Elevated Levels of MYB30 in the Phloem Accelerate Flowering in Arabidopsis through the Regulation of FLOWERING LOCUS T

Liangyu Liu,Jessika Adrian,George Coupland,Jian Zhang,Franziska Turck,Diqiu Yu,Lionel Gissot,Hector Candela

doi:10.1371/journal.pone.0089799

Abstract

In Arabidopsis thaliana, the R2R3 MYB-like transcription factor MYB30 is a positive regulator of the pathogen-induced hypersensitive response and of brassinosteroid and abscisic acid signaling. Here, we show that MYB30 expressed under the control of the strong phloem-specific SUC2 promoter accelerates flowering both in long and short days. Early flowering is mediated by elevated expression of FLOWERING LOCUS T (FT), which can be observed in the absence and presence of CONSTANS (CO), the main activator of FT. CO-independent activation by high MYB30 expression results in FT levels that remain below those observed in the wild-type plants, which show an additive CO-dependent activation. In contrast, TWIN SISTER OF FT (TSF) is repressed in plants expressing high levels of MYB30 in the phloem. In transient assays, MYB30 and CO additively increase the activity of a reporter construct driven by a 1 kb FT promoter. Acceleration of flowering by MYB30 does not require the presence of salicylic acid and is independent of FLC. Taken together, increased levels of MYB30, which was reported to be induced in response to the perception of pathogens, can accelerate flowering and MYB30 may thus be a candidate to mediate cross-talk between gene networks involved in biotic stress perception and flowering time.

Highlights

Optimal timing of the transition from vegetative to reproductive development is a critical step for the successful reproduction of flowering plants
After the long distance movement, FLOWERING LOCUS T (FT) protein is unloaded to the shoot apical meristem cells, where it is proposed to migrate to the nuclei to form a complex with the bZIP transcription factor FLOWERING LOCUS D (FD) and 14-3-3 proteins [9,10,11]
Whether FT is a direct target of MYB30 or whether other factors mediate between the transcription factor and FT

Summary

Introduction

Optimal timing of the transition from vegetative to reproductive development is a critical step for the successful reproduction of flowering plants. In Arabidopsis, many regulatory inputs are channeled into the transcriptional regulation of FLOWERING LOCUS T (FT) [1,2]. FT encodes a major component of florigen, which transmits a flowering stimulus from the leaves to the apical meristem [3,4]. Arabidopsis plants carrying mutations in the FT locus flower late in long days (LD), but almost as wild-type plants if grown in short days (SD) [5]. After the long distance movement, FT protein is unloaded to the shoot apical meristem cells, where it is proposed to migrate to the nuclei to form a complex with the bZIP transcription factor FLOWERING LOCUS D (FD) and 14-3-3 proteins [9,10,11].

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Results

Conclusion