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 ofLNJinArabidopsisresulted in stunted plants that resembled the decupleJAZ(jazD) mutant. In fact, comparing the transcriptomes of transgenicLNJoverexpressor plants andjazDrevealed a large overlap of deregulated genes, suggesting that ectopicLNJexpression altered JA signaling. Transgenic Brachypodium plants with elevatedLNJexpression 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 ofLNJin barley and rice caused similar traits. We used a clustered regularly interspaced short palindromic repeats (CRISPR) approach and created a LNJ-like protein inArabidopsisby deleting parts of the coding sentence of theAFP2gene that encodes a NINJA-domain protein. Theseafp2-crisprmutants were also stunted in size and resembledjazD. Thus, similar genome-engineering approaches can be exploited as a future tool to create LNJ proteins and produce cereals with altered architectures.
Argonaute4 Modulates Resistance to Fusariumbrachygibbosum Infection by Regulating Jasmonic Acid Signaling
