The Role of Octadecanoids and Functional Mimics in Soybean Defense Responses

Abstract

Oxylipins of the jasmonate pathway and synthetic functional analogs have been analyzed for their elicitor-like activities in an assay based on the induced accumulation of glyceollins, the phytoalexins of soybean (Glycine max L.), in cell suspension cultures of this plant. Jasmonic acid (JA) and its methyl ester showed weak phytoalexin-inducing activity when compared to an early jasmonate biosynthetic precursor, 12-oxo-phytodienoic acid (OPDA), as well as to the bacterial phytotoxin coronatine and certain 6-substituted indanoyl-L-isoleucine methyl esters, which all were highly active. Interestingly, different octadecanoids and indanoyl conjugates induced the accumulation of transcripts of various defense-related genes to different degrees, indicating distinct induction competencies. Therefore, these signaling compounds and mimics were further analyzed for their effects on signal transduction elements, such as the transient enhancement of the cytosolic Ca 2 + concentration and MAP kinase activation, which are known to be initiated by a soybean pathogen-derived ␤-glucan elicitor. In contrast to the ␤-glucan elicitor, none of the other compounds tested triggered these early signaling elements. Moreover, endogenous levels of OPDA and JA in soybean cells were shown to be unaffected after treatment with ␤-glucans. Thus, OPDA and JA, which are functionally mimicked by coronatine and a variety of 6-substituted derivatives of indanoyl-L-isoleucine methyl ester, represent highly efficient signaling compounds of a lipid-based pathway not deployed in the ␤-glucan elicitor-initiated signal transduction.

Transcriptional Profiling of Sorghum Induced by Methyl Jasmonate, Salicylic Acid, and Aminocyclopropane Carboxylic Acid Reveals Cooperative Regulation and Novel Gene Responses

“…Recent work also suggests that SA/ JA coregulation conditions resistance to some pathogens (van Wees et al, 2000;Berrocal-Lobo et al, 2002). The JA precursor OPDA is a potent inducer of defense responses, which are in some cases different than those induced by JA (Fleigmann et al, 2003). The finding that SA greatly increased OPDA production (Laudert and Weiler, 1998) implies that OPDA may be an important component in, or branch of, the SA defense pathway.…”

Review Jasmonates are phytohormones with multiple functions, including plant defense and reproduction

“…Jasmonic acid and MeJA besides the bacterial phytotoxin coronatine (a highly active compound in the defense response) presented weak activity in inducing phytoalexins when compared to 12-OPDA in cell culture (Fliegmann et al, 2003). Potato plants inoculated with the pathogen P. syringae pv.…”

Jasmonic Acid and Its Precursor 12-Oxophytodienoic Acid Control Different Aspects of Constitutive and Induced Herbivore Defenses in Tomato

“…OPDA is much more active than JA/JA-Ile in mechanotransduction (Stelmach et al, 1998;Blechert et al, 1999;Escalante-Pérez et al, 2011) and it sustains resistance of Arabidopsis plants against herbivores and pathogens in absence of JA/JA-Ile (Stintzi et al, 2001;Zhang and Turner, 2008;Stotz et al, 2011). OPDA also elicits the synthesis of diterpenoidderived volatiles in lima bean (Phaseolus lunatus) and the accumulation of phytoalexins in soybean (Glycine max) more efficiently than JA (Koch et al, 1999;Fliegmann et al, 2003). Seed dormancy is regulated by OPDA in Arabidopsis (Dave et al, 2011), and in tomato (Solanum lycopersicum) OPDA rather than JA/JA-Ile is also required for embryo development (Goetz et al, 2012).…”