A Nitrile-Tagged Raman Sensor for the Ratiometric Detection of Thiols in Live Cells

Most Raman sensors are based on Raman tags linked to bulky aromatic molecules that affect the subcellular localization. Therefore, here, we developed a small ratiometric Raman sensor, ThioRas, to effectively detect thiols in live cells. ThioRas has a nitrile group that serves as a Raman tag for the thia-Michael reaction, and its nitrile signal shifts in the presence of an adjacent double bond. The molecular weight of ThioRas (167) was sufficiently small to allow ThioRas distribution throughout cells. ThioRas and its glutathione adduct were simultaneously detected in various subcellular locations, demonstrating its potential applicability as a Raman tag for ratiometric analysis

Noncanonical Function of a Small-Molecular Virulence Factor Coronatine against Plant Immunity: An <i>In Vivo</i> Raman Imaging Approach

Coronatine (<b>1</b>), a small-molecular virulence factor produced by plant-pathogenic bacteria, promotes bacterial infection by inducing the opening of stomatal pores, the major route of bacterial entry into the plant, via the jasmonate-mediated COI1-JAZ signaling pathway. However, this pathway is also important for multiple plant functions, including defense against wounding by herbivorous insects. Thus, suppression of the COI1-JAZ signaling pathway to block bacterial infection would concomitantly impair plant defense against herbivorous wounding. Here, we report additional, COI1-JAZ-independent, action of <b>1</b> in <i>Arabidopsis thaliana</i> guard cells. First, we found that a stereoisomer of <b>1</b> regulates the movement of <i>Arabidopsis</i> guard cells without affecting COI1-JAZ signaling. Second, we found using alkyne-tagged Raman imaging (ATRI) that <b>1</b> is localized to the endoplasmic reticulum (ER) of living guard cells of <i>Arabidopsis</i>. The use of <i>arc6</i> mutant lacking chloroplast formation was pivotal to circumvent the issue of autofluorescence during ATRI. These findings indicate that <b>1</b> has an ER-related action on <i>Arabidopsis</i> stomata that bypasses the COI1-JAZ signaling module. It may be possible to suppress the action of <b>1</b> on stomata without impairing plant defense responses against herbivores

Design, Synthesis and Biological Activity of 16,17-Dihydroheronamide C and ent-Heronamide C

16,17-Dihydroheronamide C (8) and ent-heronamide C (ent-1) were designed as probes for the mode-of-action analysis of heronamide C (1). These molecules were synthesized by utilizing a highly modular strategy developed in the preceding paper. Evaluation of the antifungal activity of these compounds revealed the exceptional importance of the C16-C17 double bond for the biological activity of heronamide C, and the existence of chiral recognition between heronamide C (1) and cell membrane components