Editors' ChoicePlant biology

Defense Without Compromising Development

Science Signaling  04 Jun 2013:
Vol. 6, Issue 278, pp. ec129
DOI: 10.1126/scisignal.2004394

Jasmonate is a plant phytohormone that functions in pathogen resistance and in developmental signaling. So far, all of the jasmonate-responsive proteins function in both processes (see Zhu and Zhu), compromising the ability to target this pathway to improve plant pathogen resistance. Hu et al. performed an RNAi (RNA interference) screen in Arabidopsis thaliana to identify genes that when knocked down increased plant resistance to the fungus Botrytis cinerea without altered development and identified the gene At3g22160, which encoded a protein of unknown function with a VQ motif and which the authors named JAV1 (jasmonate-associated VQ motif gene 1). Sequence comparisons indicated that this was a plant-specific gene because homologs were not found in animals or prokaryotes. Analysis of JAV1-targeted RNAi knockdown plant lines showed that the plants exhibited enhanced resistance to not only B. cinera but also insect attack by Spodoptera exigua and aphids. Indeed, the JAV1-knockdown plants exhibited reduced consumption by S. exigua, and the larvae were smaller. Aphids preferred to infect wild-type plants or plants deficient in the E3 ligase adaptor COI1, which is necessary for jasmonate-mediated activation of plant defense signals. When forced to grow on the JAV1-knockdown plants, aphids showed inhibited development. Transcriptional profiling and selected mRNA analysis showed that JAV1-knockdown plants had enhanced expression of plant defense genes in response to jasmonate or wounding. Similar to the JAZ transcriptional repressors that are degraded by the COI1-containing E3 ligase complex in a jasmonate-dependent manner, JAV1 was also degraded in a COI1-dependent manner. However, unlike the JAZ proteins, JAV1 did not directly interact with COI1 or JAZ1, suggesting that the mechanism for jasmonate-mediated degradation of JAV1 involves additional proteins. Although there are clearly gaps in the pathway from jasmonate to JAV1, the identification of this defense-specific regulator suggests that it may be possible to selectively manipulate this jasmonate pathway.

P. Hu, W. Zhou, Z. Cheng, M. Fan, L. Wang, D. Xie, JAV1 controls jasmonate-regulated plant defense. Mol. Cell 50, 504–515 (2013). [PubMed]

X. Zhu, J.-K. Zhu, Double repression in jasmonate-mediated plant defense. Mol. Cell 50, 459–460 (2013). [PubMed]

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