Getting leaves into shape: a molecular, cellular, environmental and evolutionary view

Abstract

Leaves arise from groups of undifferentiated cells as small primordia that go through overlapping phases of morphogenesis, growth and differentiation. These phases are genetically controlled and modulated by environmental cues to generate a stereotyped, yet plastic, mature organ. Over the past couple of decades, studies have revealed that hormonal signals, transcription factors and miRNAs play major roles during leaf development, and more recent findings have highlighted the contribution of mechanical signals to leaf growth. In this Review, we discuss how modulating the activity of some of these regulators can generate diverse leaf shapes during development, in response to a varying environment, or between species during evolution.

Karyological and molecular analysis of Leucanthemum (Compositae, Anthemideae) in Corsica

“…On the other hand, and in support of the adaptation argument, it has also been demonstrated that leaf-blade dissection may be under oligogenic control (Sicard & al. 2014;Maugarny-Calès & Laufs 2018). This may explain our present observation that variation in ecologically adaptive and taxonomically decisive morphological features is not paralleled by genetic patterns based on molecular markers scattered throughout the whole genome like AFLP fingerprint loci.…”

Autoregulation of RCO by Low-Affinity Binding Modulates Cytokinin Action and Shapes Leaf Diversity

“…Plant leaves provide a powerful model in which to explore such questions on the mechanistic basis of evolutionary change because they show substantial, heritable morphological variation at different evolutionary scales and are ecophysiologically important because they fix CO 2 in terrestrial ecosystems [16,17]. Considerable insights into the genetic basis for diversification of leaf shape have come from comparative studies of simple leaves of the reference plant A. thaliana versus complex leaves of its relative Cardamine hirsuta, where leaves are divided into distinct units called leaflets.…”

The Times They Are A-Changin’: Heterochrony in Plant Development and Evolution

“…This shift correlates with the role of sugar in promoting the Target of Rapamycin (TOR) pathway and repressing the Sucrose-non-fermenting1-related kinase 1 (SnRK1): TOR and T6P induce cell expansion by promoting macromolecular synthesis, whereas SnRK1 promotes catabolism ( Tsai and Gazzarrini, 2014 ; Sablowski, 2016 ). Two microRNAs play opposite roles in this cellular shift: miR319 represses the expression of class II TCP factors, which are inhibitors of cell proliferation, whereas miR396 restricts the expression of GROWTH REGULATING FACTORS (GRFs), which delay differentiation ( Das Gupta and Nath, 2015 ; Maugarny-Calés and Laufs, 2018 ). The transition from an indeterminate shoot apical meristem to a determinate floral meristem also involves temporal regulation of the cellular identity.…”