Trifoliate encodes an MYB transcription factor that modulates leaf and shoot architecture in tomato

Abstract

Leaf morphology and the pattern of shoot branching determine to a large extent the growth habit of seed plants. Until recently, the developmental processes that led to the establishment of these morphological structures seemed unrelated. Here, we show that the tomato Trifoliate ( Tf ) gene plays a crucial role in both processes, affecting the formation of leaflets in the compound tomato leaf and the initiation of axillary meristems in the leaf axil. Tf encodes a myeloblastosis oncoprotein (MYB)-like transcription factor related to the Arabidopsis thaliana LATERAL ORGAN FUSION1 (LOF1) and LOF2 proteins. Tf is expressed in the leaf margin, where leaflets are formed, and in the leaf axil, where axillary meristems initiate. During tomato ontogeny, expression of Tf in young leaf primordia increases, correlating with a rise in leaf dissection (heteroblasty). Formation of leaflets and initiation of axillary meristems can be traced back to groups of pluripotent cells. Tf function is required to inhibit differentiation of these cells and thereby to maintain their morphogenetic competence, a fundamental process in plant development. KNOTTED1-LIKE proteins, which are known regulators in tomato leaf dissection, require Tf activity to exert their function in the basal part of the leaf. Similarly, the plant hormone auxin needs Tf activity to initiate the formation of lateral leaflets. Thus, leaf dissection and shoot branching rely on a conserved mechanism that regulates the morphogenetic competence of cells at the leaf margin and in the leaf axil.

Leaf development and morphogenesis

“…The TRIFOLIATE (TF) protein, which is a MYB transcription factor related to the A. thaliana LATERAL ORGAN FUSION1 (LOF1) protein, is required for the maintenance of morphogenetic potential during leaf development in tomato (Naz et al, 2013). tf mutants have simplified leaves that lack lobing and serrations.…”

CLAUSA is a MYB Transcription Factor that Promotes Leaf Differentiation by Attenuating Cytokinin Signaling

“…CLAU is a potential negative regulator of KNOXI genes and of the boundary gene GOBLET (GOB) (Bar et al, 2015;Avivi et al, 2000;Jasinski et al, 2007Jasinski et al, , 2008Naz et al, 2013).…”

Environmental Control of Branching in Petunia

“…In many species, these meristems are produced in every leaf axil soon after the boundary layer forms between the developing leaf primordium and the apical meristem (Bell et al, 2012;Gendron et al, 2012;Yang et al, 2012;Naz et al, 2013;Janssen et al, 2014). In a number of species, the growth of these meristems is suppressed based on their position on the plant.…”