FeatuDefects in Allene Oxide Synthase and 12-Oxa-Phytodienoic Acid Reductase Alter the Resistance to Pseudomonas syringae and Botrytis cinerea

Jasmonic acid and its methyl ester are signalling molecules involved in regulating development and stress responses in plants. 12-Oxo-phytodienoic acid, a precursor in jasmonic acid biosynthesis, is also biologically active. Both oxylipins accumulate after pathogen infection. To understand the function of 12-oxo-phytodienoic acid vs. jasmonic acid in plant pathogen interactions, the susceptibility of the dde2 mutant, defective in 12-oxo-phytodienoic acid and jasmonic acid biosynthesis and the opr3 mutant, which synthesizes 12-oxo-phytodienoic acid but not jasmonic acid was investigated. dde2 and opr3 were more resistant to Pseudomonas syringae. The effect was stronger in the dde2 mutant as in opr3 indicating that both oxylipins regulate pathogen resistance to P. syringae. dde2 was more susceptible to Botrytis cinerea suggesting that 12-oxo-phytodienoic acid is important in mediating the defence against B. cinerea. Expression of Pr1 and Pr2 was increased in both mutants after mock infiltration but not or only slightly enhanced after P. syringae infection.

Source: Journal of Phytopathology (2006) vol. 154 , p. 740 - 744

Recent developments in biochemistry of the plant lipoxygenase pathway

Lipoxygenase (LOX, EC 1.13.11.12) is a dioxygenase enzyme widespread in aerobic organisms, including plants. The enzyme oxygenates methylene interrupted polyenoic fatty acids, converting them into hydroperoxides. The predominant substrates of LOXs in plants are linoleic and linolenic acids. Specificities of LOX action and availability of enzymes of hydroperoxide metabolism detemine the diversity of the LOX pathway products. Increasing evidence in the literature demonstrates the great physiological importantance of the plant LOX pathway products.

Source: Progress in Lipid Research (1998) vol. 37 , p. 317-352

Divinyl ether synthesis in garlic bulbs

Formation of 13-lipoxygenase-derived divinyl ethers has been described in garlic bulbs. Here, the identification of a cDNA from garlic is described, which encodes for an enzyme that corresponds to divinyl ether synthases (DES). The recombinant protein was expressed in Escherichia coli and shown to metabolize 13-hydroperoxy as well as 9-hydroperoxy linole(n)ic acid to etherole(n)ic and colnele(n)ic acid, respectively. This biochemical feature classifies it as a member of the CYP74C subfamily of cytochrome P-450 enzymes. Product analysis after incubation of purified recombinant enzyme and fatty acid hydroperoxides revealed the formation of a mixture of different cis/trans isomers with one isomer often dominant. RNA blot analyses showed a constitutive expression of DES transcripts predominant in below-ground organs of garlic. By exogenous application of salicylic acid and sorbitol, but not by methyljasmonate, the transcript was also induced in leaves. Whereas the prominent divinyl ether in garlic was the 13-lipoxygenase-derived etheroleic acid, analysis of transgenic Arabidopsis expressing garlic DES showed that 9-lipoxygenase-derived colnelenic acid dominated 24 h after wounding. These data indicate that the product pattern of this DES from garlic depends on the substrate availability and that the enzyme is the first member in the group of 9/13-DES.

Source: J Exp Bot. (2008) vol. 59, p. 907-915

Animals and Plants as National Symbols of Cambodia

1. Kouprey (Bos sauveli) is the National Mammal of Cambodia
2. Giant Ibis (Pseudibis gigantea) is the National Bird of Cambodia
3. Royal Turtle (Batagur baska) is the National Reptile of Cambodia
4. Giant Mekong Barb (Catlocarpio siamensis) is the National Fish of Cambodia
5. Sugar Palm (Borassus flabellifer) is the National Tree of Cambodia
6. Rumdul (Mitrella mesnyi) is the National Flower of of Cambodia
7. Chicken Egg Banana (Musa aromatica) is the National Fruit of Cambodia

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Adapted from Forestry Administration of Cambodia

Best fuel for your workout

Good food choices to fuel your workout include high-carbohydrate, low-fat snacks such as:

- a banana with yogurt;

- a whole-wheat toasted bagel with fruit spread; or

- a quick bowl of instant oatmeal.

After your workout, it’s essential to refuel your body with a carbohydrate-protein blend, such as:

- a peanut butter sandwich;

- a small handful of walnuts or almonds; or

- a fruit smoothie with some protein powder.

Don't forget to drink water before, during and after your workout to avoid dehydration.