Jasmonate Precursor Biosynthetic Enzymes LOX3 and LOX4 Control Wound-Response Growth Restriction

Abstract

Wound-response plant growth restriction requires the synthesis of potent mediators called jasmonates (JAs). Four 13-lipoxygenases (13-LOXs) produce JA precursors in Arabidopsis (Arabidopsis thaliana) leaves, but the 13-LOXs responsible for growth restriction have not yet been identified. Through loss-of-function genetic analyses, we identified LOX3 and LOX4 as the principal 13-LOXs responsible for vegetative growth restriction after repetitive wounding. Additional genetic studies were carried out in the gain-offunction fatty acid oxygenation 2 (fou2) mutant that, even when undamaged, shows JA-dependent leaf growth restriction. The fou2 lox3 lox4 triple mutant suppressed the fou2 JA-dependent growth phenotype, confirming that LOX3 and LOX4 function in leaf growth restriction. The fou2 mutation affects the TWO PORE CHANNEL1 (TPC1) ion channel. Additional genetic approaches based on this gene were used to further investigate LOX3 function in relation to leaf growth. To activate LOX3-dependent JA production in unwounded plants, we employed hyperactive TPC1 variants. Expression of the TPC1DCa i variant in phloem companion cells caused strongly reduced rosette growth in the absence of wounding. Summarizing, in parallel to their established roles in male reproductive development in Arabidopsis, LOX3 and LOX4 control leaf growth rates after wounding. The process of wound-response growth restriction can be recapitulated in unwounded plants when the LOX3 pathway is activated genetically using a hyperactive vacuolar cation channel.

Breaking Bad News: Dynamic Molecular Mechanisms of Wound Response in Plants

“…A key function of JAs produced in damaged organs is to travel systemically across tissues in order to reprogram future growth and optimize plant defense strategies ( Huot et al, 2014 ; Guo et al, 2018 ; Ballaré and Austin, 2019 ). Upon damage, plants tightly regulate biosynthesis, transport, and catabolism of JAs ( Browse, 2009 ; Chini et al, 2016 ; Howe et al, 2018 ; Fernández-Milmanda et al, 2020 ; Yang et al, 2020 ). JA biosynthesis in Arabidopsis depends on LOX2, LOX3, LOX4, and LOX6.…”

“…JA biosynthesis in Arabidopsis depends on LOX2, LOX3, LOX4, and LOX6. Each of these LOXs contribute in a different way to regulate JA biosynthesis and transport upon wounding ( Chauvin et al, 2013 , 2016 ; Grebner et al, 2013 ; Yang et al, 2020 ). LOX2 is expressed throughout soft aerial tissues, whereas LOX3, LOX4 , and LOX6 are expressed in the phloem and xylem of leaves ( Chauvin et al, 2013 , 2016 ).…”

“…Upon wounding, LOX6 participates in the radial export of JAs from the leaf vasculature to the blade ( Gasperini et al, 2015 ). It was recently suggested that LOX3 and LOX4 repress leaf growth upon wounding by acting on stem cell populations that determine the rate of leaf primordia development ( Yang et al, 2020 ). Furthermore, the activity of LOX3 and LOX4 in leaf growth is related to the vacuolar cation channel TPC1 through a mechanism that remains unclear ( Bonaventure et al, 2007 ; Yang et al, 2020 ).…”

To Grow or Not to Grow: Specific Lipoxygenases Control Wound-Induced Growth Restriction

“…The fou2 mutant harbors a mutation in the putative voltage sensor of the TWO PORE CHAN-NEL1 gene, which encodes a Ca 21 -permeant nonselective cation channel. Yang et al (2020) found that the severe JA-induced growth inhibition in fou2 is largely suppressed by mutations in LOX3 and LOX4. Collectively, these data reveal the roles of LOX3 and LOX4 in rosette growth and suggest, strikingly, that the stunted and bonsai-like wound phenotypes could be recapitulated through genetic activation of 13-LOXs in the absence of wounding (Fig.…”

“…Furthermore, to test if the bonsai-like phenotype could be genetically phenocopied in unwounded tissues, Yang et al (2020) investigated the relevance of LOX3 activation in phloem tissue, since LOX3 promoter activity spans the xylem and phloem and both these tissues are known to play major roles in leaf-to-leaf signaling (Chauvin et al, 2016;Nguyen et al, 2018). To accomplish this, Yang et al (2020) designed a novel and elegant system where they expressed different variants of the TCP1 protein, under a phloem-specific promoter, and introduced it in the lox quadruple and triple mutant backgrounds with and without a functional LOX3. Phenotypic and biochemical analyses revealed that expressing a hyperactive version of TCP1 genetically activates LOX3-dependent JA production and strongly constrains rosette growth in the absence of wounding (Fig.…”