An Uncharacterized Apocarotenoid-Derived Signal Generated in ζ-Carotene Desaturase Mutants Regulates Leaf Development and the Expression of Chloroplast and Nuclear Genes in Arabidopsis.

In addition to acting as photoprotective compounds, carotenoids also serve as precursors in the biosynthesis of several phytohormones and proposed regulatory signals. Here, we report a signaling process derived from carotenoids that regulates early chloroplast and leaf development. Biosynthesis of the signal depends on ζ-carotene desaturase activity encoded by the ζ-CAROTENE DESATURASE (ZDS)/CHLOROPLAST BIOGENESIS5 (CLB5) gene in Arabidopsis thaliana. Unlike other carotenoid-deficient plants, zds/clb5 mutant alleles display profound alterations in leaf morphology and cellular differentiation as well as altered expression of many plastid- and nucleus-encoded genes. The leaf developmental phenotypes and gene expression alterations of zds/clb5/spc1/pde181 plants are rescued by inhibitors or mutations of phytoene desaturase, demonstrating that phytofluene and/or ζ-carotene are substrates for an unidentified signaling molecule. Our work further demonstrates that this signal is an apocarotenoid whose synthesis requires the activity of the carotenoid cleavage dioxygenase CCD4.

US of the eye made easy: a comprehensive how-to review with ophthalmoscopic correlation.

When performed by a trained examiner, ultrasonography (US) of the eye is a useful tool in diagnosing conditions of the ocular globe, especially when combined with ophthalmoscopy. Pathologic conditions of the ocular globe include several usual and unusual entities, most of which may be properly identified at US. For instance, the ocular globe may have an abnormal size or unusual morphologic characteristics. Lesions of the anterior chamber (eg, hyphema), lens (eg, cataract, luxation), and iris or ciliary bodies (eg, cysts) are usually seen at ophthalmoscopy but may also be depicted at US. Vitreous pathologic conditions may demonstrate echoes caused by various entities such as degeneration, asteroid hyalosis, hemorrhage, and infection, and lines are indicative of different types of detachment, including retinal, choroidal, and hyaloid detachment and retinoschisis. Posterior wall masses are usually tumors (eg, melanoma, metastasis, nevus, hemangioma) but may also result from subretinal hemorrhage or granulomas (from tuberculosis or histoplasmosis). Calcifications may be caused by drusen or be nonspecific. Foreign bodies may also be seen. Knowledge of ocular US techniques and protocols and familiarity with normal and pathologic imaging findings are critical in making a correct diagnosis.