Robust organ size requires robust timing of initiation orchestrated by focused auxin and cytokinin signalling

Abstract

Organ size and shape are precisely regulated to ensure proper function. The four sepals in each Arabidopsis thaliana flower must maintain the same size throughout their growth to enclose and protect the developing bud. Here we show that DEVELOPMENT RELATED MYB-LIKE1 (DRMY1) is required for both timing of organ initiation and proper growth, leading to robust sepal size in Arabidopsis. Within each drmy1 flower, the initiation of some sepals is variably delayed. Late-initiating sepals in drmy1 mutants remain smaller throughout development resulting in variability in sepal size. DRMY1 focuses the spatiotemporal signaling patterns of the plant hormones auxin and cytokinin, which jointly control the timing of sepal initiation. Our findings demonstrate that timing of organ initiation together with growth and maturation contribute to robust organ size.

Stable establishment of organ polarity occurs several plastochrons before primordium outgrowth in Arabidopsis

“…Soon after the inactivation of pDRNL and pFIL in the cryptic bract, the sepal primordia are specified. This is marked by a local activation of pDRNL , first in the outer (abaxial) primordium and two lateral primordia ( Zhu et al, 2020 ). At late stage 2, pDRNL is activated in all four sepal primordia.…”

“…Several genes have been associated with leaf shape and size, which are determined from the earliest stages of development onwards (e.g. Hervieux et al, 2016 ; Zhao et al, 2020 ; Zhu et al, 2020 ). Key are the regulators involved in establishing leaf polarity and which are activated before or during organ outgrowth.…”

Auxin and Flower Development: A Blossoming Field

“…The concentration of free auxin, indicated by DR5::GUS, is high in the tips of floral organ primordia in all whorls (Aloni et al 2006), which drives rapid organ outgrowth. After the specification of sepal founder cells in a stereotypic order (Chandler and Werr 2014), sepal outgrowth in Arabidopsis is coordinated by DEVEL-OPMENT-RELATED MYB-LIKE1 (DRMY1) (Zhu et al 2020). Coordinated auxin and cytokinin signaling regulates sepal outgrowth, analogous to the temporal regulation of FM outgrowth (Besnard et al 2014).…”

Biosensors: A Sneak Peek into Plant Cell’s Immunity

“…The dual GECO sensor was shown to be a useful tool to monitor Ca 2+ signal response to biotic and abiotic stress of Medicago truncatula and A. thaliana roots [ 28 ]. Another example of dual sensors is the use of transgenic A. thaliana plants simultaneously expressing DR5::3xVENUS-N7 [ 77 ] and TCS::GFP [ 57 ] reporters to study the spatial patterns of auxin and cytokinins, respectively [ 78 ].…”