ALLENE OXIDE SYNTHASE and HYDROPEROXIDE LYASE, Two Non-Canonical Cytochrome P450s in Arabidopsis thaliana and Their Different Roles in Plant Defense

Abstract

The channeling of metabolites is an essential step of metabolic regulation in all living organisms. Multifunctional enzymes with defined domains for metabolite compartmentalization are rare, but in many cases, larger assemblies forming multimeric protein complexes operate in defined metabolic shunts. In Arabidopsis thaliana, a multimeric complex was discovered that contains a 13-lipoxygenase and allene oxide synthase (AOS) as well as allene oxide cyclase. All three plant enzymes are localized in chloroplasts, contributing to the biosynthesis of jasmonic acid (JA). JA and its derivatives act as ubiquitous plant defense regulators in responses to both biotic and abiotic stresses. AOS belongs to the superfamily of cytochrome P450 enzymes and is named CYP74A. Another CYP450 in chloroplasts, hydroperoxide lyase (HPL, CYP74B), competes with AOS for the common substrate. The products of the HPL reaction are green leaf volatiles that are involved in the deterrence of insect pests. Both enzymes represent non-canonical CYP450 family members, as they do not depend on O2 and NADPH-dependent CYP450 reductase activities. AOS and HPL activities are crucial for plants to respond to different biotic foes. In this mini-review, we aim to summarize how plants make use of the LOX2–AOS–AOC2 complex in chloroplasts to boost JA biosynthesis over volatile production and how this situation may change in plant communities during mass ingestion by insect pests.

Comparative Transcriptomic Analysis Revealed Complex Molecular Mechanisms Underlying Pests, Pathogens Resistance and Seed Development in Wild and Cultivated Blackgram

“…The bHLH transcription factor was also up-regulated which imparted immunity to viruses such as tomato yellow leaf curl virus [40] and in cotton leaf curl disease (CLCuD) stress [41]. Hydroperoxidelyase transcript ( HPL, CYP74B ) was found up-regulated which is involved in biosynthesis of jasmonic acid and green leaf volatiles that are deterrents to insects/pests [42]. RNA-Seq results showed basal level over-expression of anti-insect and anti-pathogenic compounds such as acid phosphatase, thaumatin like proteins, trypsin inhibitor/miraculin, vicilin and 7s globulin.…”

Studying Gene Expression in Irradiated Barley Cultivars: PM19L-like and CML31-like Expression as Possible Determinants of Radiation Hormesis Effect

“…Several evidence confirming jasmonic acid (JA) signaling involvement in responses to ionizing radiation were found in this work. In plants, the hormone jasmonic acid and its derivatives regulate plant response to biotic and abiotic stressors [20,21]. Jasmonates are also associated with the formation of a radiation-induced bystander effect in plants [22].…”

“…While the DIOX6 homologue inactivates jasmonate, AOS2 is a homologue of AT5G42650, which encodes a member of the cytochrome P450 gene family that functions as an allene oxide synthase. This enzyme catalyzes dehydration of the hydroperoxide to an unstable allene oxide in the JA biosynthetic pathway [21]. In roots of γ-stimulated cultivars Fox 1 and Ratnik, the expression of AOS2 homologue is enhanced.…”

Optimizing the Production of Recombinant Hydroperoxide Lyase in Escherichia coli Using Statistical Design

“…Hydroperoxide lyase (HPL) is a membrane-bound enzyme mainly distributed in higher plants, algae, and fungi [1][2][3]. HPL is involved in the lipoxygenase (LOX) pathway, which is a lipid oxidation pathway activated in response to biotic or abiotic stress, or during various plant stages development, to produce phyto-oxylipins acting as defense and signaling molecules [4][5][6][7][8][9][10][11][12]. In this pathway, LOX first catalyzes the oxygenation of polyunsaturated fatty acids (PUFAs), such as linoleic or α-linolenic acids, to produce corresponding hydroperoxides [4,13,14].…”