CsrA Enhances Cyclic-di-GMP Biosynthesis and Yersinia pestis Biofilm Blockage of the Flea Foregut by Alleviating Hfq-Dependent Repression of the mRNA.

Plague-causing Yersinia pestis is transmitted through regurgitation when it forms a biofilm-mediated blockage in the foregut of its flea vector. This biofilm is composed of an extracellular polysaccharide substance (EPS) produced when cyclic-di-GMP (c-di-GMP) levels are elevated. The Y.

Developmental Genetics of Corolla Tube Formation: Role of the tasiRNA- Pathway and a Conceptual Model.

Over 80,000 angiosperm species produce flowers with petals fused into a corolla tube. The corolla tube contributes to the tremendous diversity of flower morphology and plays a critical role in plant reproduction, yet it remains one of the least understood plant structures from a developmental genetics perspective. Through mutant analyses and transgenic experiments, we show that the tasiRNA- pathway is required for corolla tube formation in the monkeyflower species Loss-of-function mutations in the orthologs of and cause a dramatic decrease in abundance of -derived small RNAs and a moderate upregulation of () and , which lead to inhibition of lateral expansion of the bases of petal primordia and complete arrest of the upward growth of the interprimordial regions, resulting in unfused corollas.

Biovar-related differences apparent in the flea foregut colonization phenotype of distinct Yersinia pestis strains do not impact transmission efficiency.

Background: Yersinia pestis is the flea-transmitted etiological agent of bubonic plague. Sylvatic plague consists of complex tripartite interactions between diverse flea and wild rodent species, and pathogen strains. Transmission by flea bite occurs primarily by the Y.

Putative Horizontally Acquired Genes, Highly Transcribed during Yersinia pestis Flea Infection, Are Induced by Hyperosmotic Stress and Function in Aromatic Amino Acid Metabolism.

While alternating between insects and mammals during its life cycle, , the flea-transmitted bacterium that causes plague, regulates its gene expression appropriately to adapt to these two physiologically disparate host environments. In fleas competent to transmit , low-GC-content genes , and are highly transcribed, suggesting that these genes have a highly prioritized role in flea infection. Here, we demonstrate that , and are transcribed as part of a single polycistronic mRNA comprising the , , and genes.

Co-infection Assay to Determine Yersinia pestis Competitive Fitness in Fleas.

Co-infection refers to the simultaneous infection of a host by multiple pathogenic organisms. Experimental co-infection studies using a mutant and its isogenic wild type have proven to be profoundly sensitive to analysis of pathogen factor mutation-associated fitness effects in in vivo models of infectious disease. Here we discuss the use of such co-infection experiments in studying the interaction between Yersinia pestis and its flea vector to more sensitively determine the critical bacterial determinants for Y.

An in vitro model of intestinal infection reveals a developmentally regulated transcriptome of Toxoplasma sporozoites and a NF-κB-like signature in infected host cells.

Toxoplasmosis is a zoonotic infection affecting approximately 30% of the world's human population. After sexual reproduction in the definitive feline host, Toxoplasma oocysts, each containing 8 sporozoites, are shed into the environment where they can go on to infect humans and other warm-blooded intermediate hosts. Here, we use an in vitro model to assess host transcriptomic changes that occur in the earliest stages of such infections.

Competition between anthocyanin and flavonol biosynthesis produces spatial pattern variation of floral pigments between Mimulus species.

Flower color patterns have long served as a model for developmental genetics because pigment phenotypes are visually striking, yet generally not required for plant viability, facilitating the genetic analysis of color and pattern mutants. The evolution of novel flower colors and patterns has played a key role in the adaptive radiation of flowering plants via their specialized interactions with different pollinator guilds (e.g.

An R2R3-MYB transcription factor regulates carotenoid pigmentation in Mimulus lewisii flowers.

Carotenoids are yellow, orange, and red pigments that contribute to the beautiful colors and nutritive value of many flowers and fruits. The structural genes in the highly conserved carotenoid biosynthetic pathway have been well characterized in multiple plant systems, but little is known about the transcription factors that control the expression of these structural genes. By analyzing a chemically induced mutant of Mimulus lewisii through bulk segregant analysis and transgenic experiments, we have identified an R2R3-MYB, Reduced Carotenoid Pigmentation 1 (RCP1), as the first transcription factor that positively regulates carotenoid biosynthesis during flower development.

Transcriptional control of floral anthocyanin pigmentation in monkeyflowers (Mimulus).

A molecular description of the control of floral pigmentation in a multi-species group displaying various flower color patterns is of great interest for understanding the molecular bases of phenotypic diversification and pollinator-mediated speciation. Through transcriptome profiling, mutant analyses and transgenic experiments, we aim to establish a 'baseline' floral anthocyanin regulation model in Mimulus lewisii and to examine the different ways of tinkering with this model in generating the diversity of floral anthocyanin patterns in other Mimulus species. We find one WD40 and one bHLH gene controlling anthocyanin pigmentation in the entire corolla of M.

Bulk segregant analysis of an induced floral mutant identifies a MIXTA-like R2R3 MYB controlling nectar guide formation in Mimulus lewisii.

The genetic and developmental basis of many ecologically important floral traits (e.g., carotenoid pigmentation, corolla tube structure, nectar volume, pistil and stamen length) remains poorly understood.

Genetic dissection of a major anthocyanin QTL contributing to pollinator-mediated reproductive isolation between sister species of Mimulus.

Prezygotic barriers play a major role in the evolution of reproductive isolation, which is a prerequisite for speciation. However, despite considerable progress in identifying genes and mutations responsible for postzygotic isolation, little is known about the genetic and molecular basis underlying prezygotic barriers. The bumblebee-pollinated Mimulus lewisii and the hummingbird-pollinated M.