The functions of jasmonic acid (JA) in plant defense and development are controlled by the JAZ family of repressor proteins. In this issue of Molecular Cell, Hu et al. (2013) identified JAV1 as a repressor protein in the JA pathway that enables the plant to defend against necrotrophic pathogens and herbivorous insects apparently without influencing plant growth and development.

Several lines of evidence indicate that phospholipase A(2) (PLA(2)) plays a crucial role in plant cellular responses through production of linolenic acid, the precursor of jasmonic acid, from membrane phospholipids. Here we report the purification and characterization of a 48-kD PLA(2) from the membrane fractions of leaves of broad bean (Vicia faba). The plant PLA(2) was purified to near homoge...

When grafting or wounding disconnects stem tissues, new tissues are generated to restore the lost connection. In this study, the molecular mechanism of such healing was elucidated in injured stems of Arabidopsis. Soon after the inflorescence stems were incised, the pith cells started to divide. This process was strongly inhibited by the elimination of cauline leaves, shoot apices, or lateral bu...

Arabidopsis contains 20 MAP kinase genes, but their roles in plant physiology have remained largely unknown because of a lack of mutants. Recent papers from two groups have shed new light on the function of two different MAP kinases. The Arabidopsis MPK4 gene appears to negatively regulate salicylic acid-mediated defense responses and positively regulate jasmonic acid-induced responses. The tob...

The lipoxygenase pathway is responsible for the production of oxylipins, which are important compounds for plant defence responses. Jasmonic acid, the final product of the allene oxide synthase/allene oxide cyclase branch of the pathway, regulates wound-induced gene expression. In contrast, C6 aliphatic aldehydes produced via an alternative branch catalysed by hydroperoxide lyase, are themselve...

Two cDNA clones for jasmonic acid (JA)-responsive genes, RRJ1 and RRJ2, were isolated by differential screening from suspension-cultured rice cells treated with JA for 2 h. The putative RRJ1 protein is completely identical to that of a putative rice cystathionine gamma-lyase, while the putative RRJ2 protein is highly similar in sequence to a rice pyruvate decarboxylase, PDC1.

Allene oxide synthase (AOS) is a cytochrome P-450 (CYP74A) that catalyzes the first step in the conversion of 13-hydroperoxy linolenic acid to jasmonic acid and related signaling molecules in plants. Here, we report the molecular cloning and characterization of a novel AOS-encoding cDNA (LeAOS3) from Lycopersicon esculentum whose predicted amino acid sequence classifies it as a member of the CY...

Jasmonates are oxylipin signals that play important roles in the development of fertile flowers and in defense against pathogens and herbivores in leaves. The aim of this work was to understand the synthesis and function of jasmonates in roots. Grafting experiments with a jasmonate-deficient mutant demonstrated that roots produce jasmonates independently of leaves, despite low expression of bio...