Oxylipin-specific cytochrome P450s (CYP74s) inLotus japonicus: their implications in response to mechanical wounding and nodule formation

Abstract

Plant oxylipins are involved in defense responses against pathogens or herbivores. Each oxylipin compound exerts its distinctive physiological function. The ability of many legumes to fix nitrogen with rhizobia gives them special importance in natural environments and agriculture. It has been postulated that oxylipins are somehow related to symbiosis; however, this is still a controversial issue. In this study, we isolated five genes at the branching point of the oxylipin pathway in Lotus japonicus, and their biochemical functions were identified as allene oxide synthases (AOSs), 13-hydroperoxide lyase (13HPL), and 9/13-HPLs. When the leaves were mechanically wounded, AOS and 9/13HPL were upregulated in leaves and roots, respectively, from which their implications in wound response were suggested. When the plants were inoculated with rhizobia, no big change in the expression levels of genes was found. When high N was supplied to the nodulated plants, the number of nodules decreased, and simultaneously, AOS in the leaves was downregulated. Significance of AOS in response to the N status in the plants was suggested.

Biochemical characterization of allene oxide synthases from the liverwort Marchantia polymorpha and green microalgae Klebsormidium flaccidum provides insight into the evolutionary divergence of the plant CYP74 family

“…We previously reported the biosynthesis of C6 volatiles and allene oxides from fatty acid HPOs by CYP74 enzymes such as AOS and HPL in barley, tomato, cucumber, and Lotus japonicas (Koeduka et al 2003;Matsui et al 2000a, b;Yanagi et al 2011). Although considerable information is available on oxylipins and their biosynthetic enzymes in angiosperms, our understanding of CYP74 enzymes in Marchantiophyta and Charophyta is limited.…”

“…Allene oxide synthases reactions were performed and the reaction products were analyzed as described (Koeduka et al 2003;Yanagi et al 2011). Fatty acid hydroperoxide decomposition activity was determined by measuring the decrease in absorbance at 234 nm derived from the substrate-conjugated diene-hydroperoxide chromophore.…”

Natural elicitors, effectors and modulators of plant responses

“…262 The relationship between oxylipins synthesis and nodule formation has been recently demonstrated. 263 1298 | Nat. Prod.…”

Alleviating the inhibitory effect of salinity stress on nod gene expression in Rhizobium tibeticum – fenugreek (Trigonella foenum graecum) symbiosis by isoflavonoids treatment

“…Flavonoids and oxylipin play a crucial role as signal molecules in promoting the formation of nodules by symbiotic bacteria commonly known as rhizobia (Yanagi et al 2011). Exudates from sprouted seeds can be used as activators of PnodA-lacZ fusion in rhizobia (Maj et al 2010).…”