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Inger Holme

Heterologous microProtein expression identifies LITTLE NINJA, a dominant regulator of jasmonic acid signaling

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  • Shin-Young Hong, University of Copenhagen, Denmark
  • Bin Sun, University of Copenhagen, Denmark
  • Daniel Straub, University of Copenhagen, Denmark
  • Anko Blaakmeer, University of Copenhagen, Denmark
  • Lorenzo Mineri, University of Copenhagen, Department of Agricultural and Environmental Sciences, University of Milan, 20133 Milan, Italy, Denmark
  • Jonas Koch, University of Copenhagen, Denmark
  • Henrik Brinch-Pedersen
  • Inger B Holme
  • Meike Burow, University of Copenhagen, Denmark
  • Hans Jørgen Lyngs Jørgensen, University of Copenhagen, Denmark
  • M Mar Albà, Evolutionary Genomics Group, Research Programme on Biomedical Informatics, Hospital del Mar Research Institute, Universitat Pompeu Fabra, 08003 Barcelona, Spain, Catalan Institution for Research and Advanced Studies, 08003 Barcelona, Spain, Spain
  • Stephan Wenkel, University of Copenhagen

MicroProteins are small, often single-domain proteins that are sequence-related to larger, often multidomain proteins. Here, we used a combination of comparative genomics and heterologous synthetic misexpression to isolate functional cereal microProtein regulators. Our approach identified LITTLE NINJA (LNJ), a microProtein that acts as a modulator of jasmonic acid (JA) signaling. Ectopic expression of LNJ in Arabidopsis resulted in stunted plants that resembled the decuple JAZ (jazD) mutant. In fact, comparing the transcriptomes of transgenic LNJ overexpressor plants and jazD revealed a large overlap of deregulated genes, suggesting that ectopic LNJ expression altered JA signaling. Transgenic Brachypodium plants with elevated LNJ expression levels showed deregulation of JA signaling as well and displayed reduced growth and enhanced production of side shoots (tiller). This tillering effect was transferable between grass species, and overexpression of LNJ in barley and rice caused similar traits. We used a clustered regularly interspaced short palindromic repeats (CRISPR) approach and created a LNJ-like protein in Arabidopsis by deleting parts of the coding sentence of the AFP2 gene that encodes a NINJA-domain protein. These afp2-crispr mutants were also stunted in size and resembled jazD Thus, similar genome-engineering approaches can be exploited as a future tool to create LNJ proteins and produce cereals with altered architectures.

Original languageEnglish
JournalProceedings of the National Academy of Sciences of the United States of America
Pages (from-to)26197-26205
Number of pages9
Publication statusPublished - Oct 2020

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