Populus SVL Acts in Leaves to Modulate the Timing of Growth Cessation and Bud Set.

Domenique André,José Alfredo Zambrano,Alice Marcon,Ove Nilsson,Keh Chien Lee,Bo Zhang,Mark Rühl

doi:10.3389/fpls.2022.823019

Domenique André, José Alfredo Zambrano + Show 5 more

Open Access

https://doi.org/10.3389/fpls.2022.823019

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Abstract

SHORT VEGETATIVE PHASE (SVP) is an important regulator of FLOWERING LOCUS T (FT) in the thermosensory pathway of Arabidopsis. It is a negative regulator of flowering and represses FT transcription. In poplar trees, FT2 is central for the photoperiodic control of growth cessation, which also requires the decrease of bioactive gibberellins (GAs). In angiosperm trees, genes similar to SVP, sometimes named DORMANCY-ASSOCIATED MADS-BOX genes, control temperature-mediated bud dormancy. Here we show that SVL, an SVP ortholog in aspen trees, besides its role in controlling dormancy through its expression in buds, is also contributing to the regulation of short day induced growth cessation and bud set through its expression in leaves. SVL is upregulated during short days in leaves and binds to the FT2 promoter to repress its transcription. It furthermore decreases the amount of active GAs, whose downregulation is essential for growth cessation, by repressing the transcription of GA20 oxidase. Finally, the SVL protein is more stable in colder temperatures, thus integrating the temperature signal into the response. We conclude that the molecular function of SVL in the photoperiodic pathway has been conserved between Arabidopsis and poplar trees, albeit the physiological process it controls has changed. SVL is thus both involved in regulating the photoperiod response in leaves, modulating the timing of growth cessation and bud set, and in the subsequent temperature regulation of dormancy in the buds.

Highlights

Photoperiod is an important environmental cue that controls diverse developmental processes in plants, for example, flowering in Arabidopsis and timing of growth cessation in Populus trees (Pin and Nilsson, 2012)
Because of the high similarity to SHORT VEGETATIVE PHASE (SVP) (Supplementary Figure S1B), we hypothesized that SVL could act like SVP in Arabidopsis by having a function in the photoperiodic response in leaves
The svp mutant is early flowering (Hartmann et al, 2000) and we tested whether SVL could rescue this phenotype

Summary

Introduction

Photoperiod is an important environmental cue that controls diverse developmental processes in plants, for example, flowering in Arabidopsis and timing of growth cessation in Populus trees (Pin and Nilsson, 2012). At the center of the mechanism, with which plants sense day length, is the CONSTANS/FLOWERING LOCUS T module. This module is partially conserved between Populus and Arabidopsis, but best understood in the latter. In Arabidopsis, FT expression is tightly regulated by many factors and becomes a hub for the integration of different signals, which fine-tunes the response. In addition to photoperiod (Kobayashi et al, 1999), it is regulated by age (Wang, 2014), vernalization (Searle et al, 2006), and ambient temperature (Lee et al, 2007). SHORT VEGETATIVE PHASE (SVP) is part of the latter pathway and represses FT

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