Differential Impact of Lipoxygenase 2 and Jasmonates on Natural and Stress-Induced Senescence in Arabidopsis

Abstract

Jasmonic acid and related oxylipins are controversially discussed to be involved in regulating the initiation and progression of leaf senescence. To this end, we analyzed profiles of free and esterified oxylipins during natural senescence and upon induction of senescence-like phenotypes by dark treatment and flotation on sorbitol in Arabidopsis (Arabidopsis thaliana). Jasmonic acid and free 12-oxo-phytodienoic acid increased during all three processes, with the strongest increase of jasmonic acid after dark treatment. Arabidopside content only increased considerably in response to sorbitol treatment. Monogalactosyldiacylglycerols and digalactosyldiacylglycerols decreased during these treatments and aging. Lipoxygenase 2-RNA interference (RNAi) plants were generated, which constitutively produce jasmonic acid and 12-oxo-phytodienoic acid but do not exhibit accumulation during natural senescence or upon stress treatment. Chlorophyll loss during aging and upon dark incubation was not altered, suggesting that these oxylipins are not involved in these processes. In contrast, lipoxygenase 2-RNAi lines and the allene oxid synthase-deficient mutant dde2 were less sensitive to sorbitol than the wild type, indicating that oxylipins contribute to the response to sorbitol stress.

Disruption of OPR7 and OPR8 Reveals the Versatile Functions of Jasmonic Acid in Maize Development and Defense

“…The JA-defective Arabidopsis mutants aos and opr3 did not show altered senescence phenotypes during natural senescence processes or upon dark treatment (He et al, 2002;Schommer et al, 2008). In addition, chlorophyll loss in the leaves during natural senescence and upon dark incubation was not altered in LOX2-RNA interference plants, which exhibited no increased accumulation of JA or OPDA (Seltmann et al, 2010). This uncertainty led us to test whether JA deficiency in opr7 opr8 mutants may have altered the content of other plant hormones reported to have a strong association with leaf senescence.…”

“…Currently, the role for JA in leaf senescence remains unclear, as a number of studies have reported conflicting results (Schenk et al, 2000;He et al, 2002;Castillo and León, 2008;Seltmann The wild-type (WT; [A]) plant showed normal ear shoots and normal outgrowth of ear buds (E). opr7 opr8 double mutant combinations, opr7-5 opr8-2 (B), opr7-5 opr8-3 (C), and opr7-5 opr8-4 (D), displayed multiple elongated ear shoots.…”

Transcriptional Mechanism of Jasmonate Receptor COI1-Mediated Delay of Flowering Time in Arabidopsis

“…Other examples in which different members of a gene family contribute to different aspects of the JA response come from the JA synthesis gene family 13-LIPOXYGENASE. Among the four LOX genes in the Arabidopsis genome (i.e., LOX2, LOX3, LOX4, and LOX6), it is already known that LOX2 is mainly involved in wound-induced JA biosynthesis but has a negligible effect on fertility (Glauser et al, 2009;Seltmann et al, 2010), whereas LOX3 and LOX4 act redundantly to regulate fertility (Caldelari et al, 2011). It is of great interest to identify the JA biosynthesis genes that are specifically involved in the control of flowering.…”

Comprehensive Dissection of Spatiotemporal Metabolic Shifts in Primary, Secondary, and Lipid Metabolism during Developmental Senescence in Arabidopsis

“…Therefore, in order to consider the evidence of specific roles for metabolites in senescence, a more precise analysis of metabolite levels in different tissues and cell types during the process of senescence is required. Although, to date, a number of targeted metabolite profiles, particularly those focused on lipids as seed storage compounds (Yang and Ohlrogge, 2009;Seltmann et al, 2010) and sugars, amino acids, and nutrient ions (Masclaux et al, 2000;Quirino et al, 2001;Stessman et al, 2002;Diaz et al, 2005;Masclaux-Daubresse et al, 2005, 2007Pourtau et al, 2006;Wingler et al, 2006Wingler et al, , 2012, have been generated from maturing and senescing tissues, a broad overview of metabolic changes during senescence, including the interactions between various metabolic pathways, is still lacking. Therefore, we performed a metabolomics study to obtain comprehensive metabolite profiles, including primary and secondary metabolites and lipids, over the course of developmental senescence in rosette leaves before and after bolting and siliques of Arabidopsis in order to investigate the metabolic response and spatiotemporal distribution of metabolites during senescence at the whole-plant level and within single leaves.…”