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Allene oxide synthase (AOS) is a key enzyme of the jasmonic acid (JA) signaling pathway. The AOS gene was previously found to be upregulated in an Asian chestnut species resistant to infection by the oomycete Phytophthora cinnamomi ( Castanea crenata ), while lower expression values were detected in the susceptible European chestnut ( Castanea sativa ). Here, we report a genetic and functional characterization of the C. crenata AOS (CcAOS) upon its heterologous gene expression in a susceptible ecotype of Arabidopsis thaliana , which contains a single AOS gene. It was found that Arabidopsis plants expressing CcAOS delay pathogen progression and exhibit more vigorous growth in its presence. They also show upregulation of jasmonic acid and salicylic acid-related genes. As in its native species, heterologous CcAOS localized to plastids, as revealed by confocal imaging of the CcAOS-eGFP fusion protein in transgenic Arabidopsis roots. This observation was confirmed upon transient expression in Nicotiana benthamiana leaf epidermal cells. To further confirm a specific role of CcAOS in the defense mechanism against the pathogen, we performed crosses between transgenic CcAOS plants and an infertile Arabidopsis AOS knockout mutant line. It was found that plants expressing CcAOS exhibit normal growth, remain infertile but are significantly more tolerant to the pathogen than wild type plants. Together, our results indicate that CcAOS is an important player in plant defense responses against oomycete infection and that its expression in susceptible varieties may be a valuable tool to mitigate biotic stress responses.

The allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches of the oxylipin pathway, which underlie the production of jasmonates and aldehydes, respectively, function in plant responses to a range of stresses. Regulatory crosstalk has been proposed to exist between these two signaling branches; however, there is no direct evidence of this. Here, we identified and characterized a jasmonic acid (JA) overproduction mutant, cea62, by screening a rice T-DNA insertion mutant library for lineages that constitutively express the AOS gene. Map-based cloning was used to identify the underlying gene as hydroperoxide lyase OsHPL3. HPL3 expression and the enzyme activity of its product, (E)-2-hexenal, were depleted in the cea62 mutant, which resulted in the dramatic overproduction of JA, the activation of JA signaling, and the emergence of the lesion mimic phenotype. A time-course analysis of lesion formation and of the induction of defense responsive genes in the cea62 mutant revealed that the activation of JA biosynthesis and signaling in cea62 was regulated in a developmental manner, as was OsHPL3 activity in the wild-type plant. Microarray analysis showed that the JA-governed defense response was greatly activated in cea62 and this plant exhibited enhanced resistance to the T1 strain of the bacterial blight pathogen Xanthomonasoryzaepvoryzae (Xoo). The wounding response was attenuated in cea62 plants during the early stages of development, but partially recovered when JA levels were elevated during the later stages. In contrast, the wounding response was not altered during the different developmental stages of wild-type plants. These findings suggest that these two branches of the oxylipin pathway exhibit crosstalk with regards to biosynthesis and signaling and cooperate with each other to function in diverse stress responses.

Background Adams-Oliver syndrome (AOS) is a rare developmental disorder, and the DOCK6 gene is an identified AOS gene. This report highlights the prenatal diagnosis of AOS-2 by ultrasonography and genetic testing. Methods A growth-restricted fetus with bilateral ventriculomegaly, paraventricular calcifications, and ventricular septal defect underwent trio-whole-exome sequencing (trio-WES). Functional validation of the splice-altering variant was performed via minigene assays and protein structural modeling. Results Trio-WES revealed compound heterozygous DOCK6 variants: a paternal frameshift (c.3190_3191del; p. Leu1064Valfs60) and a maternal splice-site variant (c.3241-1G > T). Minigene assays demonstrated that c.3241-1G > T caused intron 26 retention (486 bp), introducing a premature termination codon (p. Val1081Glufs37). Structural modeling confirmed the loss of critical DHR2 domains in both truncated proteins. Conclusions This study expands the mutational spectrum of DOCK6 and underscores the importance of combining prenatal imaging with functional genomics for early diagnosis of AOS2.

We report functional genomics studies of a CYP74 rubber particle protein from , commonly called guayule. Previously identified as an allene oxide synthase (AOS), this CYP74 constitutes the most abundant protein found in guayule rubber particles. Transgenic guayule lines with gene expression down-regulated by RNAi ( ) exhibited strong phenotypes that included agricultural traits conducive to enhancing rubber yield. lines had higher leaf and stem biomass, thicker stembark tissues, increased stem branching and improved net photosynthetic rate. Importantly, the rubber content was significantly increased in lines compared to the wild-type (WT), vector control and overexpressing ( ) lines, when grown in controlled environments both in tissue-culture media and in greenhouse/growth chambers. Rubber particles from plants consistently had less AOS particle-associated protein, and lower activity (for conversion of 13-HPOT to allene oxide). Yet plants with downregulated showed higher rubber transferase enzyme activity. The increase in biomass in lines was associated with not only increases in the rate of photosynthesis and non-photochemical quenching (NPQ), in the cold, but also in the content of the phytohormone SA, along with a decrease in JA, GAs, and ABA. The increase in biosynthetic activity and rubber content could further result from the negative regulation of expression by high levels of salicylic acid in lines and when introduced exogenously. It is apparent that AOS in guayule plays a pivotal role in rubber production and plant growth.

Allene oxide synthase (AOS) and hydroperoxide lyase (HPL), members of the CYP74 gene family, are branches of the oxylipin pathway and play vital roles in plant responses to a number of stresses. In this study, four HPL genes and one AOS gene were identified in the watermelon genome, which were clustered into three subfamilies (CYP74A, CYP74B and CYP74C). Sequence analysis revealed that most HPL and AOS proteins from various plants contain representative domains, including Helix-I region, Helix-K region (ExxR) and Heme-binding domain. A number of development-, stress-, and hormone-related cis-elements were found in the promoter regions of the ClAOS and ClHPL genes, and the detected ClAOS and ClHPL genes were differentially expressed in different tissues and fruit development stages, as well as in response to various hormones. In addition, red light could enhance the expression of ClAOS in root-knot nematode-infected leaves and roots of watermelon, implying that ClAOS might play a primary role in red light-induced resistance against root-knot nematodes. These findings lay a foundation for understanding the specific function of CYP74 genes in watermelon.

The Arabidopsis thaliana (L.) Heynh. mutant delayed-dehiscence2-2 (dde2-2) was identified in an En1/Spm1 transposon-induced mutant population screened for plants showing defects in fertility. The dde2-2 mutant allele is defective in the anther dehiscence process and filament elongation and thus exhibits a male-sterile phenotype. The dde2-2 phenotype can be rescued by application of methyl jasmonate, indicating that the mutant is affected in jasmonic acid biosynthesis. The combination of genetic mapping and a candidate-gene approach identified a frameshift mutation in the ALLENE OXIDE SYNTHASE (AOS) gene, encoding one of the key enzymes of jasmonic acid biosynthesis. Expression analysis and genetic complementation of the dde2-2 phenotype by overexpression of the AOS coding sequence confirmed that the male-sterile phenotype is indeed caused by the mutation in the AOS gene.

Allene oxide synthase (AOS; hydroperoxide dehydratase; EC 4.2.1.92) catalyzes the first step in the biosynthesis of jasmonic acid from lipoxygenase-derived hydroperoxides of free fatty acids. Using the AOS cDNA from tomato (Lycopersicon esculentum), in which the role of jasmonic acid in wound-induced defense gene activation has been best described, we examined the kinetics of AOS induction in response to wounding and elicitors, in parallel with that of the wound-inducible PIN II (proteinase inhibitor II) gene. AOS was induced in leaves by wounding, systemin, 12-oxophytodienoic acid, and methyl jasmonate. The levels of AOS mRNA started declining by 4 h after induction, whereas the levels of PIN II mRNA continued to increase up to 20 h after induction. Salicylic acid inhibited AOS and PIN II expression, and the addition of 12-oxophytodienoic acid or methyl jasmonate did not prevent the inhibition of PIN II expression in the presence of salicylic acid. Ethylene induced the expression of AOS, but the presence of ethylene alone did not produce an optimal induction of PIN II. The addition of silver thiosulfate, an ethylene action inhibitor, prevented the wound-induced expression of both AOS and PIN II. Products of hydroperoxide lyase affected neither AOS nor PIN II, but induced expression of prosystemin. Based on these results, we propose an updated model for defense gene activation in tomato.

[...]the cloning and expression analysis of AOS gene has attracted increasing attention in recent years. lilium is a genus of herbaceous flowering plants, all with large prominent flowers. The structure, function and expression of AOS gene in Lilium 1 Siberia ' have not been reported so far. [...]this gene was cloned and analyzed bioinformatically, to provide a theoretical basis for breeding and improvement of Lilium · Siberia'. [...]a DNA fragment of about 1 800 bp was amplified by PCR (Fig. 2) , gel-purified, and sequenced. L2\"_ found that the expression of JA synthesis related genes such as AOS is affected by WRKY3 and WRK.Y6 in tobacco, These WRKY transcription factors can promote the accumulation of JA and JA-ile in plants by regulating the expression of AOS gene. [...]WRKY and other transcription factors can be considered as the starting point for exploring the regulatory effect of AOS gene during JA synthesis and secondary metabolism in plants.

Allene oxide synthase (AOS) is the first committed step in the biosynthetic pathway of Jasmonate. In this study, a full-length cDNA of AOS gene (named as AaAOS ) was cloned from Artemisia annua . The gene was 1891 bp in size containing an open reading frame (1581 bp) encoding 526 amino acids. Comparative and bioinformatic analysis revealed that the deduced protein of AaAOS was highly homologous to AOSs from other plant species. Phylogenetic analysis indicated that the protein of AaAOS belonged to the dicotyledonous group, which was consistent with the category of A. annua . Southern blot analysis revealed that it was a low-copy gene. Quantitative Real-time PCR (qRT-PCR) analysis showed that AaAOS mRNA accumulated most abundantly in leaves and flowers. The qRT-PCR analysis revealed that MeJA, ABA and ethylene treatments significantly enhanced AaAOS transcript expression.

We used the cDNA-AFLP method to analyze gene expression changes of two sorghum lines with different resistance to aphids during aphid infestation. We identified 65 differential display fragments, including 6 sequences that were different between resistant and susceptible mRNA pools without aphid induction. The amplified fragments were sequenced to identify the corresponding genes. A total of 23 sequences were identified. This included 2 sequences (sequences 1 and 4) that are expressed ubiquitously in the aphid-resistant cultivar but are only expressed during infestation of the sensitive cultivar. Sequence searches by BLASTx and BLASTn software showed that sequence 1 was 97% (194/199) similar to the AOS gene from Oryza sativa and that sequence 4 was 98% (298/304) similar to the LOX-2 mRNA from Oryza sativa. Other sequences were divided into 9 functional classes involved in plant resistance to disease and insect infestation. The expression of sequence 4 was evaluated by real-time PCR. The results show that the transcript of sequence 4 was induced by aphid and the expression was upregulated, but the amount of sequence 4 transcript in resistant plants was higher than in susceptible plants.