Molecular cloning and characterization of a lipoxygenase gene (CsLOX1) from cucumber

Lipoxygenases (LOXs) are non-heme iron enzymes that play crucial roles in many developmental processes during plant life, and defense responses against biotic and abiotic stresses. In this study, a lipoxygenase gene (CsLOX1) was cloned and characterized from cucumber (Cucumis sativus). The coding sequence (CDS) of CsLOX1 was 741 bp, and encoded an 878 amino-acid residue protein, which was predicted to be located in the cytoplasm. CsLOX1 contained the conserved LH2/PLAT and lipoxygenase domains, as well as the representative 38 amino acids motif [His-(X)4-His-(X)4-His-(X)17-His-(X)8-His]. Multiple sequence alignment and phylogenetic analysis indicated that CsLOX1 was closely related to other dicot 9-LOXs and posesess the essential conserved residues involved in the binding of the iron atom. Promoter analysis suggested that several development-, stress-, and hormone-related cis-acting regulatory elements were present in the promoter region of CsLOX1. The function of CsLOX1 was assessed by overexpression it in Arabidopsis, and the transgenic plants were male sterile and displayed obviously increased floral shoots. These results provide some clues for revealing the biological roles of CsLOX1 in cucumber.

Identification, Phylogeny, and Comparative Expression of the Lipoxygenase Gene Family of the Aquatic Duckweed, Spirodela polyrhiza, during Growth and in Response to Methyl Jasmonate and Salt

Lipoxygenases (LOXs) (EC 1.13.11.12) catalyze the oxygenation of fatty acids and produce oxylipins, including the plant hormone jasmonic acid (JA) and its methyl ester, methyl jasmonate (MeJA). Little information is available about the LOX gene family in aquatic plants. We identified a novel LOX gene family comprising nine LOX genes in the aquatic plant Spirodela polyrhiza (greater duckweed). The reduced anatomy of S. polyrhiza did not lead to a reduction in LOX family genes. The 13-LOX subfamily, with seven genes, predominates, while the 9-LOX subfamily is reduced to two genes, an opposite trend from known LOX families of other plant species. As the 13-LOX subfamily is associated with the synthesis of JA/MeJA, its predominance in the Spirodela genome raises the possibility of a higher requirement for the hormone in the aquatic plant. JA-/MeJA-based feedback regulation during culture aging as well as the induction of LOX gene family members within 6 h of salt exposure are demonstrated.

Crude Oil Contamination Enhances the Lipoxygenase Gene Expression in the Green Microalga Scenedesmus dimorphu

Crude oil is a mixture of hydrocarbons, which are mainly toxic to living organisms. Over recent years it has become clear that algae may play a substantial role in the biodegradation of the crude oil harmful hydrocarbons by their dioxygenase system. The present study was conducted to evaluate alterations in the expression levels of lipoxygenase gene (lox) in Scenedesmus dimorphus after exposure to crude oil. The extraction of total RNA was performed by RNX plus reagent. After cDNA synthesis, a qRT-PCR analysis was performed to determine the expression level of the lox gene. The acquired data were analyzed by SPSS Statistics. Based on the obtained results, crude oil treatments (0.02 and 1%) led to a relatively high expression level of lox compared to control conditions. Moreover, incubation time significantly affected the relative expression of this gene in both oil-treated and non-treated algae. The outcomes of this research indicated that S. dimorphus has a high potential for the enhancement of enzymatic activity under crude oil treatment through increased lox expression.