Rapeseed is a very important oil crop in China; however, its production is challenging due to the absence of effective weed management strategies.  This is predominantly because of a shortage of herbicide resistance genes.  Acetohydroxyacid synthase (AHAS) herbicides inhibit AHAS, a key enzyme involved in branched-chain amino acid synthesis that is required for plant growth.  A rapeseed line designated M342 with AHAS herbicide resistance was developed through seed mutagenesis and was studied to assess the level and mode of inheritance of the resistance and to identify the molecular basis of resistance.  M342 possessed a high level of cross-resistance to sulfonylureas (SUs) and imidazolinones (IMIs).  This resistance was due to AHAS insensitivity to these herbicides and was inherited as a dominant trait conferred by a single nuclear-encoded gene.  Molecular analysis revealed the presence of a Trp574Leu mutation in M342, and an allele-specific cleaved amplified polymorphic sequence (AS-CAPS) marker was developed and cosegregated with herbicide resistance in the F₂, BC₁, and BC₂ populations.  This mutation altered the transcript levels of BnAHAS1 and BnAHAS3 in M342 compared with those in the wild type, but it did not affect the agronomic or quality traits.  The simple genetic inheritance of this mutation and the availability of the cleaved amplified polymorphic sequence (CAPS) marker and herbicide resistance gene should facilitate the development of herbicide-resistant rapeseed cultivars for effective weed control in China.  

Bacillus thuringiensis subspecies morrisoni strain HD12, whose genome harbors multiple insecticidal protein-encoding genes, includes eight cry genes, as indicated by genome sequencing.  This strain produces crystals that are toxic to lepidopteran species.  These crystal inclusions were purified by sucrose gradients and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), followed by liquid chromatography-mass spectrometry, and found to contain five proteins (Cry1Da, Cry1Ae, Cry1Bb, Cry1Fb, and Cry1Ja).  The transcriptional activities of the cry1Da, cry1Ae, cry1Bb, cry1Fb, and cry1Ja promoters indicated that transcription of cry1Da is controlled by SigE; however, the other four cry genes were found to be controlled by both SigE and SigK.  The activities of the cry1Ja and cry1Fb promoters were the strongest among the five genes studied.  These promoters were therefore used to direct the expression of the Cry1Ac- and Cry2Ab-encoding genes concurrently in a single strain.  Our findings indicate that promoters with the same transcriptional profile may be used to direct the expression of different cry genes in one strain.  Our results are expected to be valuable for the construction of strains with efficient expression of multiple cry genes in order to overcome current limitations associated with the application of B. thuringiensis-based insecticides.

Water and nitrogen are primary limiting factors in semiarid grassland ecosystems. Our knowledge is still poor regarding the interactive effects of water and N addition on soil microbial communities, although this information is crucial to reveal the mechanisms of the terrestrial ecosystem response to global changes. We addressed this problem by conducting a field experiment with a 15% surplus of the average rainfall under three levels of N addition (50, 100, and 200 kg N ha–1 yr–1) in two consecutive years in Inner Mongolia, China. Microbial community composition and functional diversity were analyzed based on phospholipid fatty acids (PLFA) and BIOLOG techniques, respectively. The results showed that water addition did not affect the soil microbial community composition, but much more yearly precipitation generally decreased the PLFA concentration, which implied a fast response of soil microbes to changes of water condition. Soil fungi was depressed only by N addition at the high level (200 kg N ha–1 yr–1) and without hydrologic leaching, while Gram-negative bacteria was suppressed probably by plant competition at high level N addition but with hydrologic leaching. The study found unilateral positive/negative interactions between water and N addition in affecting soil microbial community, however, climate condition (precipitation) could be a significant factor in disturbing the interactions. This study highlighted that: (1) The sustained effect of pulsed water addition was minimal on the soil microbial community composition but significant on the microbial community functional diversity and (2) the complex interaction between water and N addition on soil microbial community related to the inter-annual variation of the climate and plant response.