RT Journal Article SR Electronic T1 Arabidopsis Leaf Flatness Is Regulated by PPD2 and NINJA through Repression of CYCLIN D3 Genes JF Plant Physiology JO Plant Physiol. FD American Society of Plant Biologists SP 217 OP 232 DO 10.1104/pp.18.00327 VO 178 IS 1 A1 Baekelandt, Alexandra A1 Pauwels, Laurens A1 Wang, Zhibiao A1 Li, Na A1 De Milde, Liesbeth A1 Natran, Annelore A1 Vermeersch, Mattias A1 Li, Yunhai A1 Goossens, Alain A1 Inzé, Dirk A1 Gonzalez, Nathalie YR 2018 UL http://www.plantphysiol.org/content/178/1/217.abstract AB In Arabidopsis (Arabidopsis thaliana), reduced expression of the transcriptional regulator PEAPOD2 (PPD2) results in propeller-like rosettes with enlarged and dome-shaped leaves. However, the molecular and cellular processes underlying this peculiar phenotype remain elusive. Here, we studied the interaction between PPD2 and NOVEL INTERACTOR OF JAZ (NINJA) and demonstrated that ninja loss-of-function plants produce rosettes with dome-shaped leaves similar to those of ppd mutants but without the increase in size. We showed that ninja mutants have a convex-shaped primary cell cycle arrest front, putatively leading to excessive cell division in the central leaf blade region. Furthermore, ppd and ninja mutants have a similar increase in the expression of CYCLIN D3;2 (CYCD3;2), and ectopic overexpression of CYCD3;2 phenocopies the ppd and ninja rosette and leaf shape phenotypes without affecting the size. Our results reveal a pivotal contribution of NINJA in leaf development, in addition to its well-studied function in jasmonate signaling, and imply a new function for D3-type cyclins in, at least partially, uncoupling the size and shape phenotypes of ppd leaves.