Monocot-specificmiR528act as the post-transcriptional regulator of strigolactone signaling viaDwarf 3in rice

Summary miRNAs are a critical component of regulatory mechanisms involved in plant growth, development, and stress response including phytohormone action. The role of miRNAs in regulating the strigolactone (SL) signaling in plants is still unexplored. Here we report that miR528 impacts the SL signaling via the post-transcriptional regulation of Dwarf 3 ( OsD3 ). Comparative miRNome analysis under drought conditions in flag leaf, inflorescence, and roots uncovered the tissue-biased unique stress response of miR528 in drought-tolerant N22 (down in inflorescence and roots; up in flag leaf). Consequently, its target, OsD3 which encodes for the F-BOX/LRR-REPEAT MAX2 HOMOLOG and is a critical component of the rice SL signaling pathway exhibit opposite expression to miR528 in all three tissues. Interestingly, OsD3 is a rice-specific target of miR528. miR528 overexpression plants exhibited early heading, increment in the number of tillers, flag leaf length, and width, number of panicle branches, grain per panicle, effective grains per panicle, seed length, and photosynthesis rate. miR528 overexpression plants exhibited similar traits to Osd3 mutants including high tiller number, root architecture under low nitrogen conditions, and moderate insensitivity to GR24 and TIS1 levels in addition to shared transcriptional regulation. Furthermore, SL (GR24) negatively impacts the miR528 transcription. The impact of the miR528:D3 module is also reflected in the D53-mediated downstream signaling involving IPA1 regulon.