Stripe Rust Effector Pst_9302 Inhibits Wheat Immunity to Promote Susceptibility.

Puccinia striiformis f. sp. tritici is an obligate biotrophic fungus that causes destructive stripe rust disease in wheat. During infection, Pst secretes virulence effectors via a specific infection structure-the haustorium-inside host cells to disturb host immunity and promote fungal colonization and expansion. Hence, the identification and functional analyses of Pst effectors are of great significance in deciphering the Pst pathogenicity mechanism. Here, we identified one candidate Pst effector Pst_9302 that could suppress Bax-triggered cell death in Nicotiana benthamiana. qRT-PCR analyses showed that the transcript levels of Pst_9302 were highly increased during the early infection stages of Pst. The transient expression of Pst_9302 in wheat via the type-three secretion system (T3SS) significantly inhibited the callose deposition induced by Pseudomonas syringae EtHAn. During wheat-Pst interaction, Pst_9302 overexpression suppressed reactive oxygen species (ROS) accumulation and cell death caused by the avirulent Pst race CYR23. The host-induced gene silencing (HIGS) of Pst_9302 resulted in decreased Pst pathogenicity with reduced infection area. The results suggest that Pst_9302 plays a virulence role in suppressing plant immunity and promoting Pst pathogenicity. Moreover, wheat voltage-dependent anion channel 1 protein (TaVDAC1) was identified as candidate Pst_9302-interacting proteins by yeast two-hybrid (Y2H) screening. Pull-down assays using the His-Pst_9302 and GST-TaVDAC1 protein verified their interactions. These results suggest that Pst_9302 may modulate wheat TaVDAC1 to regulate plant immunity.

Research progress on supercritical CO2 thickeners.

According to the thickening principle and molecular structure of thickeners, supercritical carbon dioxide (scCO2) thickeners have been summarized and introduced by dividing into polymers, small molecular compounds and surfactants. The properties such as solubility, thickening effect, thickening condition and existing problems of scCO2 thickeners are analyzed and assessed, and the research progress and prospects of scCO2 thickeners are proposed. ScCO2 is used in both CO2 fracturing and CO2 flooding for enhanced oil recovery (EOR). However, due to its low viscosity, the proppant carrying ability and filtration control ability of scCO2 are too weak for fracturing. Also, in the process of CO2 flooding, its low viscosity not only exacerbates the gravity override but also leads to an unfavorable mobility ratio that results in viscous fingering, early breakthrough, and poor sweep efficiency. Therefore, scCO2 thickeners have good application prospects in oil and gas production for improved oil recovery (IOR).