A Technique for Measuring Petal Gloss, with Examples from the Namaqualand Flora

The degree of floral gloss varies between species. However, little is known about this distinctive floral trait, even though it could be a key feature of floral biotic and abiotic interactions. One reason for the absence of knowledge is the lack of a simple, repeatable method of gloss measurement that can be used in the field to study floral gloss. A protocol is described for measuring gloss in petal samples collected in the field, using a glossmeter. Repeatability of the technique is assessed. We demonstrate a simple yet highly accurate and repeatable method that can easily be implemented in the field. We also highlight the huge variety of glossiness found within flowers and between species in a sample of spring-blooming flowers collected in Namaqualand, South Africa. We discuss the potential uses of this method and its applications for furthering studies in plant-pollinator interactions. We also discuss the potential functions of gloss in flowers

Parallels between Pathogens and Gluten Peptides in Celiac Sprue

Pathogens are exogenous agents capable of causing disease in susceptible organisms. In celiac sprue, a disease triggered by partially hydrolyzed gluten peptides in the small intestine, the offending immunotoxins cannot replicate, but otherwise have many hallmarks of classical pathogens. First, dietary gluten and its peptide metabolites are ubiquitous components of the modern diet, yet only a small, genetically susceptible fraction of the human population contracts celiac sprue. Second, immunotoxic gluten peptides have certain unusual structural features that allow them to survive the harsh proteolytic conditions of the gastrointestinal tract and thereby interact extensively with the mucosal lining of the small intestine. Third, they invade across epithelial barriers intact to access the underlying gut-associated lymphoid tissue. Fourth, they possess recognition sequences for selective modification by an endogenous enzyme, transglutaminase 2, allowing for in situ activation to a more immunotoxic form via host subversion. Fifth, they precipitate a T cell–mediated immune reaction comprising both innate and adaptive responses that causes chronic inflammation of the small intestine. Sixth, complete elimination of immunotoxic gluten peptides from the celiac diet results in remission, whereas reintroduction of gluten in the diet causes relapse. Therefore, in analogy with antibiotics, orally administered proteases that reduce the host's exposure to the immunotoxin by accelerating gluten peptide destruction have considerable therapeutic potential. Last but not least, notwithstanding the power of in vitro methods to reconstitute the essence of the immune response to gluten in a celiac patient, animal models for the disease, while elusive, are likely to yield fundamentally new systems-level insights

Light sheet microscopy imaging of light absorption and photosynthesis distribution in plant tissue

© 2017 American Society of Plant Biologists. All Rights Reserved. In vivo variable chlorophyll fluorescence measurements of photosystem II (PSII) quantum yields in optically dense systems are complicated by steep tissue light gradients due to scattering and absorption. Consequently, externally measured effective PSII quantum yields may be composed of signals derived from cells differentially exposed to actinic light, where cells located deeper inside tissues receive lower irradiance than cells closer to the surface and can display distinct photophysiological status. We demonstrate how measured distributions of PSII quantum yields in plant tissue change under natural tissue light gradients as compared with conventionally measured quantum yields with even exposure to actinic light. This was achieved by applying actinic irradiance perpendicular to one side of thallus cross sections of the aquatic macrophyte Fucus vesiculosus with laser light sheets of defined spectral composition, while imaging variable chlorophyll fluorescence from cross sections with a microscope-mounted pulse amplitudemodulated imaging system. We show that quantum yields are highly affected by light gradients and that traditional surface-based variable chlorophyll fluorescence measurements result in substantial underestimations and/or overestimations, depending on incident actinic irradiance. We present a method for using chlorophyll fluorescence profiles in combination with integrating sphere measurements of reflectance and transmittance to calculate depth-resolved photon absorption profiles, which can be used to correct apparent PSII electron transport rates to photons absorbed by PSII. Absorption profiles of the investigated aquatic macrophyte were different in shape from what is typically observed in terrestrial leaves, and based on this finding,we discuss strategies for optimizing photon absorption via modulation of the structural organization of phytoelements according to in situ light environments