Arabidopsis thaliana histidine phosphotransfer proteins (AHPs) are similar to bacterial and yeast histidine phosphotransfer proteins (HPts), which act in multistep phosphorelay signaling pathways. A phosphorelay pathway is the current model for cytokinin signaling. To assess the role of AHPs in cytokinin signaling, we isolated T-DNA insertions in the five AHP genes that are predicted to encode functional HPts and constructed multiple insertion mutants, including an ahp1,2,3,4,5 quintuple mutant. Single ahp mutants were indistinguishable from wild-type seedlings in cytokinin response assays. However, various higher-order mutants displayed reduced sensitivity to cytokinin in diverse cytokinin assays, indicating both a positive role for AHPs in cytokinin signaling and functional overlap among the AHPs. In contrast with the other four AHPs, AHP4 may play a negative role in some cytokinin responses. The quintuple ahp mutant showed various abnormalities in growth and development, including reduced fertility, increased seed size, reduced vascular development, and a shortened primary root. These data indicate that most of the AHPs are redundant, positive regulators of cytokinin signaling and affect multiple aspects of plant development.

Despite the proliferation of loyalty programs in a wide range of categories, there is little empirical research that focuses on the measurement of such programs. The key to measuring the influence of loyalty programs is that they operate as dynamic incentive schemes by providing benefits based on cumulative purchasing over time. As such, loyalty programs encourage consumers to shift from myopic or single-period decision making to dynamic or multiple-period decision making. In this study, the author models customers' response to a loyalty program under the assumption that purchases represent the sequential choices of customers who are solving a dynamic optimization problem. The author estimates the theoretical model using a discrete-choice dynamic programming formulation. The author evaluates a specific loyalty program with data from an online merchant that specializes in grocery and drugstore items. Through simulation and policy experiments, it is possible to evaluate and compare the long-term effects of the loyalty program and other marketing instruments (e.g., e-mail coupons, fulfillment rates, shipping fees) on customer retention. Empirical results and policy experiments suggest that the loyalty program under study is successful in increasing annual purchasing for a substantial proportion of customers.

Background There has been an increase in non-daily smoking, alternative tobacco product and marijuana use among young adults in recent years. Objectives This study examined perceptions of health risks, addictiveness, and social acceptability of cigarettes, cigar products, smokeless tobacco, hookah, electronic cigarettes, and marijuana among young adults and correlates of such perceptions. Methods In Spring 2013, 10,000 students at two universities in the Southeastern United States were recruited to complete an online survey (2,002 respondents), assessing personal, parental, and peer use of each product; and perceptions of health risks, addictiveness, and social acceptability of each of these products. Results Marijuana was the most commonly used product in the past month (19.2%), with hookah being the second most commonly used (16.4%). The least commonly used were smokeless tobacco products (2.6%) and electronic cigarettes (4.5%). There were high rates of concurrent product use, particularly among electronic cigarette users. The most positively perceived was marijuana, with hookah and electronic cigarettes being second. While tobacco use and related social factors, related positively, influenced perceptions of marijuana, marijuana use and related social factors were not associated with perceptions of any tobacco product. Conclusions/Importance Marketing efforts to promote electronic cigarettes and hookah to be safe and socially acceptable seem to be effective, while policy changes seem to be altering perceptions of marijuana and related social norms. Research is needed to document the health risks and addictive nature of emerging tobacco products and marijuana and evaluate efforts to communicate such risks to youth.

Cys2/His2-type zinc finger proteins, which contain the EAR transcriptional repressor domain, are thought to play a key role in regulating the defense response of plants to biotic and abiotic stress conditions. Although constitutive expression of several of these proteins was shown to enhance the tolerance of transgenic plants to abiotic stress, it is not clear whether the EAR-motif of these proteins is involved in this function. In addition, it is not clear whether suppression of plant growth, induced in transgenic plants by different Cys2/His2 EAR-containing proteins, is mediated by the EAR-domain. Here we report that transgenic Arabidopsis plants constitutively expressing the Cys2/His2 zinc finger protein Zat7 have suppressed growth and are more tolerant to salinity stress. A deletion or a mutation of the EAR-motif of Zat7 abolishes salinity tolerance without affecting growth suppression. These results demonstrate that the EAR-motif of Zat7 is directly involved in enhancing the tolerance of transgenic plants to salinity stress. In contrast, the EAR-motif appears not to be involved in suppressing the growth of transgenic plants. Further analysis of Zat7 using RNAi lines suggests that Zat7 functions in Arabidopsis to suppress a repressor of defense responses. A yeast two-hybrid analysis identified putative interactors of Zat7 and the EAR-domain, including WRKY70 and HASTY, a protein involved in miRNA transport. Our findings demonstrate that the EAR-domain of Cys2/His2-type zinc finger proteins plays a key role in the defense response of Arabidopsis to abiotic stresses.

Genetic control of branching is a primary determinant of yield, regulating seed number and harvesting ability, yet little is known about the molecular networks that shape grain-bearing inflorescences of cereal crops. Here, we used the maize (Zea mays) inflorescence to investigate gene networks that modulate determinacy, specifically the decision to allow branch growth. We characterized developmental transitions by associating spatiotemporal expression profiles with morphological changes resulting from genetic perturbations that disrupt steps in a pathway controlling branching. Developmental dynamics of genes targeted in vivo by the transcription factor RAMOSA1, a key regulator of determinacy, revealed potential mechanisms for repressing branches in distinct stem cell populations, including interactions with KNOTTED1, a master regulator of stem cell maintenance. Our results uncover discrete developmental modules that function in determining grass-specific morphology and provide a basis for targeted crop improvement and translation to other cereal crops with comparable inflorescence architectures.