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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.

BackgroundThe Arabidopsis SEUSS (SEU) 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 SEUSS action we undertook a genetic modifier screen to identify seuss-modifier (sum) mutations.ResultsScreening of M2 lines representing approximately 5,000 M1 individuals identified mutations that enhance the seuss mutant phenotypic disruptions in ovules and gynoecia; here we describe the phenotype of the sum63 mutant and enhanced disruptions of ovule and gynoecial development in the seu sum63 double mutant. Mapping and genetic complementation tests indicate that sum63 is allelic to CYP85A2 (AT3G30180) a cytochrome p450 enzyme that catalyzes the final steps in the synthesis of the phytohormone brassinolide.ConclusionsOur identification of mutations in CYP85A2 as enhancers of the seuss mutant phenotype suggests a previously unrecognized role for brassinolide synthesis in gynoecial and ovule outer integument development. The work also suggests that seuss mutants may be more sensitive to the loss or reduction of brassinolide synthesis than are wild type plants.

No abstract

Plants are ubiquitous and found in virtually every ecosystem on Earth, but their biology is often poorly understood, and inaccurate ideas about how plants grow and function abound. Many articles have been published documenting student misconceptions about photosynthesis and respiration, but there are substantially fewer on such topics as plant cell structure and growth; plant genetics, evolution, and classification; plant physiology (beyond energy relations); and plant ecology. The available studies of misconceptions held on those topics show that many are formed at a very young age and persist throughout all educational levels. Our goal is to begin building a central resource of plant biology misconceptions that addresses these underrepresented topics, and here we provide a table of published misconceptions organized by topic. For greater utility, we report the age group(s) in which the misconceptions were found and then map them to the ASPB – BSA Core Concepts and Learning Objectives in Plant Biology for Undergraduates, developed jointly by the American Society of Plant Biologists and the Botanical Society of America.