Regulation of jasmonate signaling by reversible acetylation of TOPLESS in Arabidopsis

The plant hormone jasmonate(JA)regulates plant immunity and adaptive growth by orchestrating a genome-wide transcriptional program.Key regulators of JA-responsive gene expression include the master transcription factor MYc2,which is repressed by the conserved Groucho/Tup1-like corepressor TOPLESS(TPL)in the resting state.However,the mechanisms underlying TPL-mediated transcriptional repression of MYc2 activity and hormone-dependent switching between repression and de-repression remainenigmatic.Here,we report the regulation of TPLactivity and JAsignaling byreversibleacetylation of TPL.We found that the histone acetyltransferase GCN5 could mediate TPL acetylation,which enhances its interaction with the NOVEL-INTERACTOR-OF-JAZ(NINJA)adaptor and promotes its recruitment to MYc2 target promoters,facilitating transcriptional repression.Conversely,TPL deacetylation by the histonedeacetylase HDA6 weakens TPL-NINJA interaction and inhibitsTPL recruitmentto MYC2 target promoters,facilitating transcriptional activation.In the resting state,the opposing activities of GCN5 and HDA6 maintain TPL acetylation homeostasis,promoting transcriptional repression activity of TPL.In response to JA elicitation,HDA6 expression is transiently induced,resulted in decreased TPL acetylation and repressor activity,thereby transcriptional activation of MYC2 target genes.Thus,the GCN5-TPL-HDA6 module main tains the homeostasis of acetylated TPL,thereby determining the transcriptional state of JA-responsive genes.Our findings uncovered a mechanism by which the TPL corepressor activity in JA signaling is activelytuned inarapidandreversiblemanner.

Jasmonate signaling makes flowers attractive to pollinators and repellant to florivores in nature

Flowers are required for the Darwinian fitness of flowering plants, but flowers＇ advertisements for pollination services can attract florivores. Previous glasshouse work with Nicotiana attenuata revealed the role of jasmonate （JA） signaling in flower development, advertisement and defense. However, whether JA signaling mediates flowers＇ filtering of floral visitors in nature remained unknown. This field study revealed that silencing JA signaling resulted in flowers that produce less nectar and benzyl acetone, two pollinatorattractive traits. Meanwhile, flowers of defenseless plants were highly attacked by a suite of native herbivores, and damage to buds in native plants correlated negatively with their JA-lle levels.

Response of Rice to Insect Elicitors and the Role of OsJAR1 in Wound and Herbivory-Induced JA-lle Accumulation

Plants produce jasmonic acid （JA） and its amino acid conjugate, jasmonoyI-L-isoleucine （JA-Ile） as major defense signals in response to wounding and herbivory. In rice （Oryza sativa）, JA and JA-Ile rapidly increased after mechanical damage, and this increase was further amplified when the wounds were treated with oral secretions from generalist herbivore larvae, lawn armyworms （Spodoptera mauritia）, revealing for the first time active perception mechanisms of herbivore-associated elicitor（s） in rice. In the rice genome, two OsJAR genes can conjugate JA and lie and form JA-Ile in vitro; however, their function in herbivory- induced accumulation of JA-Ile has not been investigated. By functional characterization of TOS17 retrotransposon-tagged Osjarl plants and their response to simulated herbivory, we show that OsJAR1 is essential for JA-Ile production in herbivore-attacked, field-grown plants. In addition, OsJAR1 was required for normal seed development in rice under field conditions. Our results suggest that OsJAR1 possesses at least two major functions in rice defense and development that cannot be complemented by the additional OsJAR2 gene function, although this gene previously showed overlapping enzyme activity in vitro.

Induction of jasmonic acid biosynthetic genes inhibits Arabidopsis growth in response to low boron

The essential micronutrient boron(B) has key roles in cell wall integrity and B deficiency inhibits plant growth. The role of jasmonic acid(JA) in plant growth inhibition under B deficiency remains unclear. Here,we report that low B elevates JA biosynthesis in Arabidopsis thaliana by inducing the expression of JA biosynthesis genes. Treatment with JA inhibited plant growth and, a JA biosynthesis inhibitor enhanced plant growth, indicating that the JA induced by B deficiency affects plant growth. Furthermore,examination of the JA signaling mutants jasmonate resistant1, coronatine insensitive1-2, and myc2 showed that JA signaling negatively regulates plant growth under B deficiency. We identified a low-B responsive transcription factor, ERF018, and used yeast one-hybrid assays and transient activation assays in Nicotiana benthamiana leaf cells to demonstrate that ERF018 activates the expression of JA biosynthesis genes. ERF018 overexpression(OE)lines displayed stunted growth and up-regulation of JA biosynthesis genes under normal B conditions,compared to Col-0 and the difference between ERF018 OE lines and Col-0 diminished under low B.These results suggest that ERF018 enhances JA biosynthesis and thus negatively regulates plant growth. Taken together, our results highlight the importance of JA in the effect of low B on plant growth.