High light and temperature reduce photosynthetic efficiency through different mechanisms in the C4 model Setaria viridis.

Funder: start-up funding from Donald Danforth Plant Science CenterC4 plants frequently experience high light and high temperature conditions in the field, which reduce growth and yield. However, the mechanisms underlying these stress responses in C4 plants have been under-explored, especially the coordination between mesophyll (M) and bundle sheath (BS) cells. We investigated how the C4 model plant Setaria viridis responded to a four-hour high light or high temperature treatment at photosynthetic, transcriptomic, and ultrastructural levels. Although we observed a comparable reduction of photosynthetic efficiency in high light or high temperature treated leaves, detailed analysis of multi-level responses revealed important differences in key pathways and M/BS specificity responding to high light and high temperature. We provide a systematic analysis of high light and high temperature responses in S. viridis, reveal different acclimation strategies to these two stresses in C4 plants, discover unique light/temperature responses in C4 plants in comparison to C3 plants, and identify potential targets to improve abiotic stress tolerance in C4 crops

Male Adolescents\u27 Knowledge of Sexual Partners

Knowledge of one\u27s sexual partners is a potential factor in one\u27s perceptions of vulnerability to sexually transmitted diseases (STDs). Adolescents may believe that they know more about their partners than they actually do. Having no information may be perceived as a person\u27s partner(s) not having risk factors for STDs. The current study investigated what a group of high-risk male adolescents actually knew about their partners and to what degree they were willing to admit that they did not know important risk information about their partners. The sample was 200 males between the ages of 13-17, primarily from a boys\u27 training school. The data for the study are from a larger study examining methods of collecting sensitive sexual information from adolescents and the factors that may influence their distortion of responses. The data to be presented are preliminary analyses of this larger data set. Participants were asked sexual behavior information and knowledge about sexual partners via one of three methods: (1) paper and pencil, (2) personal interview, or (3) computer interview. One set of questions deals with knowledge of sexual partners regarding information about sexual orientation, intravenous (IV) drug use, and whether they had or have an STD, including AIDS. One of the responses to these questions is I don\u27t know because I never asked. The results showed that this particular sample had a high level of risk behaviors. A significant portion of the sample admitted not knowing risk information about their partners. Specifically, three relationships were found between high-risk behavior and knowledge about partners

Comparative Phenotyping of Two Commonly Used Chlamydomonas reinhardtii Background Strains: CC-1690 (21gr) and CC-5325 (The CLiP Mutant Library Background)

The unicellular green alga Chlamydomonas reinhardtii is an excellent model organism to investigate many essential cellular processes in photosynthetic eukaryotes. Two commonly used background strains of Chlamydomonas are CC-1690 and CC-5325. CC-1690, also called 21gr, has been used for the Chlamydomonas genome project and several transcriptome analyses. CC-5325 is the background strain for the Chlamydomonas Library Project (CLiP). Photosynthetic performance in CC-5325 has not been evaluated in comparison with CC-1690. Additionally, CC-5325 is often considered to be cell-wall deficient, although detailed analysis is missing. The circadian rhythms in CC-5325 are also unclear. To fill these knowledge gaps and facilitate the use of the CLiP mutant library for various screens, we performed phenotypic comparisons between CC-1690 and CC-5325. Our results showed that CC-5325 grew faster heterotrophically in dark and equally well in mixotrophic liquid medium as compared to CC-1690. CC-5325 had lower photosynthetic efficiency and was more heat-sensitive than CC-1690. Furthermore, CC-5325 had an intact cell wall which had comparable integrity to that in CC-1690 but appeared to have reduced thickness. Additionally, CC-5325 could perform phototaxis, but could not maintain a sustained circadian rhythm of phototaxis as CC1690 did. Finally, in comparison to CC-1690, CC-5325 had longer cilia in the medium with acetate but slower swimming speed in the medium without nitrogen and acetate. Our results will be useful for researchers in the Chlamydomonas community to choose suitable background strains for mutant analysis and employ the CLiP mutant library for genome-wide mutant screens under appropriate conditions, especially in the areas of photosynthesis, thermotolerance, cell wall, and circadian rhythms