Acyl-lipid desaturases are enzymes that convert a C-C single bond into a C=C double bond in fatty acids that are esterified to membrane-bound glycerolipids. Four types of acyl-lipid desaturase, namely DesA, DesB, DesC, and DesD, acting at the Delta12, Delta15, Delta9, and Delta6 positions of fatty acids respectively, have been characterized in cyanobacteria. These enzymes are specific for fatty acids bound to the sn-1 position of glycerolipids. In the present study, we have cloned two putative genes for a Delta9 desaturase, designated desC1 and desC2, from Nostoc species. The desC1 gene is highly similar to the desC gene that encodes a Delta9 desaturase that acts on C18 fatty acids at the sn-1 position. Homologues of desC2 are found in genomes of cyanobacterial species in which Delta9-desaturated fatty acids are esterified to the sn-2 position. Heterologous expression of the desC2 gene in Synechocystis sp. PCC 6803, in which a saturated fatty acid is found at the sn-2 position, revealed that DesC2 could desaturate this fatty acid at the sn-2 position. These results suggest that the desC2 gene is a novel gene for a Delta9 acyl-lipid desaturase that acts on fatty acids esterified to the sn-2 position of glycerolipids.
Most plant pathologists know certain algae can be used as gelling agents in culture media. Pathologists practicing in tropical or subtropical environments also know that some algae damage plants. The five genera in the order Trentepohliales (Chlorophyta) are unique and fascinating. Among other characteristics, they are subaerial, bright orange to red in color, and one genus, Cephaleuros, is a plant pathogen while another, Stomatochroon, is a space parasite. Cephaleuros causes algal spot and includes 17 accepted species. Of these, 13 develop between the cuticle and the epidermis of their hosts and four grow intercellularly. The latter are especially damaging, causing chlorosis and branch dieback. Zoospores and gametes germinate on plant surfaces during the rainy season and probably penetrate through breaks in the host cuticle. Their filamentous growth forms thalli that produce sporangiophores and spherical gametangia the following year. Several species of Cephaleuros have a broad host range and though their damage is usually superficial, it can be economically important on certain crops. Plant stress is the greatest predisposing factor to this algal disease. Management includes providing plants with sufficient moisture and nutrients, modifying cultural and harvesting practices, and planting resistant cultivars when available.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.