Light-induced stomatal opening in Arabidopsis is negatively regulated by chloroplast-originated OPDA signaling.

Stomatal movement is orchestrated by diverse signaling cascades and metabolic activities in guard cells. Light triggers the opening of the pores through the phototropin-mediated pathway, which leads to the activation of plasma membrane H+-ATPase and thereby facilitates potassium accumulation through Kin+ channels. However, it remains poorly understood how phototropin signaling is fine-tuned to prevent excessive stomatal opening and consequent water loss. Here, we show that the stomatal response to light is negatively regulated by 12-oxo-phytodienoic acid (OPDA), an oxylipin metabolite produced through enzymatic oxygenation of polyunsaturated fatty acids (PUFAs). We identify a set of phospholipase-encoding genes, phospholipase (PLIP)1/2/3, which are transactivated rapidly in guard cells upon illumination in a phototropin-dependent manner. These phospholipases release PUFAs from the chloroplast membrane, which is oxidized by guard-cell lipoxygenases and further metabolized to OPDA. The OPDA-deficient mutants had wider stomatal pores, whereas mutants containing elevated levels of OPDA showed the opposite effect on stomatal aperture. Transmembrane solute fluxes that drive stomatal aperture were enhanced in lox6-1 guard cells, indicating that OPDA signaling ultimately impacts on activities of proton pumps and Kin+ channels. Interestingly, the accelerated stomatal kinetics in lox6-1 leads to increased plant growth without cost in water or macronutrient use. Together, our results reveal a new role for chloroplast membrane oxylipin metabolism in stomatal regulation. Moreover, the accelerated stomatal opening kinetics in OPDA-deficient mutants benefits plant growth and water use efficiency.

A Sphingosine-type cerebroside in Clavicorona pyxidata induce fruit body formation.

Clavicorona pyxidata is a wild edible and medicinal mushroom that is rich in bioactive natural products and has thus been extensively used as traditional medicine in China. The present study has determined that the organic crude extract prepared from a fermented culture of C. pyxidata imparted auto-inhibitory effects on mycelial growth and then induced the formation of fruiting bodies. By monitoring bioactivity, one compound was isolated via successive chromatography over silica gel, Sephadex LH-20, and Cl8-reversed phase silica gel and was identified as a known sphingosine-type cerebroside by nuclear magnetic resonance (NMR) and physicochemical data, namely, (4E, 8E)-N-D-2'-hydroxypalmitoyl-1-O-ß-D-glucopyranosyl-9-methyl-4,8-sphingadienine. The application of this cerebroside at a concentration of 200 µg/disc paper resulted in the inhibition of aerial hyphal growth of C. pyxidata. The findings of the present study indicated that this C. pyxidata cerebroside is a fruiting body-inducing substance (FIS).

Gunnilactams A-C, Macrocyclic Tetralactams from the Mycelial Culture of the Entomogenous Fungus Paecilomyces gunnii.

Three novel macrocyclic tetralactams, gunnilactam A (1), gunnilactam B (2), and gunnilactam C (3), were isolated from the submerged fermentation broth of Paecilomyces gunnii, an entomogenous fungus identified as the anamorph of Cordyceps gunnii. Their structures were determined using NMR data, HREIMS, and single-crystal X-ray crystallography. Gunnilactam A exhibited selective cytotoxic activity against human prostate cancer C42B cells with an IC50 value of 5.4 µM.