Members of the Joint Working Group on Improving Underrepresented Minorities (URMs) Persistence in Science, Technology, Engineering and Mathematics (STEM), utilizing Kurt Lewin’s planned approach to change, describe five recommendations to increase URM persistence in STEM at the undergraduate level.

Differential sensitivity to the oxidant paraquat was observed in pea (Pisum sativum L.) based on cultivar and leaf age. To assess contributions of inductive responses of the antioxidant enzymes in short-term resistance to oxidative damage, activities of glutathione reductase (CR), superoxide dismutase (SOD), and ascorbate peroxidase (APX) and transcript levels for plastidic CR, Cu,Zn SOD, and cytosolic APX were determined. Responses to paraquat exposure from three different leaf age classes of pea were studied. Resistance was correlated with leaf age, photosynthetic rates, enzyme activities, and pretreatment levels of plastid CR and plastid Cu,Zn SOD transcripts. In response to paraquat, small increases in activities of CR and APX were observed in the more resistant leaves. These changes were not reflected at the mRNA leve1 for the plastidic CR or Cu,Zn SOD. Paraquat-mediated increases in cytosolic APX mRNA occurred in all leaf types, irrespective of resistance. Developmentally controlled mechanisms determining basal antioxidant enzyme activities, and not inductive responses, appear to be critical factors mediating short-term oxidative stress resistance.

Previously we reported the presence of a soluble phosphatidylinositol 4-kinase (PI 4-kinase) in carrot (Daucus carofa L.) suspension culture cells (C.M. Okpodu, W. Cross, W.F. Boss 119901 Plant Physiol 93: S-63). We have purified the enzyme over 1000-fold using Q-Sepharose ion exchange, hydroxylapatite, and G-1 O0 gel filtration column chromatography. The M, of the enzyme was estimated to be 83,000 by gel filtration. PI 4-kinase activity was recovered after renaturation of the 80-kD region of polyacrylamide gels, and an 80-kD peptide cross-reacted with antibodies to the yeast 55-kD membrane-associated PI 4-kinase on western blots. l h e isolated lipid kinase phosphorylated PI but not lysophosphatidylinosito1 or phosphatidylinositol monophosphate. Maximal PI kinase activity occurred when the substrate was added as Triton X-lOO/PI mixed micelles at pH 8. The enzyme required divalent cations. At low concentrations (1-5 mM), Mn2+ was more effective than Mgz+ in increasing enzyme activity; however, maximal activity occurred at 25 to 40 mM Mgz+. Calcium from 0.01 p~ to 1 mM had no effect on the enzyme activity. The K,,, of the enzyme for ATP was estimated to be between 400 and 463 p~. The enzyme was inhibited by adenosine (100 p~) ; however, ADP (up to 100 p~) had no effect on the activity. The biochemical characteristics of the carrot soluble PI 4-kinase are compared with the previously reported PI 4-kinases from animals and yeast.

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