Regulation of shoot meristem shape by photoperiodic signaling and phytohormones during floral induction of Arabidopsis

Abstract

Floral transition, the onset of plant reproduction, involves changes in shape and identity of the shoot apical meristem (SAM). The change in shape, termed doming, occurs early during floral transition when it is induced by environmental cues such as changes in day-length, but how it is regulated at the cellular level is unknown. We defined the morphological and cellular features of the SAM during floral transition of Arabidopsis thaliana. Both cell number and size increased during doming, and these changes were partially controlled by the gene regulatory network (GRN) that triggers flowering. Furthermore, dynamic modulation of expression of gibberellin (GA) biosynthesis and catabolism enzymes at the SAM contributed to doming. Expression of these enzymes was regulated by two MADS-domain transcription factors implicated in flowering. We provide a temporal and spatial framework for integrating the flowering GRN with cellular changes at the SAM and highlight the role of local regulation of GA.

Sugar Signaling Induces Dynamic Changes during Meristem Development to Regulate Flowering in Arabidopsis

“…To assess whether this is related to WUS or CLV3 expression in a wild-type SAM, we analyzed their expression in a time series spanning floral transition (Figure 1D). Throughout the vegetative phase SAM size gradually increases due to rising cell numbers (Figures 1A, S4) (Kinoshita et al ., 2020), reaching its maximum at floral transition, independent of whether the plants are grown in long days (LD) (Figure 1A) or in short days (SD) followed by a transfer to LD (Figure S5). An enlarging SAM at floral transition correlates with a larger WUS expression domain expanding into the CZ and the outer cell layer (L1) (Figure 1D-F).…”

“…1a; Fig. S4) 8 , reaching its maximum at the floral transition, independent of whether the plants are grown in continuous long days (LD) (Fig. 1a) or in short days (SD) followed by a transfer to LD (Fig.…”

“…Since this transition requires a massive reorganization of organ development and sufficient energy, it is tightly controlled by environmental conditions and availability of nutrients (Andres & Coupland, 2012; Olas et al , 2019; Ponnu et al , 2020; Srikanth & Schmid, 2011; Wahl et al , 2013). Only recently the early cellular changes were associated with floral regulators that control GA biosynthesis (Kinoshita et al , 2020). However, the knowledge on the mechanisms controlling doming is still scarce.…”

When vegetation indicates reproduction: The affinity between leaf morphology and flowering commitment in the lily meristem

“…The transition of a plant from the vegetative to the reproductive phase is a complicated process involving molecular, hormonal, physiological, and morphological changes (Conti, 2017; Kinoshita et al, 2020; Kinoshita & Richter, 2020). In some cases, juvenility is the first barrier to this switch, as the meristem is noncompetent and flowering signals cannot be perceived by the plant (Heide, 2018).…”

The role of FRUITFULL-like genes in the tomato flowering regulatory network

“…The role of GA in the regulation of the floral transition in Arabidopsis has been intensively studied. GA biosynthesis is repressed in the vegetative SAM, but upon the floral transition, GA promotes both cell division and expansion in the SAM epidermis to form the doming shape characteristic for the SAM (Kinoshita et al, 2020), a function that may be similar to that of CK in the tomato meristem (Chapters 3 and 4). Whether GA and CK share conserved functions in this process in both species needs to be further investigated.…”