Systemic acquired resistance in soybean is regulated by two proteins, Orthologous to Arabidopsis NPR1

<p>Abstract</p> <p>Background</p> <p>Systemic acquired resistance (SAR) is induced in non-inoculated leaves following infection with certain pathogenic strains. SAR is effective against many pathogens. Salicylic acid (SA) is a signaling molecule of the SAR pathway. The development of SAR is associated with the induction of pathogenesis related (<it>PR</it>) genes. Arabidopsis <it>non-expressor </it>of <it>PR1 </it>(<it>NPR1</it>) is a regulatory gene of the SA signal pathway <abbrgrp><abbr bid="B1">1</abbr><abbr bid="B2">2</abbr><abbr bid="B3">3</abbr></abbrgrp>. SAR in soybean was first reported following infection with <it>Colletotrichum trancatum </it>that causes anthracnose disease. We investigated if SAR in soybean is regulated by a pathway, similar to the one characterized in Arabidopsis.</p> <p>Results</p> <p>Pathogenesis-related gene <it>GmPR1 </it>is induced following treatment of soybean plants with the SAR inducer, 2,6-dichloroisonicotinic acid (INA) or infection with the oomycete pathogen, <it>Phytophthora sojae</it>. In <it>P. sojae</it>-infected plants, SAR was induced against the bacterial pathogen, <it>Pseudomonas syringae </it>pv. glycinea. Soybean <it>GmNPR1-1 </it>and <it>GmNPR1-2 </it>genes showed high identities to Arabidopsis <it>NPR1</it>. They showed similar expression patterns among the organs, studied in this investigation. <it>GmNPR1-1 </it>and <it>GmNPR1-2 </it>are the only soybean homologues of <it>NPR1</it>and are located in homoeologous regions. In <it>GmNPR1-1 </it>and <it>GmNPR1-2 </it>transformed Arabidopsis <it>npr1-1 </it>mutant plants, SAR markers: (i) <it>PR-1 </it>was induced following INA treatment and (ii) <it>BGL2 </it>following infection with <it>Pseudomonas syringae </it>pv. tomato (<it>Pst</it>), and SAR was induced following <it>Pst </it>infection. Of the five cysteine residues, Cys⁸², Cys¹⁵⁰, Cys¹⁵⁵, Cys¹⁶⁰, and Cys²¹⁶involved in oligomer-monomer transition in NPR1, Cys²¹⁶ in GmNPR1-1 and GmNPR1-2 proteins was substituted to Ser and Leu, respectively.</p> <p>Conclusion</p> <p>Complementation analyses in Arabidopsis <it>npr1-1 </it>mutants revealed that homoeologous <it>GmNPR1-1 </it>and <it>GmNPR1-2 </it>genes are orthologous to Arabidopsis <it>NPR1</it>. Therefore, SAR pathway in soybean is most likely regulated by <it>GmNPR1 </it>genes. Substitution of Cys²¹⁶residue, essential for oligomer-monomer transition of Arabidopsis NPR1, with Ser and Leu residues in GmNPR1-1 and GmNPR1-2, respectively, suggested that there may be differences between the regulatory mechanisms of GmNPR1 and Arabidopsis NPR proteins.</p

Coordinated spatial and temporal expression of Hox genes during embryogenesis in the acoel Convolutriloba longifissura

Background: Hox genes are critical for patterning the bilaterian anterior-posterior axis. The evolution of their clustered genomic arrangement and ancestral function has been debated since their discovery. As acoels appear to represent the sister group to the remaining Bilateria (Nephrozoa), investigating Hox gene expression will provide an insight into the ancestral features of the Hox genes in metazoan evolution. Results: We describe the expression of anterior, central and posterior class Hox genes and the ParaHox ortholog Cdx in the acoel Convolutriloba longifissura. Expression of all three Hox genes begins contemporaneously after gastrulation and then resolves into staggered domains along the anterior-posterior axis, suggesting that the spatial coordination of Hox gene expression was present in the bilaterian ancestor. After early surface ectodermal expression, the anterior and central class genes are expressed in small domains of putative neural precursor cells co-expressing ClSoxB1, suggesting an evolutionary early function of Hox genes in patterning parts of the nervous system. In contrast, the expression of the posterior Hox gene is found in all three germ layers in a much broader posterior region of the embryo. Conclusion: Our results suggest that the ancestral set of Hox genes was involved in the anteriorposterior patterning of the nervous system of the last common bilaterian ancestor and were later co-opted for patterning in diverse tissues in the bilaterian radiation. The lack of temporal colinearity of Hox expression in acoels may be due to a loss of genomic clustering in this clade or, alternatively, temporal colinearity may have arisen in conjunction with the expansion of the Hox cluster in the Nephrozoa

The involvement of photosystem II-generated H2O2 in photoinhibition

AbstractThe involvement of H2O2 generated by photosystem II (PSII) in the process of photoinhibition of thylakoids with a functional oxygen-evolving complex (OEC) was investigated. The rate of photoinhibition was decreased to the rate of loss of activity in the dark when bovine Fe-catalase was present during the photoinhibitory illumination. Photoinhibition was accelerated for both Cl−-depleted and Cl−-sufficient thylakoids when KCN was present to inhibit the thylakoid-bound Fe-catalase. We propose that these preparations become photoinhibed by reactions with H2O2 produced via oxidation of water by the Cl−-depleted OEC and by reduction of O2 at the QB site when PSII is illuminated without an electron acceptor