Heat shock-induced enhanced susceptibility of barley to Bipolaris sorokiniana is associated with elevated ROS production and plant defense-related gene expression

● Heat stress alters plant defense responses to pathogens. A short-term heat shock (HS) promotes infections by biotrophic pathogens. However, little is known about how HS affects infection by hemibiotrophic pathogens like Bipolaris sorokiniana (teleomorph: Cochliobolus sativus) (BS). We assessed the effect of HS in BS-susceptible barley (Hordeum vulgare cv. Ingrid) by monitoring leaf spot symptoms, BS biomass, reactive oxygen species (ROS) and plant defense-related gene expression following pre-exposure to HS. ● For HS, barley plants were kept at 49 °C for 20 seconds. BS biomass was assessed by qPCR, ROS levels determined by histochemical staining, while gene expression assayed by RT-qPCR. ● HS suppressed defense responses of barley to BS, resulting in more severe necrotic symptoms and increased fungal biomass, as compared to untreated plants. HS-induced increased susceptibility was accompanied by significant increases in ROS (superoxide, hydrogen peroxide). Transient expression of plant defense-related antioxidant genes and a barley programmed cell death inhibitor (HvBI-1) was induced in response to HS. However, HS followed by BS infection caused further transient increases in expression of HvSOD and HvBI-1 correlating with enhanced susceptibility. Expression of the HvPR-1b gene encoding pathogenesis-related (PR) protein-1b increased several fold at 24 hours after BS infection, however, HS further increased transcript levels along with enhanced susceptibility. ● HS induces enhanced susceptibility of barley to BS, associated with elevated ROS levels and expression of plant defense-related genes encoding antioxidants, a cell death inhibitor and PR-1b. Our results may contribute to elucidating the influence of HS on barley defense responses to hemibiotrophic pathogens.

Long non-coding RNA EGFR-AS1 in colorectal cancer: potential role in tumorigenesis and survival via miRNA-133b sponge and EGFR/STAT3 axis regulation

BACKGROUND

Colorectal cancer is one of the most common cancers worldwide and a major cause of cancer-related death. Thus molecular biomarkers for colorectal cancer have been proposed. The role of long non-coding RNA EGFR-AS1 in colorectal cancer is still unclear. We aimed to evaluate its expression in different stages of colorectal cancer and determine any possible role in regulating the miR‑133b/EGFR/STAT3 signalling pathway.

MATERIALS AND METHODS

The relative expression of EGFR-AS1 and miR‑133b were evaluated by quantitative real-time RT-transcription PCR in 130 colorectal cancer samples and 30 normal tissues. EGFR expression was assessed using immunohistochemistry. Furthermore, levels of p-EGFR, p-STAT3, and apoptotic proteins were determined by ELISA.

RESULTS

Both EGFR-AS1 and EGFR overexpression were positively linked with colorectal cancer status (both p < 0.01), grade (both p < 0.01), and metastasis (P < 0.01 and p = 0.019 respectively). EGFR-AS1 and miR-133b were significantly inversely correlated (P < 0.01). Low expression of miR-133b was inversely associated with overexpressed EGFR and increased p-STAT3 levels. EGFR-AS1 was an independent prognostic factor for survival of colorectal cancer patients (P < 0.01, HR 2.06; 95% CI 1.32-3.19) where low EGFR-AS1 expression was associated with higher survival rate (p = 0.003).

CONCLUSION

EGFR-AS1 may have a role in colorectal cancer by regulation of miR‑133b/EGFR/STAT3 signalling. It may be a potential biomarker for early diagnosis and predicting the survival rate of colorectal cancer.

Suppression of tobacco mosaic virus-induced hypersensitive-type necrotization in tobacco at high temperature is associated with downregulation of NADPH oxidase and superoxide and stimulation of dehydroascorbate reductase

Tissue necroses and resistance during the hypersensitive response (HR) of tobacco to tobacco mosaic virus (TMV) are overcome at temperatures above 28 degrees C and the virus multiplies to high levels in the originally resistant N-gene expressing plants. We have demonstrated that chemical compounds that generate reactive oxygen species (ROS) or directly applied hydrogen peroxide (H(2)O(2)) are able to induce HR-type necroses in TMV-inoculated Xanthi-nc tobacco even at high temperatures (e.g. 30 degrees C). The amount of superoxide (O(2)(*-)) decreased, while H(2)O(2) slightly increased in TMV- and mock-inoculated leaves at 30 degrees C, as compared with 20 degrees C. Activity of NADPH oxidase and mRNA levels of genes that encode NADPH oxidase and an alternative oxidase, respectively, were significantly lower, while activity of dehydroascorbate reductase was significantly higher at 30 degrees C, as compared with 20 degrees C. It was possible to reverse or suppress the chemically induced HR-type necrotization at 30 degrees C by the application of antioxidants, such as superoxide dismutase and catalase, demonstrating that the development of HR-type necroses indeed depends on a certain level of superoxide and other ROS. Importantly, high TMV levels at 30 degrees C were similar in infected plants, whether the HR-type necrotization developed or not. Suppression of virus multiplication in resistant, HR-producing tobacco at lower temperatures seems to be independent of the appearance of necroses but is associated with temperatures below 28 degrees C.