Soluble low-molecular-mass protein isoforms were purified from chemosensory organs (antennae, tarsi and labrum) of the desert locust Schistocerca gregaria. Five genes encoding proteins of this group were amplified by PCR from cDNAs of tarsi and sequenced. Their expression products are polypeptide chains of 109 amino acids showing 40±50% sequence identity with putative olfactory proteins from Drosophila melanogaster and Cactoblastis cactorum. Direct structural investigation on isoforms purified from chemosensory organs revealed the presence in the expression products of two of the genes cloned. Two additional protein isoforms were detected and their molecular structure exhaustively characterized. MS analysis of all isoforms demonstrated that the four cysteine residues conserved in the polypeptide chain were involved in disulfide bridges (Cys29±Cys38 and Cys57±Cys60) and indicated the absence of any additional post-translational modifications. Immunocytochemistry experiments, performed with rabbit antiserum raised against the protein isoform mixture, showed selective labelling of the outer lymph in contact sensilla of tarsi, maxillary palps and antennae. Other types of sensilla were not labelled, nor were the cuticle and dendrites of the sensory cells. No binding of radioactively labelled glucose or bicarbonate was detected, in disagreement with the hypothesis that this class of proteins is involved in the CO 2 -sensing cascade. Our experimental data suggest that the proteins described here could be involved in contact chemoreception in Orthoptera.Keywords: chemosensory proteins; contact sensilla; disulfide bridges; Schistocerca gregaria; sequence analysis.Locusts and grasshoppers are major pests in agriculture. They have a solitary and a gregarious phase, characterized by different behaviour and morphological features [1]. All crop damage is caused by individuals in the gregarious phase.In the species Schistocerca gregaria, the shift from the solitary to the gregarious phase is preceded by an associating phase, triggered by volatile aromatic compounds, such as guaiacol, veratrol and phenylacetonitrile [2]. In the gregarious phase, the same chemicals, and perhaps related structures, induce aggregation of great numbers of individuals. Under these conditions this species becomes a plague and can destroy entire crops. Therefore, it is evident that these insects rely on chemical communication and that their populations could be controlled by the use of the appropriate chemical stimuli.Despite such pressing objectives, biochemical study of the olfactory system had been limited until recently to Lepidopteran species with large antennae. In the last few years, however, molecular biology techniques have made such research feasible in small insects of wider interest, such as Drosophila melanogaster. In this paper we report the isolation of soluble low-molecularmass proteins in antennae, tarsi and labrum of S. gregaria, their complete structural characterization by combined Edman degradation/MS procedures and the cloning of...

The polymorphic barley (Hordeum vulgare) Mla locus harbors allelic race-specific resistance (R) genes to the powdery mildew fungus Blumeria graminis f sp hordei. The highly sequence-related MLA proteins contain an N-terminal coiled-coil structure, a central nucleotide binding (NB) site, a Leu-rich repeat (LRR) region, and a C-terminal non-LRR region. Using transgenic barley lines expressing epitope-tagged MLA1 and MLA6 derivatives driven by native regulatory sequences, we show a reversible and salt concentration-dependent distribution of the intracellular MLA proteins in soluble and membraneassociated pools. A posttranscriptional process directs fourfold greater accumulation of MLA1 over MLA6. Unexpectedly, in rar1 mutant plants that are compromised for MLA6 but not MLA1 resistance, the steady state level of both MLA isoforms is reduced. Furthermore, differential steady state levels of MLA1/MLA6 hybrid proteins correlate with their requirement for RAR1; the RAR1-independent hybrid protein accumulates to higher levels and the RAR1-dependent one to lower levels. Interestingly, yeast two-hybrid studies reveal that the LRR domains of RAR1-independent but not RAR1-dependent MLA isoforms interact with SGT1, a RAR1 interacting protein required for the function of many NB-LRR type R proteins. Our findings implicate the existence of a conserved mechanism to reach minimal NB-LRR R protein thresholds that are needed to trigger effective resistance responses.

Symptoms of sugarcane orange rust were observed on July 17, 2008 on sugarcane cvs. Mex 57-1285, Mex 61-230, and Co 301 (a clone received in Mexico in 1953) at the Centro de Investigación y Desarrollo de la Caña de Azúcar en Tuxtla Chico, Chiapas, Mexico. In El Salvador, from August 2008 through January 2009, rust symptoms were observed on cv. CP 72-2086 (previously resistant to brown rust caused by Puccinia melanocephala Syd. & P. Syd.) in 117 dispersed sugarcane-production fields in various localities of El Salvador. Likewise, rust symptoms were first observed on sugarcane cv. SP 74-8355 (more than 25% severity and considered resistant to brown rust) at Natá, Coclé Province in Panama from January to February 2008. Dried herbarium leaf samples of sugarcane rust-infected leaves collected in El Salvador and Mexico were sent to the ARS, USDA Systematic Mycology and Microbiology Laboratory in Beltsville MD for identification. Panamanian samples were collected similarly and analyzed at the CALESA Biotechnology Laboratory. Morphological features of uredinial lesions and urediniospores were distinct from those of P. melanocephala and consistent with P. kuehnii E. J. Butler observed previously on specimens from Florida, Guatemala, Costa Rica, and Nicaragua (1–3). Analysis of the ITS1, 5.8S, and ITS2 and 28S large subunit rDNA sequences of the rust on infected cvs. Mex 57-1285, Mex 61-230, and Co 301 (BPI 878930, 879139, and 879140; GenBank Accession Nos. GO283006, GO283004, and GO283005, respectively) from Mexico and cv. CP 72-2086 from three locations in El Salvador (BPI 879135, 879136, and 879137; GenBank Accession Nos. GO283009, GO283007, and GO283008, respectively) all confirmed the identification of P. kuehnii. Similar analysis of the ITS1, 5.8S, and ITS2 rDNA sequence for the rust infecting cv. SP 74-8355 (GenBank Accession No. GO281584) confirmed the identification of P. kuehnii in Panama. To our knowledge, this is the first report of P. kuehnii causing orange rust disease of sugarcane in El Salvador, Mexico, and Panama. These findings also confirm the wider distribution of orange rust in the Western Hemisphere. References: (1) E. Chavarria et al. Plant Dis. 93:425, 2009. (2) J. C. Comstock et al. Plant Dis. 92:175, 2008. (3) W. Ovalle et al. Plant Dis. 92:973, 2008.

We have isolated PcGA3ox1, a cDNA clone from developing runner bean (Phaseolus coccineus) seeds that shows significant amino acid homology with the gibberellin (GA) 3-oxidases. A recombinant fusion protein of PcGA3ox1 converted GA20 and GA9 to GA1 and GA4, respectively. In situ hybridization results showed that transcripts of this gene accumulate specifically within the suspensor of globular-stage embryos. PcGA3ox1 mRNA begins to accumulate in the epidermal cells of the embryo proper and is also detectable in the endosperm during the transition from globular- to heart-stage embryos. PcGA3ox1 transcripts were localized exclusively in the cotyledons from the early cotyledonary stage up to the cotyledonary stage. Transcripts of the previously cloned GA 2-oxidase (PcGA2ox1) from developing seeds of runner bean were found primarily within the suspensor neck region from the late globular stage up to the heart stage. PcGA2ox1 mRNA was detectable in the whole suspensor from the early cotyledonary stage, and was found in the inner layer of integuments at the cotyledonary stage. Soluble enzyme preparations made from suspensors and embryos at two stages of embryogenesis (the heart and cotyledonary stages) were incubated with [14C]GA20 and [14C]GA1. Only young suspensor preparations converted GA20 to GA1 and GA5. Both suspensor preparations converted GA1 to GA8. Both embryo preparations converted GA20 to GA1, but were unable to convert GA1 to GA8.