Another JA/COI1-independent role of OPDA detected in tomato embryo development

Abstract

(+)-7-iso-jasmonoyl isoleucine, the bioactive JA, is involved in most JA-dependent processes mediated by the F-box protein COI1 in a proteasome-dependent manner. However, there is an increasing number of examples, where the precursor of JA biosynthesis, cis-(+)-12-oxophytodienoic acid (OPDA) is active in a JA/COI1-independent manner. Here, we discuss those OPDA-dependent processes, thereby giving emphasis on tomato embryo development. Recent data on seed coat-generated OPDA and its role in embryo development is discussed based on biochemical and genetic evidences.The plant hormone jasmonic acid (JA) was initially detected as its methyl ester in the essential oil of flowers of Jasminum grandiflorum.1 In the sixties and the seventies numerous additional jasmonate compounds were detected preferentially in flowers.2 In the last three decades hydroxylated, glucosylated, sulphated, decarboxylated and carboxylated derivatives as well as JA amino acid conjugates have been identified as plant constituents. Upon wounding there is a rapid accumulation of JA, JA-Ile within some minutes, followed by accumulation of their hydroxylated, carboxylated and glucosylated derivatives. [3][4][5] Some of these JA metabolites occur in flower organs and seeds up to three orders of magnitude higher levels than JA. 6 All Another JA/COI1-independent role of OPDA detected in tomato embryo development 9-11 This metabolic conversion of JA and JA-Ile, respectively, leads to compounds being biologically inactive in some processes such as wounding, where JA and JA-Ile are typically involved as signaling compounds. 6,9,11 In contrast, an O-glycosylated JA derivative is active in leaf movement, 12 and decarboxylated JA, called cis-jasmone, leads to expression of a specific set of genes different from those involved in JA-induced gene expression. 13All these aspects contribute to the questions whether or not the different JA compounds exhibit individual specificity in signaling and which of the metabolic conversion of JA or JA-Ile represents a "switch off" in its signaling cascade.In the last couple of years a similar question was already addressed for the precursor of JA, 12-oxophytodienoic acid (OPDA). Cis-(+)-OPDA is formed by the allene oxide cyclase (AOC)-catalyzed step of JA biosynthesis (Fig. 1) leading to establishment of that enantiomeric structure which is a feature of the naturally occurring JA.7,14 OPDA accumulates upon wounding of leaves usually to higher levels than JA and JA-Ile. 3,4,15 Moreover, a large portion of OPDA is esterified within lipid membranes to numerous compounds. 16,17 These compounds are called arabidopsides due to their exclusive occurrence in the 25 The AOC-catalyzed step in JA biosynthesis is required for OPDA and JA generation. Therefore, the flower phenotype of 35S::AOC-RNAi lines was assumed to be caused by any compound formed downstream of the AOC step. Due to the low seed set of these RNAi lines, however, OPDA and JA levels could not be analyzed.Interestingly, the tomato mutant spr2 has a delay in proper embr...

Defense Responses in Two Ecotypes of Lotus japonicus against Non-Pathogenic Pseudomonas syringae

“…In addition, the activation of JA signaling in MG-20 may not be dependent on classical mediators, since two JAR1 and one COI1 homologues were down-regulated under pathogenic conditions. The existence of a COI1-independent JA pathway has been described in Arabidopsis and tomato [73,74]. …”

Attenuated accumulation of jasmonates modifies stomatal responses to water deficit

“…In the spr2 (suppressor of prosystemin-mediated responses 2; Howe et al , 1996 ) mutant, the lack of a chloroplast fatty acid desaturase in the octadecanoid pathway compromises constitutive JA biosynthesis, severely decreasing leaf ( Li et al , 2003 ) and root ( Tejeda-Sartorius et al , 2008 ) JA levels. Wound-induced JA biosynthesis is also impaired ( Li et al , 2003 ) as is OPDA biosynthesis ( Wasternack et al , 2012 ). Thus spr2 is more generally deficient in both jasmonates and OPDA biosynthesis.…”

Homologs of old yellow enzyme in plants

“…Besides its role in plant stress responses, JA acts as a plantgrowth regulator. It affects a variety of developmental processes such as fruit ripening (Creelman and Mullet, 1997), root growth (Staswick et al, 1992), tendril coiling (Stelmach et al, 1999), tuber formation (Yoshihara et al, 1989), flower development, pollen maturation (Sanders et al, 2000;Stintzi and Browse, 2000), seed development (Wasternack et al, 2012), and senescence (Parthier, 1990). OPDA is the precursor of JA and belongs to an important class of jasmonates.…”

“…Jasmonates such as JA, methyl jasmonate, OPDA, and related cyclopentenones are ubiquitous, lipid-derived compounds with signaling functions in plant development. In addition, they are involved in responses to biotic and abiotic stresses (Wasternack, 2007;Wasternack et al, 2012). Although significant progress has been made towards the understanding of the physiological importance of OPR enzymes, the function of OPRI enzymes in plants remains unclear.…”