Oxylipins Produced by the 9-Lipoxygenase Pathway inArabidopsisRegulate Lateral Root Development and Defense Responses through a Specific Signaling Cascade

Abstract

Arabidopsis thaliana seedling growth with pure oxylipins resulted in root waving, loss of root apical dominance, and decreased root elongation. 9-Hydroxyoctadecatrienoic acid (9-HOT) was a potent inducer of root waving. Studies with noxy2 (for nonresponding to oxylipins2), a new 9-HOT-insensitive mutant, and coronatine insensitive1-1 (jasmonateinsensitive) revealed at least three signaling cascades mediating the oxylipin actions. Treatment with 9-HOT resulted in a reduction in lateral roots and an increase in stage V primordia. Roots showed strong 9-lipoxygenase (9-LOX) activity, and root primordia expressed 9-LOX genes. These results, along with findings that noxy2 and mutants with defective 9-LOX activity showed increased numbers of lateral roots, suggest that 9-HOT, or a closely related 9-LOX product, is an endogenous modulator of lateral root formation. Histochemical and molecular analyses revealed that 9-HOT activated events common to development and defense responses. A subset of 9-HOT-responding root genes was also induced in leaves after 9-HOT treatment or pathogen inoculation. The results that noxy2 displayed altered root development, enhanced susceptibility to Pseudomonas, and reduced the activation of 9-HOT-responding genes are consistent with mechanistic links among these processes. The nature of the changes detected suggests that oxylipins from the 9-LOX pathway function in cell wall modifications required for lateral root development and pathogen arrest.

9-Lipoxygenase-derived oxylipins activate brassinosteroid signaling to promote cell wall-based defense and limit pathogen infection

“…Our previous studies of 9-LOX derivative action indicated their role as inducers of cell wall modifications and root waving (Vellosillo et al, 2007). Characterization of noxy mutants showed that the 9-LOX pathway participates in signaling cell wall damage (Vellosillo et al, 2013).…”

“…We previously showed the action of 9-LOX derivatives as inducers of cell wall changes, including the formation of callose deposits (Vellosillo et al, 2007). As 9-HOT and 9-KOT activate BR signaling, we tested whether the callose formation activity of these oxylipins is mediated by the activation of BR signaling.…”

“…Analyses of the signaling processes that mediate the action of 9-LOX derivatives indicated their role as regulators of root development and defense responses via a (+)-7-iso-jasmonic acid-independent pathway that might be involved in cell wall modification (Vellosillo et al, 2007). Studies using nonresponding to oxylipins (noxy) mutants with an impaired response to the 9-LOX product 9-hydroxyoctadecatrienoic acid (9-HOT) showed that the 9-LOX signaling defect frequently coincides with enhanced insensitivity to isoxaben (Vellosillo et al, 2013), an herbicide that inhibits cellulose synthesis and triggers cell wall repair responses (Manfield et al, 2004;Hamann et al, 2009).…”

The Reductase Activity of the Arabidopsis Caleosin RESPONSIVE TO DESSICATION20 Mediates Gibberellin-Dependent Flowering Time, Abscisic Acid Sensitivity, and Tolerance to Oxidative Stress

“…FAOHs also accumulate during oxidative stress, when their functions are still elusive (op den Camp et al, 2003;Montillet et al, 2004). Besides their roles in defensive responses, FAOHs are involved in signaling pathways controlling physiological processes such as the regulation of lateral root development (Vellosillo et al, 2007).…”

Accumulation of 9- and 13-KODEs in response to jasmonic acid treatment and pathogenic infection in rice

“…Treatment of Arabidopsis leaves with 9-hydroxyoctadecatrienoic acid (9-HOT) provoked the accumulation of callose, as well as the production of ROS, indicating a role of this oxylipin in defense responses. 21) Colneleic and colnelenic acids are unstable divinyl fatty acids that are considered to be synthesized from linoleic and linolenic acids, respectively, by oxidative reactions by a 9-LOX. These compounds were shown to be pathogen inducible and inhibitory to Phytophthora infestans in potato (Solanum tuberosum) leaves and thus were suggested to function as phytoalexins.…”