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Plants are constantly exposed to volatile organic compounds (VOCs) that are released during plant-plant communication, within-plant self-signaling, and plant-microbe interactions. Therefore, understanding VOC perception and downstream signaling is vital for unraveling the mechanisms behind information exchange in plants, which remain largely unexplored. Using the hormone-like function of volatile terpenoids in reproductive organ development as a system with a visual marker for communication, we demonstrate that a petunia karrikin-insensitive receptor, PhKAI2ia, stereospecifically perceives the (−)-germacrene D signal, triggering a KAI2-mediated signaling cascade and affecting plant fitness. This study uncovers the role(s) of the intermediate clade of KAI2 receptors, illuminates the involvement of a KAI2ia-dependent signaling pathway in volatile communication, and provides new insights into plant olfaction and the long-standing question about the nature of potential endogenous KAI2 ligand(s). [ABSTRACT FROM AUTHOR]

Mycobacterium tuberculosis causes epidemic levels of tuberculosis each year and more strains of the disease are becoming resistant to the medications used to treat it. Alanine racemase is a convenient target for new drug candidates for tuberculosis as this enzyme is not found in human cells and in M. tuberculosis is only active when in the dimer form. To elucidate the dimerization process, the equilibrium association constants for monomer-dimer equilibrium were determined using high-performance size-exclusion liquid chromatography in a variety of mobile phases. Alanine racemase appeared to be a high-equilibrium association constant dimer in all mobile phases. The degree of dimerization was sensitive to pH and solution composition; phosphate decreases the fraction of alanine racemase dimers. These findings will be useful in designing new antibiotics that target alanine racemases. [ABSTRACT FROM AUTHOR]