Synergistic disruptions in seuss cyp85A2 double mutants reveal a role for brassinolide synthesis during gynoecium and ovule development

<p>Abstract</p> <p>Background</p> <p>The Arabidopsis <it>SEUSS </it>(<it>SEU</it>) gene encodes a transcriptional adaptor protein that is required for a diverse set of developmental events, including floral organ identity specification, as well as gynoecium, ovule and embryo development. In order to better understand the molecular mechanisms of <it>SEUSS </it>action we undertook a genetic modifier screen to identify <it>seuss-modifier </it>(<it>sum</it>) mutations.</p> <p>Results</p> <p>Screening of M2 lines representing approximately 5,000 M1 individuals identified mutations that enhance the <it>seuss </it>mutant phenotypic disruptions in ovules and gynoecia; here we describe the phenotype of the <it>sum63 </it>mutant and enhanced disruptions of ovule and gynoecial development in the <it>seu sum63 </it>double mutant. Mapping and genetic complementation tests indicate that <it>sum63 </it>is allelic to <it>CYP85A2 </it>(AT3G30180) a cytochrome p450 enzyme that catalyzes the final steps in the synthesis of the phytohormone brassinolide.</p> <p>Conclusions</p> <p>Our identification of mutations in <it>CYP85A2 </it>as enhancers of the <it>seuss </it>mutant phenotype suggests a previously unrecognized role for brassinolide synthesis in gynoecial and ovule outer integument development. The work also suggests that <it>seuss </it>mutants may be more sensitive to the loss or reduction of brassinolide synthesis than are wild type plants.</p

Transcriptomic Characterization of a Synergistic Genetic Interaction during Carpel Margin Meristem Development in Arabidopsis thaliana

In flowering plants the gynoecium is the female reproductive structure. In Arabidopsis thaliana ovules initiate within the developing gynoecium from meristematic tissue located along the margins of the floral carpels. When fertilized the ovules will develop into seeds. SEUSS (SEU) and AINTEGUMENTA (ANT) encode transcriptional regulators that are critical for the proper formation of ovules from the carpel margin meristem (CMM). The synergistic loss of ovule initiation observed in the seu ant double mutant suggests that SEU and ANT share overlapping functions during CMM development. However the molecular mechanism underlying this synergistic interaction is unknown. Using the ATH1 transcriptomics platform we identified transcripts that were differentially expressed in seu ant double mutant relative to wild type and single mutant gynoecia. In particular we sought to identify transcripts whose expression was dependent on the coordinated activities of the SEU and ANT gene products. Our analysis identifies a diverse set of transcripts that display altered expression in the seu ant double mutant tissues. The analysis of overrepresented Gene Ontology classifications suggests a preponderance of transcriptional regulators including multiple members of the REPRODUCTIVE MERISTEMS (REM) and GROWTH-REGULATING FACTOR (GRF) families are mis-regulated in the seu ant gynoecia. Our in situ hybridization analyses indicate that many of these genes are preferentially expressed within the developing CMM. This study is the first step toward a detailed description of the transcriptional regulatory hierarchies that control the development of the CMM and ovule initiation. Understanding the regulatory hierarchy controlled by SEU and ANT will clarify the molecular mechanism of the functional redundancy of these two genes and illuminate the developmental and molecular events required for CMM development and ovule initiation

Models of classroom assessment for course-based research experiences

Course-based research pedagogy involves positioning students as contributors to authentic research projects as part of an engaging educational experience that promotes their learning and persistence in science. To develop a model for assessing and grading students engaged in this type of learning experience, the assessment aims and practices of a community of experienced course-based research instructors were collected and analyzed. This approach defines four aims of course-based research assessment—(1) Assessing Laboratory Work and Scientific Thinking; (2) Evaluating Mastery of Concepts, Quantitative Thinking and Skills; (3) Appraising Forms of Scientific Communication; and (4) Metacognition of Learning—along with a set of practices for each aim. These aims and practices of assessment were then integrated with previously developed models of course-based research instruction to reveal an assessment program in which instructors provide extensive feedback to support productive student engagement in research while grading those aspects of research that are necessary for the student to succeed. Assessment conducted in this way delicately balances the need to facilitate students’ ongoing research with the requirement of a final grade without undercutting the important aims of a CRE education

A Meta-study of Common Plant Biology Misconceptions Beyond Photosynthesis and Respiration

Educational research indicates that eradicating misconceptions may require that instructors explicitly address and correct them. Knowing what these misconceptions are is an important first step. Numerous misconceptions surrounding photosynthesis and respiration have been reported, but published articles focused on other aspects of plant biology are less abundant and scattered in the literature. In order to identify other misconceptions, we extensively screened the literature and found various student misconceptions about plant nutrition, classification, diffusion and osmosis, water relationships, ecology, reproduction, genetics, growth, development, plant and cellular structure, and defense. While misconceptions may vary in type and complexity in these areas, they permeate all age groups and levels of education, from preschool through pre-service educators. To assist educators in correcting these misconceptions through curriculum development, we have mapped these misconceptions onto the Core Concepts for Plant Biology Education as delineated by the American Society of Plant Biologists (ASPB) and the Botanical Society of America (BSA). Our mapping revealed a number of core concepts for which misconceptions have not been reported and warrant further research