the transfer process.

Molecular cloning of cDNAs encoding a putative cell wall protein from Zea mays and immunological identification of related polypeptides.

Copy DNAs corresponding to a highly repetitive, proline-rich protein from maize have been cloned by differential screening of a coleoptile cDNA library. The deduced amino acid sequence contains a single repetitive element of carrot extensin (Ser-Pro-Pro-Pro-Pro). The related mRNAs have a defined distribution in tissues of the plant and are accumulated mainly in the coleoptile node and root tip. A peptide that corresponds to one of the repetitive elements of the protein has been synthesized and antisera have been obtained in rabbits. These antibodies react against crude preparations of coleoptile cell wall and against polypeptides extracted following the protocols described for the extraction of extensin. From these data it is concluded that the cDNAs correspond to a family of cell wall glycoproteins from maize.