BackgroundRice blast disease is one of the most destructive diseases of rice worldwide. We previously cloned the rice blast resistance gene Pid2, which encodes a transmembrane receptor-like kinase containing an extracellular B-lectin domain and an intracellular serine/threonine kinase domain. However, little is known about Pid2-mediated signaling.ResultsHere we report the functional characterization of the U-box/ARM repeat protein OsPUB15 as one of the PID2-binding proteins. We found that OsPUB15 physically interacted with the kinase domain of PID2 (PID2K) in vitro and in vivo and the ARM repeat domain of OsPUB15 was essential for the interaction. In vitro biochemical assays indicated that PID2K possessed kinase activity and was able to phosphorylate OsPUB15. We also found that the phosphorylated form of OsPUB15 possessed E3 ligase activity. Expression pattern analyses revealed that OsPUB15 was constitutively expressed and its encoded protein OsPUB15 was localized in cytosol. Transgenic rice plants over-expressing OsPUB15 at early stage displayed cell death lesions spontaneously in association with a constitutive activation of plant basal defense responses, including excessive accumulation of hydrogen peroxide, up-regulated expression of pathogenesis-related genes and enhanced resistance to blast strains. We also observed that, along with plant growth, the cell death lesions kept spreading over the whole seedlings quickly resulting in a seedling lethal phenotype.ConclusionsThese results reveal that the E3 ligase OsPUB15 interacts directly with the receptor-like kinase PID2 and regulates plant cell death and blast disease resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0442-4) contains supplementary material, which is available to authorized users.

International audienceVarious organic constituents extracted from wheat and from soil organic matter have been analyzed for their carbon content, their absolute concentration and their stable carbon isotope ratios. Most organic subfractions from plants, or soil, are 13C-depleted by up to 9.4‰ relative to bulk organic matter, mainly as a result of their higher lipid content. Furthermore, soil organic constituents are unexpectedly 13C-enriched by +1.5‰ to +4.3‰ relative to homologous plant constituents. Indeed, the selective preservation of plant lignin and lipids, following incorporation into the soil biomass, should have led to the accumulation of 13C-depleted compounds. Hence, these results favour the in situ formation of soil organic matter either by recondensation of small molecules or by selective preservation of biopolymers from soil microorganisms

Much attention has been paid to improving soil fertility with organic matter (OM) application, which not only deals with organic wastes and protects the environment, but also maintains soil fertility and increases crop yields. Much research has also been on the effects of OM applications on the soil's physical, chemical and biological properties, but relatively less attention has been spent on humic substance (HS). In order to clarify the mechanism of improving soil fertility by applying OM, we analysed the changes of structural characteristics of humic acid (HA) from OM applications to soils by 13 C-NMR, chemical analysis, thermal analysis, optical properties, IR and fluorescence spectroscopy. Samples of a brown soil (Paleudalf) and a paddy soil (an anthropogenic soil originating from Udifluvents) were collected from the plough layer of the long-term field experiment at Shenyang Agricultural University and Liaoning Provincial Alkali-Saline Soil Institute, respectively. Both field experiments included three treatments each: (i) brown soil, zero-treatment (CK br ) and two pig manure (PM) applications (O 1 and O 2 ) at annual rates of 0.9 t ha À1 and 1.8 t ha À1 of organic carbon, respectively; and (ii) paddy soil, zero-treatment (CK pad ), pig manure (O p ) and rice straw (O r ) at annual rates of 2.62 t ha À1 and 1.43 t ha À1 of organic carbon, respectively. An incubation experiment was also carried out to test the field experiment on the brown soil, namely four treatments: zero-treatment (CK c ), and three pig manure applications at rates of 30 g kg À1 (C 1 ), 50 g kg À1 (C 2 ) and 70 g kg À1 (C 3 ), respectively. The total incubation was 180 days. The results indicated that number-average molecular weights (M n ), total acidity, aromaticity, excitation maximum wavelength (l Exmax ), and the heat ratio of the high to moderate temperature exothermic regions (H 3 /H 2 ) of the HA all decreased after OM application. The degree of activation (AD), the absorption intensity ratio of 2920 cm À1 to 1720 cm À1 in infrared spectra (IR 2920/1720 ), alkyl C and O-alkyl C of the HA increased. The HA structure tended to become simpler and more aliphatic.

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