Leaf-size control beyond transcription factors: Compensatory mechanisms

Abstract

Plant leaves display abundant morphological richness yet grow to characteristic sizes and shapes. Beginning with a small number of undifferentiated founder cells, leaves evolve via a complex interplay of regulatory factors that ultimately influence cell proliferation and subsequent post-mitotic cell enlargement. During their development, a sequence of key events that shape leaves is both robustly executed spatiotemporally following a genomic molecular network and flexibly tuned by a variety of environmental stimuli. Decades of work on Arabidopsis thaliana have revisited the compensatory phenomena that might reflect a general and primary size-regulatory mechanism in leaves. This review focuses on key molecular and cellular events behind the organ-wide scale regulation of compensatory mechanisms. Lastly, emerging novel mechanisms of metabolic and hormonal regulation are discussed, based on recent advances in the field that have provided insights into, among other phenomena, leaf-size regulation.

Leaf growth – complex regulation of a seemingly simple process

“…An extreme case is the er allele, which displays an almost halved epidermal cell area phenotype, which is largely compensated by an almost doubled cell number, not showing any significant difference in final leaf size (Tisné et al., 2011). However, studying compensation in determinate organs such as leaves or petals is complicated as it is achievable via different means or a combination thereof rather than a singular mechanism (Ferjani et al., 2007; Randall, Sornay, et al., 2015; Tabeta et al., 2022). These mechanisms include, for example, an altered cell expansion rate or cell expansion duration and can be regulated in cell‐autonomous and cell‐non‐autonomous manners (Ferjani et al., 2007; Kawade et al., 2010).…”

Sepal shape variability is robust to cell size heterogeneity in Arabidopsis

“…There are examples where increasing cell size also increases organ shape, and others where increase in cell size is compensated (e.g. by decreasing cell number) [2,3]. In either case, how this affects the standard deviation in organ shape (a proxy for organ shape robustness) is ill-documented.…”

Sepal shape variability is robust to cell size heterogeneity in Arabidopsis

“…There are examples where increasing cell size also increases organ shape, and others where the increase in cell size is compensated (e.g. by decreasing cell number) [2,3]. In either case, how this affects the standard deviation in organ shape (a proxy for organ shape robustness) is ill-documented.…”