Showing papers by "Bonnie Bartel published in 2011"
TL;DR: The accumulating evidence suggesting that the IAA precursor indole-3-butyric acid (IBA) is transported independently of the characterized IAA transport machinery along with the recent identification of specific IBA efflux carriers and enzymes suggested to metabolize IBA are discussed.
175 citations
TL;DR: The decreased auxin levels and responsiveness are uncovered, along with the associated developmental defects, and previously unappreciated roles for IBA-derived IAA during seedling development are established, establishing IBA as an important auxin precursor, and it is suggested that I BA-to-IAA conversion contributes to the positive feedback that maintains root auxin Levels.
Abstract: Levels of auxin, which regulates both cell division and cell elongation in plant development, are controlled by synthesis, inactivation, transport, and the use of storage forms. However, the specific contributions of various inputs to the active auxin pool are not well understood. One auxin precursor is indole-3-butyric acid (IBA), which undergoes peroxisomal β-oxidation to release free indole-3-acetic acid (IAA). We identified ENOYL-COA HYDRATASE2 (ECH2) as an enzyme required for IBA response. Combining the ech2 mutant with previously identified iba response mutants resulted in enhanced IBA resistance, diverse auxin-related developmental defects, decreased auxin-responsive reporter activity in both untreated and auxin-treated seedlings, and decreased free IAA levels. The decreased auxin levels and responsiveness, along with the associated developmental defects, uncover previously unappreciated roles for IBA-derived IAA during seedling development, establish IBA as an important auxin precursor, and suggest that IBA-to-IAA conversion contributes to the positive feedback that maintains root auxin levels.
136 citations
TL;DR: It is found that PEX14 facilitates, but is not essential for peroxisomal matrix protein import in plants, as pex14 plants matured, import improved.
Abstract: Mutations in peroxisome biogenesis proteins (peroxins) can lead to developmental deficiencies in various eukaryotes. PEX14 and PEX13 are peroxins involved in docking cargo-receptor complexes at the peroxisomal membrane, thus aiding in the transport of the cargo into the peroxisomal matrix. Genetic screens have revealed numerous Arabidopsis thaliana peroxins acting in peroxisomal matrix protein import; the viable alleles isolated through these screens are generally partial loss-of-function alleles, whereas null mutations that disrupt delivery of matrix proteins to peroxisomes can confer embryonic lethality. In this study, we used forward and reverse genetics in Arabidopsis to isolate four pex14 alleles. We found that all four alleles conferred reduced PEX14 mRNA levels and displayed physiological and molecular defects suggesting reduced but not abolished peroxisomal matrix protein import. The least severe pex14 allele, pex14-3, accumulated low levels of a C-terminally truncated PEX14 product that retained partial function. Surprisingly, even the severe pex14-2 allele, which lacked detectable PEX14 mRNA and PEX14 protein, was viable, fertile, and displayed residual peroxisome matrix protein import. As pex14 plants matured, import improved. Together, our data indicate that PEX14 facilitates, but is not essential for peroxisomal matrix protein import in plants.
39 citations
TL;DR: Examination of genetic interactions among Arabidopsis peroxin mutants found that the weak pex13‐1 allele had deleterious effects when combined with pex5‐1 and pex14‐2, which are defective in early‐acting peroxins, as shown by reduced matrix protein import and enhanced physiological defects.
Abstract: Proteins are targeted to the peroxisome matrix via processes that are mechanistically distinct from those used by other organelles. Protein entry into peroxisomes requires peroxin (PEX) proteins, including early-acting receptor (e.g. PEX5) and docking peroxins (e.g. PEX13 and PEX14) and late-acting PEX5-recycling peroxins (e.g. PEX4 and PEX6). We examined genetic interactions among Arabidopsis peroxin mutants and found that the weak pex13-1 allele had deleterious effects when combined with pex5-1 and pex14-2, which are defective in early-acting peroxins, as shown by reduced matrix protein import and enhanced physiological defects. In contrast, combining pex13-1 with pex4-1 or pex6-1, which are defective in late-acting peroxins, unexpectedly ameliorated mutant growth defects. Matrix protein import remained impaired in pex4-1 pex13-1 and pex6-1 pex13-1, suggesting that the partial suppression of pex4-1 and pex6-1 physiological defects by a weak pex13 allele may result from restoring the balance between import and export of PEX5 or other proteins that are retrotranslocated from the peroxisome with the assistance of PEX4 and PEX6. Our results suggest that symptoms caused by pex mutants defective in late-acting peroxins may result not only from defects in matrix protein import but also from inefficient removal of PEX5 from the peroxisomal membrane following cargo delivery.
35 citations
Howard University1, University of Wisconsin-Madison2, University of California, Santa Cruz3, University of California, Los Angeles4, Rice University5, Emory University6, Massachusetts Institute of Technology7, Washington University in St. Louis8, Brandeis University9, Vanderbilt University10, Medical University of South Carolina11, Yale University12, University of Pittsburgh13, Cornell University14, Columbia University15, University of Colorado Boulder16, Harvard University17, University of Illinois at Urbana–Champaign18, University of Minnesota19, University of California, Irvine20, University of Utah21, University of California, San Diego22, University of California, Berkeley23, Tufts University24, Louisiana State University25, University of California, Riverside26, Duke University27, Stanford University28
TL;DR: An Editorial Expression of Concern approaches to science teaching, curricular design, and mentoring and strongly endorse the recommendation for transition to a competency-based curriculum for pre- medical education.
Abstract: COMMENTARY Gallery of ocean life Attributing weather for policy? LETTERS I BOOKS I POLICY FORUM I EDUCATION FORUM I PERSPECTIVES LETTERS edited by Jennifer Sills THE REPORT “COPING WITH CHAOS: HOW DISORDERED CONTEXTS PROMOTE STEREOTYPING AND discrimination” by D. A. Stapel and S. Lindenberg (1) reported the effects of the physi- cal environment on human stereotyping and discriminatory behavior. On 31 October 2011, Tilburg University held a press conference to announce interim fi ndings of its investiga- tion into possible data fraud in the body of work published by Stapel. The offi cial report in Dutch (translated into English using Google software) indicates that the extent of the fraud by Stapel is substantial. Pending further details of the Tilburg Committee’s fi ndings, Science is publishing this Editorial Expression of Concern to alert our readers that serious concerns have been raised about the validity of the fi ndings in this Report. BRUCE ALBERTS Editor-in-Chief Reference 1. D. A. Stapel, S. Lindenberg, Science 332, 251 (2011). Published online 1 November 2011; 10.1126/science.1216027 IN 2009, THE ASSOCIATION OF AMERICAN Medical Colleges (AAMC), in collaboration with the Howard Hughes Medical Institute (HHMI), reviewed the educational prereq- uisites for admission to medical school in the United States. Because a large fraction of undergraduate students enroll in science courses to meet the requirements for admis- sion to medical school, courses satisfy- ing these requirements dominate the under- graduate science curriculum. The prescribed course structure has impeded educational innovation, particularly the development of new, multidisciplinary courses. To address this situation, the AAMC- HHMI report (1) recommends that scien- tifi c competencies replace specifi c courses as requirements for medical school admis- sions. They recommend that students “dem- onstrate both knowledge of and ability to use basic principles of mathematics and statis- tics, physics, chemistry, biochemistry, and biology needed for the application of the sci- ences to human health and disease; demon- strate observational and analytical skills and the ability to apply those skills and principles to biological situations.” The report articu- lates eight competencies in the areas of scien- tifi c knowledge and reasoning and provides learning objectives with examples in each of these areas, independent of the identity of the specifi c courses taken to achieve these com- petencies. In March 2011, a committee of the AAMC released preliminary recommenda- tions (2) for changes to the Medical College Admission Test based on this report, with planned implementation in 2015. We are HHMI professors who share the goal of promoting excellence in science edu- cation through the development of novel 11 NOVEMBER 2011 WINSTON A. ANDERSON, 1 RICHARD M. AMASINO, 2 MANUEL ARES JR., 3 UTPAL BANERJEE, 4 BONNIE BARTEL, 5 VICTOR G. CORCES, 6 CATHERINE L. DRENNAN, 7 SARAH C. R. ELGIN, 8 IRVING R. EPSTEIN, 9 ELLEN FANNING, 10 LOUIS J. CREDIT: ISTOCKPHOTOS Competencies: A Cure for Pre-Med Curriculum Downloaded from www.sciencemag.org on August 8, 2014 Editorial Expression of Concern approaches to science teaching, curricular design, and mentoring. We strongly endorse the recommendation for transition to a competency-based curriculum for pre- medical education. There is room for dis- cussion about which specifi c competencies should be included, and there is a need to ensure that curricular changes do not dilute course content, but we foresee that this inno- vation will have a substantial positive impact toward the invigoration of undergraduate education in science, math, and engineer- ing. Specifi cally, it will simplify the develop- ment and implementation of course offerings within and between traditional disciplines as well as facilitate greater curricular innovation by science departments and multidisciplinary programs. Adoption of these reforms will provide enhanced opportunities to introduce curricular innovations that match the partic- ular strengths of individual institutions and stimulate a widespread discussion of creative advancements in undergraduate education. N ow is the time for science faculty to convene to reconsider what all future scien- tists (not just medical doctors) should know and how that material should be taught in their institutions. We encourage discussions within and between science departments of curricular revisions that take advantage of this enhanced fl exibility in keeping with the competencies recommended by the HHMI- AAMC report. VOL 334 SCIENCE www.sciencemag.org Published by AAAS
2 citations