Transporter-Mediated Nuclear Entry of Jasmonoyl-lsoleucine Is Essential for Jasmonate Signaling

To control gene expression by directly responding to hormone concentrations, both animal and plant cells have exploited comparable mechanisms to sense small-molecule hormones in nucleus. Whether nuclear entry of these hormones is actively transported or passively diffused, as conventionally postulated, through the nuclear pore complex, remains enigmatic. Here, we identified and characterized a jasmonate transporter in Arabidopsis thaliana, AtJAT1/AtABCG16, which exhibits an unexpected dual localization at the nuclear envelope and plasma membrane. We show that AtJAT1/AtABCG16 controls the cytoplasmic and nuclear partition of jasmonate phytohormones by mediating both cellular efflux of jasmonic acid （JA） and nuclear influx of jasmonoyl-isoleucine （JA-Ile）, and is essential for maintaining a critical nuclear JA-Ile concentration to activate JA signaling. These results illustrate that transporter-mediated nuclear entry of small hormone molecules is a new mechanism to regulate nuclear hormone signaling. Our findings provide an avenue to develop pharmaceutical agents targeting the nuclear entry of small molecules.

Simple and rapid determination of dioxin in fish and sea food using a highly sensitive reporter cell line,CBG 2.8D

Food,especially animal origin food is the main source of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs),and dioxin-like polychlorinated biphenyls(dl-PCBs)for human exposure.So,a simple,rapid and cheap bioassay method is needed for determination of dioxins in food samples.In this study,we used a new highly sensitive reporter cell line to determine the concentration of dioxins in 33 fish and seafood samples.The samples were extracted by shaking with water/isopropanol(1:1 v/v)and hexane and cleaned-up by a multi layered silica gel column and an alumina column,then analyzed using CBG 2.8 D cell line.We compared the results obtained from the CBG 2.8 D cell assay to those obtained from conventional High-Resolution Gas Chromatography-High Resolution Mass Spectrometry(HRGC-HRMS)analysis.Good correlations were observed between these two methods(r^2=0.93).While the slope of regression line was 1.76,the bioanalytical equivalent(BEQ)values were 1.76 folds higher than WHO-TEQ values and the conversion coefficient was 0.568(the reciprocal of 1.76).In conclusion,CBG 2.8 D cell assay was an applicable method to determine dioxins levels in fish and sea food samples.