A high-resolution method for the localization of proanthocyanidins in plant tissues

Background

Histochemical staining of plant tissues with 4-dimethylaminocinnamaldehyde (DMACA) or vanillin-HCl is widely used to characterize spatial patterns of proanthocyanidin accumulation in plant tissues. These methods are limited in their ability to allow high-resolution imaging of proanthocyanidin deposits.

Results

Tissue embedding techniques were used in combination with DMACA staining to analyze the accumulation of proanthocyanidins in Lotus corniculatus (L.) and Trifolium repens (L.) tissues. Embedding of plant tissues in LR White or paraffin matrices, with or without DMACA staining, preserved the physical integrity of the plant tissues, allowing high-resolution imaging that facilitated cell-specific localization of proanthocyanidins. A brown coloration was seen in proanthocyanidin-producing cells when plant tissues were embedded without DMACA staining and this was likely to have been due to non-enzymatic oxidation of proanthocyanidins and the formation of colored semiquinones and quinones.

Conclusions

This paper presents a simple, high-resolution method for analysis of proanthocyanidin accumulation in organs, tissues and cells of two plant species with different patterns of proanthocyanidin accumulation, namely Lotus corniculatus (birdsfoot trefoil) and Trifolium repens (white clover). This technique was used to characterize cell type-specific patterns of proanthocyanidin accumulation in white clover flowers at different stages of development.     

Photoreceptor regulation of CONSTANS protein in photoperiodic flowering

Many plants flower in response to seasonal fluctuations in day length. The CONSTANS (CO) gene of Arabidopsis promotes flowering in long days. Flowering is induced when CO messenger RNA expression coincides with the exposure of plants to light. However, how this promotes CO activity is unknown. We show that light stabilizes nuclear CO protein in the evening, whereas in the morning or in darkness the protein is degraded by the proteasome. Photoreceptors regulate CO stability and act antagonistically to generate daily rhythms in CO abundance. This layer of regulation refines the circadian rhythm in CO messenger RNA and is central to the mechanism by which day length controls flowering.     

Plague reservoir species throughout the world

Plague has been known since ancient times as a re-emerging infectious disease, causing considerable socioeconomic burden in regional hotspots. To better understand the epidemiological cycle of the causative agent of the plague, its potential occurrence, and possible future dispersion, one must carefully consider the taxonomy, distribution, and ecological requirements of reservoir-species in relation either to natural or human-driven changes (e.g. climate change or urbanization). In recent years, the depth of knowledge on species taxonomy and species composition in different landscapes has undergone a dramatic expansion, driven by modern taxonomic methods such as synthetic surveys that take into consideration morphology, genetics, and the ecological setting of captured animals to establish their species identities. Here, we consider the recent taxonomic changes of the rodent species in known plague reservoirs and detail their distribution across the world, with a particular focus on those rodents considered to be keystone host species. A complete checklist of all known plague-infectable vertebrates living in plague foci is provided as a Supporting Information table.