Structural Evidence for the Substrate Channeling of Rice Allene Oxide Cyclase in Biologically Analogous Nazarov Reaction

Abstract

Allene oxide cyclase (AOC) is a key enzyme in the jasmonic acid (JA) biosynthetic pathway in plants, during which it catalyzes stereospecific conversion of 12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid (12,13-EOT) to cis(+)-12-oxophytodienoic acid. Here, rice allene oxide cyclase (OsAOC) was localized to the chloroplast and its native oligomeric structure was analyzed by gel electrophoresis in the absence and presence of a protein-crosslinking reagent. The results suggest that OsAOC exists in solution as a mixture of monomers, dimers, and higher order multimers. OsAOC preferentially exists as dimer at room temperature, but it undergoes temperature-dependent partial denaturation in the presence of SDS. A heteromeric 2:1 complex of OsAOC and rice allene oxide synthase-1 (OsAOS1) was detected after cross-linking. The yield of cis(+)-12-oxophytodienoic acid reached maximal saturation at a 5:1 molar ratio of OsAOC to OsAOS1, when OsAOC and OsAOS1 reactions were coupled. These results suggest that the OsAOC dimer may facilitate its interaction with OsAOS1, and that the heteromeric 2:1 complex may promote efficient channeling of the unstable allene oxide intermediate during catalysis. In addition, conceptual similarities between the reaction catalyzed by AOC and Nazarov cyclization are discussed.

Galactolipid and Phospholipid Profile and Proteome Alterations in Soybean Leaves at the Onset of Salt Stress

“…JA, a major phytohormone regulating abiotic stress responses, is important in early responses to osmotic and salt stress ( Fujita et al, 2006 ; Chen et al, 2017 ) and its biosynthesis was triggered by salt in Arabidopsis ( Ishiguro et al, 2001 ; Wang et al, 2015 , 2018 ). AOC affects the rate of flux through the JA biosynthetic pathway ( Yoeun et al, 2018 ). Overexpression of TaAOC1 conferred salt tolerance in wheat ( Zhao et al, 2014 ).…”

TcbZIP60 positively regulates pyrethrins biosynthesis in Tanacetum cinerariifolium

“…In T. cinerariifolium , CHS and AOC are upstream genes that are more likely to become rate-limiting factors for pyrethrins synthesis ( Figure 1A ). AOC is considered to be the first key enzyme in JA synthesis, affecting the overall biosynthesis rate ( Yoeun et al., 2018 ), and CHS is the first key enzyme in the biosynthesis of pyrethrins ( Hu et al., 2018 ). Our results demonstrated that TcbZIP60 could bind to the E-box and G-box cis-elements on the promoters of both TcCHS and TcAOC , and activated the transcription of these genes in vitro .…”

Assessment of Rice Sheath Blight Resistance Including Associations with Plant Architecture, as Revealed by Genome-Wide Association Studies

“…Related to the jasmonic acid pathway, we identified OsAlba7 (acetylation lowers binding affinity protein 7) in the qShB9 region, allene oxide cyclase ( OsAOC ) (Shimizu et al 2013 ; Yoeun et al 2018 ; Yu et al 2020 ) and TIFY10A in the qShB3-2 region, and the duplicate TIFY10B in qShB7 QTL (Ye et al 2009 ). TIFY10A and TIFY10B are part of the JASMONATE-ZIM DOMAIN ( JAZ ) gene subfamily which produces proteins that are key regulators of the jasmonate hormonal response, and these genes are responsive to wounding, abiotic stress and jasmonic acid (Shimizu et al 2013 ; Ye et al 2009 ).…”