Very primitive hematopoietic stem cells have been identified as side population cells based on their ability to efflux a fluorescent vital dye, Hoechst 33342. In this study we show that keratinocytes with the same side population phenotype are also present in the human epidermis. Although side population keratinocytes have the same dye-effluxing phenotype as bone marrow side population cells and can be blocked by verapamil, they do not express increased levels of the ABCG2 transporter that is believed to be responsible for the bone marrow side population phenotype. Because bone marrow side population cells have stem cell characteristics, we sought to determine if side population keratinocytes represent a keratinocyte stem cell population by comparing side population keratinocytes with a traditional keratinocyte stem cell candidate, label-retaining keratinocytes. Flow cytometric analyses demonstrated that side population keratinocytes have a different cell surface phenotype (low beta1 integrin and low alpha6 integrin expression) than label-retaining keratinocytes and represent a unique population of keratinocytes distinctly different from the traditional keratinocyte stem cell candidate. Future in vivo studies will be required to analyze the function of side population keratinocytes in epidermal homeostasis and to determine if side population keratinocytes have characteristics of keratinocyte stem cells.

Weather-damaged wheat from northern New South Wales in 1995-96 was heavily infected with the fungus Alternaria alternata. The mycotoxins tenuazonic acid, alternariol, and alternariol monomethyl ether were detected at low levels which corresponded with the degree of A. alternata infection and the geographical location. Sorghum and undamaged wheat from the same region also showed moderate levels of A. alternata infection and low levels of tenuazonic acid but none of the other toxins. These mycotoxins were not found in weather-damaged wheat from other areas of Australia where the primary infection was by A. infectoria rather than A. alternata.

Jackson, K. L., Yin, J., and Ji, P. 2012. Sensitivity of Phytophthora capsici on vegetable crops in Georgia to mandipropamid, dimethomorph, and cyazofamid. Plant Dis. 96:1337-1342. Phytophthora blight, caused by Phytophthora capsici, is a seriotis disease in vegetable production, and selective use of fungicides continues to be a significant component of disease management programs. The effect of three chemical compounds-mandipropamid, dimethomorph, and cyazofamid-on asexual stages of P. capsici collected from bell pepper and cucurbits in Georgia was assessed in this study. Forty isolates of P. capsici were determined to be sensitive to mandipropamid and dimethomorph based on mycelial growth, zoospore germination, and sporangial production. Concentrations that were 50% effsctive (EC50 values) of mandipropamid that inhibited mycelial growth, zoospore germination, and sporangial production of the isolates averaged 0.03, 5.70, and 0.02 (ig/ml, respectively. EC50 values of dimethomorph in inhibiting mycelial growth, zoospore germination, and sporangial production averaged 0.24, 0.10, and 0.46 Mg/ml, respectively. The majority of isolates were either resistant or intermediateiy sensitive to cyazofamid at 500 pg/ml or lower concentrations based on mycelial growth or sporangial production, although all the isolates were sensitive to this compound based on zoospore germination, with an average EC50 of 0.04 |jg/ml. The results indicated that P. capsici populations in Georgia have not developed resistance to mandipropamid and cimethomorph whereas, for the majority of the isolates, certain asexual stages were resistant to cyazofamid.

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