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Parasitic nematodes are a major threat to global food security, particularly as the world amasses 10 billion people amidst limited arable land. Most traditional nematicides have been banned due to poor nematode-selectivity, leaving farmers with inadequate controls. Here, we use the model nematode Caenorhabditis elegans to identify a family of selective imidazothiazole nematicides, called selectivins, that undergo cytochrome p450-dependent bioactivation exclusively in nematodes. At low parts-per-million concentrations, selectivins perform comparably well with commercial nematicides to control root infection by Meloidogyne incognita – the world’s most destructive plant-parasitic nematode. Tests against a wide range of phylogenetically diverse non-target systems demonstrate that selectivins are more nematode-selective than nearly all marketed nematicides. Thus, selectivins are first-in-class bioactivated nematode controls that provide efficacy as well as much-needed nematode selectivity.

Tea-oil camellia (Camellia oleifera) is grown for tea seed oil production, with tea seed cake produced as a byproduct. Rather than disposing of the cake, agricultural uses increase the value of oil production. Constituents of C. oleifera are also utilized for traditional Chinese medicine, as are compounds produced by tree peony roots. Consequently, the unused C. oleifera cake, and stems from two tree peony species, Paeonia rockii and Paeonia suffruticosa, were studied for compounds antagonistic to soybean cyst nematode (Heterodera glycines) and root-knot nematode (Meloidogyne incognita). Extracts from C. oleifera cake and P. rockii stems suppressed hatch and were nematotoxic to second-stage juveniles (J2) of both nematode species. P. rockii extracts were more effective than P. suffruticosa extracts for decreasing M. incognita hatch and J2 viability. In greenhouse trials with soybean (Glycine max ‘Essex’), powdered C. oleifera cake applied as a soil amendment suppressed H. glycines cysts/g root by up to 66% compared with nonamended controls. These results indicate that the extracts and cake contain compounds active against H. glycines and M. incognita, with activity varying between the two Paeonia species. C. oleifera tea seed cake, and constituents of the cake or of P. rockii, are candidates for further studies on management of these nematodes.

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Agrobacterium-mediated transformation of plants has enhanced our ability to progress more rapidly in plant genetic engineering. Development of binary vectors for Agrobacterium has played a major role in advancing plant biology. Here, we report new features added to the Gateway-compatible vector pGWB533 for promoter testing with the reporter gene encoding β-glucuronidase (GUS). The original vector contains the spectinomycin/streptomycin adenylyltransferase (aadA) gene for bacterial selection and the hygromycin phosphotransferase gene (hpt) for transformed plant selection. However, some bacterial strains used to transform plants, such as Agrobacterium rhizogenes strain K599, have elevated tolerance to spectinomycin and streptomycin, thus making bacterial selection of pGWB533 inefficient. Although pGWB533 confers chemical selection for transgenic plants using hygromycin resistance, the plasmid has no visual marker that enables visual selection of transformed plants or transgenic tissue. In this regard, adding a gene to constitutively express green fluorescent protein (eGFP) makes it easier to visually select the transformed tissue and trim out the non-transformed. In this report we describe a series of vectors, pJan25S (NCBI: KC416200), pJan25T (NCBI: KC416201) and pJan25X (NCBI: KC416202), that are enhancements of pGWB533 for promoter testing. All three vectors contain the gene encoding eGFP as a visual marker for transformed tissue. However, in pJan25S and pJan25T, eGFP is controlled by the rolD promoter for root-specific expression, while in pJan25X it is controlled by the CaMV35S promoter for constitutive expression in all plant tissues. Spectinomycin and streptomycin resistance remains in pJan25S for bacterial selection; however, pJan25T and pJan25X contain the gene encoding tetracycline resistance (tet) for bacterial selection. These changes resulted in enhanced vectors with better visual and chemical selection that should have broad application in promoter studies.

During pathogen attack, the host plant induces genes to ward off the pathogen while the pathogen often produces effector proteins to increase susceptibility of the host. Gene expression studies of syncytia formed in soybean root by soybean cyst nematode (Heterodera glycines) identified many genes altered in expression in resistant and susceptible roots. However, it is difficult to assess the role and impact of these genes on resistance using gene expression patterns alone. We selected 100 soybean genes from published microarray studies and individually overexpressed them in soybean roots to determine their impact on cyst nematode development. Nine genes reduced the number of mature females by more than 50 % when overexpressed, including genes encoding ascorbate peroxidase, β-1,4-endoglucanase, short chain dehydrogenase, lipase, DREPP membrane protein, calmodulin, and three proteins of unknown function. One gene encoding a serine hydroxymethyltransferase decreased the number of mature cyst nematode females by 45 % and is located at the Rhg4 locus. Four genes increased the number of mature cyst nematode females by more than 200 %, while thirteen others increased the number of mature cyst nematode females by more than 150 %. Our data support a role for auxin and ethylene in susceptibility of soybean to cyst nematodes. These studies highlight the contrasting gene sets induced by host and nematode during infection and provide new insights into the interactions between host and pathogen at the molecular level. Overexpression of some of these genes result in a greater decrease in the number of cysts formed than recognized soybean cyst nematode resistance loci.

2-DE reference maps of Heterodera glycines were constructed. After in-gel digestion with trypsin, 803 spots representing 426 proteins were subsequently identified by LC-MS/MS. Proteins with annotated function were further categorized by Gene Ontology. The results showed that proteins involved in metabolic, developmental and biological regulation processes were the most abundant.

Vetiver, a nonhost grass for certain nematodes, was studied for the production of compounds active against the southern root-knot nematode, Meloidogyne incognita. In laboratory assays studying the effects on second-stage juvenile (J2) activity and viability, crude vetiver root and shoot extracts were nematotoxic, resulting in 40% to 70% J2 mortality, and were also repellent to J2. Vetiver oil did not exhibit activity against J2 in these assays. Gas chromatography-mass spectrometry analyses of three crude vetiver root ethanol extracts and a commercial vetiver oil determined that two of the major components in each sample were the sesquiterpene acid 3,3,8,8-tetramethyltricyclo[5.1.0.0(2,4)]oct-5-ene-5-propanoic acid and the sesquiterpene alcohol 6-isopropenyl-4,8a-dimethyl-1,2,3,5,6,7,8,8a-octahydronaphthalen-2-ol. The acid was present in higher amounts in the extracts than in the oil. These studies demonstrating nematotoxicity and repellency of vetiver-derived compounds to M. incognita suggest that plant chemistry plays a role in the nonhost status of vetiver to root-knot nematodes, and that the chemical constituents of vetiver may be useful for suppressing nematode populations in the soil.

Syncytial cells in soybean (Glycine max cultivar [cv.] Peking) roots infected by incompatible and compatible populations of soybean cyst nematode (SCN [Heterodera glycines]) were collected using laser capture microdissection (LCM). Gene transcript abundance was assayed using Affymetrix® soybean GeneChips®, each containing 37,744 probe sets. Our analyses identified differentially expressed genes in syncytial cells that are not differentially expressed in the whole root analyses. Therefore, our results show that the mass of transcriptional activity occurring in the whole root is obscuring identification of transcriptional events occurring within syncytial cells. In syncytial cells from incompatible roots at three dpi, genes encoding lipoxygenase (LOX), heat shock protein (HSP) 70, superoxidase dismutase (SOD) were elevated almost tenfold or more, while genes encoding several transcription factors and DNA binding proteins were also elevated, albeit at lower levels. In syncytial cells formed during the compatible interaction at three dpi, genes encoding prohibitin, the epsilon chain of ATP synthase, allene oxide cyclase and annexin were more abundant. By 8 days, several genes of unknown function and genes encoding a germin-like protein, peroxidase, LOX, GAPDH, 3-deoxy-D-arabino-heptolosonate 7-phosphate synthase, ATP synthase and a thioesterase were abundantly expressed. These observations suggest that gene expression is different in syncytial cells as compared to whole roots infected with nematodes. Our observations also show that gene expression is different between syncytial cells that were isolated from incompatible and compatible roots and that gene expression is changing over the course of syncytial cell development as it matures into a functional feeding site.

Summary Plant endo-β-1,4-glucanases (EGases) include cell wall-modifying enzymes that are involved in nematode-induced growth of syncytia (feeding structures) in nematode-infected roots. EGases in the α- and β-subfamilies contain signal peptides and are secreted, whereas those in the γ-subfamily have a membrane-anchoring domain and are not secreted. The Arabidopsis α-EGase At1g48930, designated as AtCel6, is known to be down-regulated by beet cyst nematode (Heterodera schachtii) in Arabidopsis roots, whereas another α-EGase, AtCel2, is up-regulated. Here, we report that the ectopic expression of AtCel6 in soybean roots reduces susceptibility to both soybean cyst nematode (SCN; Heterodera glycines) and root knot nematode (Meloidogyne incognita). Suppression of GmCel7, the soybean homologue of AtCel2, in soybean roots also reduces the susceptibility to SCN. In contrast, in studies on two γ-EGases, both ectopic expression of AtKOR2 in soybean roots and suppression of the soybean homologue of AtKOR3 had no significant effect on SCN parasitism. Our results suggest that secreted α-EGases are likely to be more useful than membrane-bound γ-EGases in the development of an SCN-resistant soybean through gene manipulation. Furthermore, this study provides evidence that Arabidopsis shares molecular events of cyst nematode parasitism with soybean, and confirms the suitability of the Arabidopsis–H. schachtii interaction as a model for the soybean–H. glycines pathosystem.

The soybean [Glycine max (L.) Merr.] expressed sequence tagged (EST) database is growing rapidly and promises to be a valuable resource for discovering agronomically important genes. Genetic maps featuring cDNA clones of known sequence and functiona re important because association of genes with phenotypes will increase understanding of the molecular mechanisms affecting valuable agronomic traits. Our objective is to place sequenced cDNA (EST) and genomic clones on an anchored soybean genetic map. The genetic mapping of these markers was conducted by standard restriction fragment length polymorphism (RFLP) techniques with an F 2 population of 149 individuals derived from a cross between two publicly available soybean genotypes cv. Noir I (PI 290136) and BARC-2 (Rj 4 ) (PI 547895). DNA sequences of mapped EST and genomic clones were compared with accessions in GenBank, and significant sequence similarities are reported. The ESTs were more likely than the genomic clones to have a significant similarity to a GenBank accession. Because the objective was to map ESTs and sequenced genomic clones, only the 24 linkage groups (1200 cM) containing the 39 mapped EST and sequenced genomic clone markers plus the four phenotypic traits root fluorescence (Fr 2 ), seed coat color (I), flower color (W 1 ) and nodulation response (Rj 4 ) were presented. Amplified fragment length polymorphism (AFLP) and random amplified polymorphic DNA (RAPD) markers were added to increase marker density. Simple sequence repeat (SSR) markers were included to align this map with other soybean maps. The population has been further advanced to develop a F 8:2 recombinant inbred line population available to researchers interested in associating the mapped cDNAs with quantitatively inherited traits.

The restriction fragment length polymorphism (RFLP) clone pBLT65 is a 450-nt soybean cDNA encoding a portion of the bifunctional enzyme aspartokinase-homoserine dehydrogenase (AK-HSDH). pBLT65 maps within 3.5 cM of the i locus, conferring a pigmented seed coat, on linkage group A; hence, it is closely linked to the Rhg 4 locus conferring resistance to race 3 of the soybean cyst nematode. From this useful RFLP we developed a PCR reaction yielding polymorphic bands for use in marker-assisted breeding programs to select progeny containing the Rhg 4 allele. The polymorphic bands were sequenced to determine the cause of the polymorphisms. Using primers 548 and 563, PCR amplification of DNA from the soybean cultivar Peking (Rhg 4 ) yielded three DNA fragments, 1a (1160 bp), 1b (1146 bp) and 3 (996 bp). Amplification of DNA from the cultivar Kent (rhg 4) yielded DNA fragments 2 (1020 bp), 3 (996 bp) and 4 (960 bp). Fragments 1a, 1b, 2 and 4 were also polymorphic between the soybean lines PI 290136 and BARC-2(Rj 4 ). A segregating population of 80 F2 and F3 plants derived from the cross PI 290136×BARC-2 (Rj 4 ) was used to confirm the map position of the PCR polymorphisms near the i locus, and hence the Rhg 4 locus on linkage group A. The nucleotide sequences of fragments 1b, 3 and 4 were determined. Large and small deletions in the intronic region were responsible for the size differences of the different fragments, whereas the exon was well conserved.

Three different DNA mapping techniques—RFLP, RAPD and AFLP—were used on identical soybean germplasm to compare their ability to identify markers in the development of a genetic linkage map. Polymorphisms present in fourteen different soybean cultivars were demonstrated using all three techniques. AFLP, a novel PCR-based technique, was able to identify multiple polymorphic bands in a denaturing gel using 60 of 64 primer pairs tested. AFLP relies on primers designed in part on sequences for endonuclease restriction sites and on three selective nucleotides. The 60 diagnostic primer pairs tested for AFLP analysis each distinguished on average six polymorphic bands. Using specific primers designed for soybean fromEco RI andMse I restriction site sequences and three selective nucleotides, as many as 12 polymorphic bands per primer could be obtained with AFLP techniques. Only 35% of the RAPD reactions identified a polymorphic band using the same soybean cultivars, and in those positive reactions, typically only one or two polymorphic bands per gel were found. Identification of polymorphic bands using RFLP techniques was the most cumbersome, because Southern blotting and probe hybridization were required. Over 50% of the soybean RFLP probes examined failed to distinguish even a single polymorphic band, and the RFLP probes that did distinguish polymorphic bands seldom identified more than one polymorphic band. We conclude that, among the three techniques tested, AFLP is the most useful.

Background. A comparative microarray investigation was done using detection call methodology (DCM) and differential expression analyses. The goal was to identify genes found in specific cell populations that were eliminated by differential expression analysis due to the nature of differential expression methods. Laser capture microdissection (LCM) was used to isolate nearly homogeneous populations of plant root cells.Results. The analyses identified the presence of 13,291 transcripts between the 4 different sample types. The transcripts filtered down into a total of 6,267 that were detected as being present in one or more sample types. A comparative analysis of DCM and differential expression methods showed a group of genes that were not differentially expressed, but were expressed at detectable amounts within specific cell types.Conclusion. The DCM has identified patterns of gene expression not shown by differential expression analyses. DCM has identified genes that are possibly cell-type specific and/or involved in important aspects of plant nematode interactions during the resistance response, revealing the uniqueness of a particular cell population at a particular point during its differentiation process.

We have conducted an extensive linker substitution analysis of the polyadenylation signal from a pea rbcS gene. From these studies, we can identify at least two, and perhaps three, distinct classes of cis element involved in mRNA 3' end formation in this gene. One of these, termed the far-upstream element, is located between 60 and 120 nt upstream from its associated polyadenylation sites and appears to be largely composed of a series of UG motifs. A second, termed the near-upstream element, is more proximate to poly(A) sites and may be functionally analogous to the mammalian polyadenylation signal AAUAAA, even though the actual sequences involved may not be AAUAAA. The third possible class is the putative cleavage and polyadenylation site itself. We find that the rbcS-E9 far-upstream element can replace the analogous element in another plant polyadenylation signal, that from cauliflower mosaic virus, and that one near-upstream element can function with either of two poly(A) sites. Thus, these different cis elements are largely interchangeable. Our studies indicate that a cellular plant gene possesses upstream elements distinct from AAUAAA that are involved in mRNA 3' end formation and that plant genes probably have modular, multicomponent polyadenylation signals.

We have characterized the polyadenylation signal from the octopine synthase (ocs) gene. This signal directs mRNA 3' end formation at a number of distinct sites. A combination of deletion and linker-substitution analyses revealed that each of these sites is controlled by multiple upstream sequence elements. Upstream sequences relatively far (greater than 80 nt) from the ocs poly[A] sites were found to be needed for functioning of these sites. Upstream sequences nearer to poly [A] sites were also found to be involved in mRNA 3' end formation in the ocs gene. In addition, a set of novel elements that mediates 3' end choice was uncovered by deletion analysis of sequences downstream from the ocs polyadenylation sites. Our experiments indicate mRNA 3' end formation in the ocs is controlled by a complex series of cis-acting signals, and suggest that the process of mRNA 3' end formation might be linked to transcription termination.

Host-mediated (hm) expression of parasite genes as tandem inverted repeats was investigated as a means to abrogate the formation of mature Heterodera glycines (soybean cyst nematode) female cysts during its infection of Glycine max (soybean). A Gateway®-compatible hm plant transformation system was developed specifically for these experiments in G. max. Three steps then were taken to identify H. glycines candidate genes. First, a pool of 150 highly conserved H. glycines homologs of genes having lethal mutant phenotypes or phenocopies from the free living nematode Caenorhabditis elegans were identified. Second, annotation of those 150 genes on the Affymetrix® soybean GeneChip® allowed for the identification of a subset of 131 genes whose expression could be monitored during the parasitic phase of the H. glycines life cycle. Third, a microarray analyses identified a core set of 32 genes with induced expression (>2.0-fold, log base 2) during the parasitic stages of infection. H. glycines homologs of small ribosomal protein 3a and 4 (Hg-rps-3a [accession number CB379877] and Hg-rps-4 [accession number CB278739]), synaptobrevin (Hg-snb-1 [accession number BF014436]) and a spliceosomal SR protein (Hg-spk-1 [accession number BI451523.1]) were tested for functionality in hm expression studies. Effects on H. glycines development were observed 8 days after infection. Experiments demonstrated that 81–93% fewer females developed on transgenic roots containing the genes engineered as tandem inverted repeats. The effect resembles RNA interference. The methodology has been used here as an alternative approach to engineer resistance to H. glycines.

The development of an infection in soybean [Glycine max L. cultivar (cv.) Peking] roots by incompatible (I) and compatible (C) populations of soybean cyst nematode (SCN) (Heterodera glycines) was assayed using an Affymetrix® soybean GeneChip®. This time-course microarray analysis, using 37,744 probe sets, measured transcript abundance during I and C. These analyses reveal that infection by individual I and C H. glycines populations influence the transcription of G. max genes differently. A substantial difference in gene expression is present between I and C at 12 h post infection. Thus, G. max can differentiate between I and C nematode populations even before they have begun to select their feeding sites. The microarray analysis identified genes induced earlier in infection during I than C. MA also identified amplitude differences in transcript abundance between I and C reactions. Some of the probe sets measuring increased transcript levels during I represented no apical meristem (NAM) and WRKY transcription factors as well as NBS-LRR kinases. Later during I, heat shock protein (HSPs) probe sets (i.e. HSP90, HSP70, ClpB/HSP101) measured increased transcript abundance. These results demonstrate that G. max roots respond very differently to the different H. glycines races even before their feeding site selection has occurred. The ability of G. max to engage an I reaction, thus, appears to be dependent on the ability of root cells to recognize the different races of H. glycines because these experiments were conducted in the identical G. max genetic background.

Background Heterodera glycines (soybean cyst nematode [SCN]), the major pathogen of Glycine max (soybean), undergoes muscle degradation (sarcopenia) as it becomes sedentary inside the root. Many genes encoding muscular and neuromuscular components belong to the uncoordinated (unc) family of genes originally identified in Caenorhabditis elegans. Previously, we reported a substantial decrease in transcript abundance for Hg-unc-87, the H. glycines homolog of unc-87 (calponin) during the adult sedentary phase of SCN. These observations implied that changes in the expression of specific muscle genes occurred during sarcopenia. Results We developed a bioinformatics database that compares expressed sequence tag (est) and genomic data of C . e legans and H . g lycines (CeHg database). We identify H. glycines homologs of C. elegans unc genes whose protein products are involved in muscle composition and regulation. RT-PCR reveals the transcript abundance of H. glycines unc homologs at mobile and sedentary stages of its lifecycle. A prominent reduction in transcript abundance occurs in samples from sedentary nematodes for homologs of actin, unc-60B (cofilin), unc-89, unc-15 (paromyosin), unc-27 (troponin I), unc-54 (myosin), and the potassium channel unc-110 (twk-18). Less reduction is observed for the focal adhesion complex gene Hg-unc-97. Conclusion The CeHg bioinformatics database is shown to be useful in identifying homologs of genes whose protein products perform roles in specific aspects of H. glycines muscle biology. Our bioinformatics comparison of C. elegans and H. glycines genomic data and our Hg-unc-87 expression experiments demonstrate that the transcript abundance of specific H. glycines homologs of muscle gene decreases as the nematode becomes sedentary inside the root during its parasitic feeding stages.

Changes in gene expression within roots of Glycine max (soybean), cv. Kent, susceptible to infection by Heterodera glycines (the soybean cyst nematode [SCN]), at 6, 12, and 24 h, and 2, 4, 6, and 8 days post-inoculation were monitored using microarrays containing more than 6,000 cDNA inserts. Replicate, independent biological samples were examined at each time point. Gene expression was analyzed statistically using T-tests, ANOVA, clustering algorithms, and online analytical processing (OLAP). These analyses allow the user to query the data in several ways without importing the data into third-party software. RT-PCR confirmed that WRKY6 transcription factor, trehalose phosphate synthase, EIF4a, Skp1, and CLB1 were differentially induced across most time-points. Other genes induced across most timepoints included lipoxygenase, calmodulin, phospholipase C, metallothionein-like protein, and chalcone reductase. RT-PCR demonstrated enhanced expression during the first 12 h of infection for Kunitz trypsin inhibitor and sucrose synthase. The stress-related gene, SAM-22, phospholipase D and 12-oxophytodienoate reductase were also induced at the early time-points. At 6 and 8 dpi there was an abundance of transcripts expressed that encoded genes involved in transcription and protein synthesis. Some of those genes included ribosomal proteins, and initiation and elongation factors. Several genes involved in carbon metabolism and transport were also more abundant. Those genes included glyceraldehyde 3-phosphate dehydrogenase, fructose-bisphosphate aldolase and sucrose synthase. These results identified specific changes in gene transcript levels triggered by infection of susceptible soybean roots by SCN.

Background Extensive studies using the model system Arabidopsis thaliana to elucidate plant defense signaling and pathway networks indicate that salicylic acid (SA) is the key hormone triggering the plant defense response against biotrophic and hemi-biotrophic pathogens, while jasmonic acid (JA) and derivatives are critical to the defense response against necrotrophic pathogens. Several reports demonstrate that SA limits nematode reproduction. Results Here we translate knowledge gained from studies using Arabidopsis to soybean. The ability of thirty-one Arabidopsis genes encoding important components of SA and JA synthesis and signaling in conferring resistance to soybean cyst nematode (SCN: Heterodera glycines) are investigated. We demonstrate that overexpression of three of thirty-one Arabidoposis genes in transgenic soybean roots of composite plants decreased the number of cysts formed by SCN to less than 50% of those found on control roots, namely AtNPR1(33%), AtTGA2 (38%), and AtPR-5 (38%). Three additional Arabidopsis genes decreased the number of SCN cysts by 40% or more: AtACBP3 (53% of the control value), AtACD2 (55%), and AtCM-3 (57%). Other genes having less or no effect included AtEDS5 (77%), AtNDR1 (82%), AtEDS1 (107%), and AtPR-1 (80%), as compared to control. Overexpression of AtDND1 greatly increased susceptibility as indicated by a large increase in the number of SCN cysts (175% of control). Conclusions Knowledge of the pathogen defense system gained from studies of the model system, Arabidopsis, can be directly translated to soybean through direct overexpression of Arabidopsis genes. When the genes, AtNPR1, AtGA2, and AtPR-5, encoding specific components involved in SA regulation, synthesis, and signaling, are overexpressed in soybean roots, resistance to SCN is enhanced. This demonstrates functional compatibility of some Arabidopsis genes with soybean and identifies genes that may be used to engineer resistance to nematodes.

Journal of Plant Registrations, Vol. 1, No. 2, September 2007 97 ‘M iniMax’ soybean [Glycine max (L.) Merr.] (Reg. No. CV-489, PI 643148) was developed by the USDA-ARS at Beltsville, MD. It was released on April 13, 2006 because of its small stature, early maturity date, and small seed size, to allow more plants to be grown and to mature in a smaller space than other soybean cultivars (Fig. 1). It is intended for researchers with limited space who desire high-density planting and as a basic laboratory model for soybean genomics, biochemical, plant disease and physiological studies. MiniMax is derived from an F9 plant from the cross [‘AC Colombe’ × PI548240 (‘T263’)] × PI548650 ‘Nattosan’. AC Colombe is a cultivar developed for the Asian natto soyfood market (Cober et al., 2001). Nattosan was developed at the Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario Canada (Zarkadas et al., 1997). AC Colombe and Nattosan are Maturity Group 00, while T263 is Maturity Group I and is a donor of df5df5 (Palmer 1977, 1984). The cross from which MiniMax originated was made in the summer of 1998 at Beltsville, MD. MiniMax was advanced by pedigree inbreeding with selection for early maturity, small stature, and small seed size in the fi eld and greenhouse at Beltsville, MD. MiniMax was planted in the fi eld June fi rst at Beltsville, MD (approx. 39° North latitude) matured in 73 to 85 d with an average plant height of 22 cm. Plants were also grown in the greenhouse in 16 h light/8 h dark for the fi rst 16 d, then at 12 h light/12h dark to initiate fl owering, which began at 23 to 27 d. The temperature was maintained between 72 and 80o F during the day and 72 to 75o F at night. Natural greenhouse lighting was supplemented with sodium vapor lights during winter months. Dry brown pods can be harvested at 9 to 11 wk after planting. In the greenhouse the small seed averaged about 5.1 g/100−1 seeds and 14 seeds per plant in the summer. MiniMax has purple fl owers, brown pods, gray pubescence and produces seeds with a yellow seed coat and Registration of ‘MiniMax’ Soybean

We have characterized the upstream nucleotide sequences involved in mRNA 3'-end formation in the 3' regions of the cauliflower mosaic virus (CaMV) 19S/35S transcription unit and a pea gene encoding ribulose-1,5-bisphosphate carboxylase small subunit (rbcS). Sequences between 57 bases and 181 bases upstream from the CaMV polyadenylation site were required for efficient polyadenylation at this site. In addition, an AAUAAA sequence located 13 bases to 18 bases upstream from this site was also important for efficient mRNA 3'-end formation. An element located between 60 bases and 137 bases upstream from the poly(A) addition sites in a pea rbcS gene was needed for functioning of these sites. The CaMV -181/-57 and rbcS -137/-60 elements were different in location and sequence composition from upstream sequences needed for polyadenylation in mammalian genes, but resembled the signals that direct mRNA 3'-end formation in yeast. However, the role of the AAUAAA motif in 3'-end formation in the CaMV 3' region was reminiscent of mRNA polyadenylation in animals. We suggest that multiple elements are involved in mRNA 3'-end formation in plants, and that interactions of different components of the plant polyadenylation apparatus with their respective sequence elements and with each other are needed for efficient mRNA 3'-end formation.

The polyadenylation signal of a pea gene for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcS) has been analyzed by deletion mutagenesis and Ti plasmid-mediated gene transfer. Sequences between 6 and 137 bases upstream from the normal polyadenylation sites in this gene (bases −6 to −137) are required for functioning of these sites. In addition, bases −111 to −235 can affect 3′ end formation by altering the pattern of 3′ termini seen in various transcription units. Sequences between 37 and 95 bases upstream from a cryptic polyadenylation site in this gene [A. G. Hunt, DNA 7: 329–336 (1988)] are necessary for mRNA 3′ end formation at this site. At least two different parts of the 3′ region of this rbcS gene can serve as a downstream element for polyadenylation at the normal poly(A) addition sites in this gene. Our studies indicate that: 1. the upstream sequences required for polyadenylation in plants are different from those defined in mammalian RNA polymerase II transcription units; 2. sequences 100 or more bases upstream and downstream from poly(A) addition sites in this gene can affect poly(A) addition site choice; and 3. there are apparently redundant downstream elements for polyadenylation in this gene.

Background The gene encoding PAD4 (PHYTOALEXIN-DEFICIENT4) is required in Arabidopsis for expression of several genes involved in the defense response to Pseudomonas syringae pv. maculicola. AtPAD4 (Arabidopsis thaliana PAD4) encodes a lipase-like protein that plays a regulatory role mediating salicylic acid signaling. Results We expressed the gene encoding AtPAD4 in soybean roots of composite plants to test the ability of AtPAD4 to deter plant parasitic nematode development. The transformed roots were challenged with two different plant parasitic nematode genera represented by soybean cyst nematode (SCN; Heterodera glycines) and root-knot nematode (RKN; Meloidogyne incognita). Expression of AtPAD4 in soybean roots decreased the number of mature SCN females 35 days after inoculation by 68 percent. Similarly, soybean roots expressing AtPAD4 exhibited 77 percent fewer galls when challenged with RKN. Conclusions Our experiments show that AtPAD4 can be used in an economically important crop, soybean, to provide a measure of resistance to two different genera of nematodes.