Identification of cotton MOTHER OF FT AND TFL1 homologs, GhMFT1 and GhMFT2, involved in seed germination.

Xiuli Yu,Yunfei Li,Na Sang,Jie Sun,Hui Liu,Tingting Zhang,Xianzhong Huang,Rosalyn B Angeles-Shim

doi:10.1371/journal.pone.0215771

Abstract

Plant phosphatidylethanolamine-binding protein (PEBP) is comprised of three clades: FLOWERING LOCUS T (FT), TERMINAL FLOWER1 (TFL1) and MOTHER OF FT AND TFL1 (MFT). FT/TFL1-like clades regulate identities of the determinate and indeterminate meristems, and ultimately affect flowering time and plant architecture. MFT is generally considered to be the ancestor of FT/TFL1, but its function is not well understood. Here, two MFT homoeologous gene pairs in Gossypium hirsutum, GhMFT1-A/D and GhMFT2-A/D, were identified by genome-wide identification of MFT-like genes. Detailed expression analysis revealed that GhMFT1 and GhMFT2 homoeologous genes were predominately expressed in ovules, and their expression increased remarkably during ovule development but decreased quickly during seed germination. Expressions of GhMFT1 and GhMFT2 homoeologous genes in germinating seeds were upregulated in response to abscisic acid (ABA), and their expressions also responded to gibberellin (GA). In addition, ectopic overexpression of GhMFT1 and GhMFT2 in Arabidopsis inhibited seed germination at the early stage. Gene transcription analysis showed that ABA metabolism genes ABA-INSENSITIVE3 (ABI3) and ABI5, GA signal transduction pathway genes REPRESSOR OF ga1-3 (RGA) and RGA-LIKE2 (RGL2) were all upregulated in the 35S:GhMFT1 and 35S:GhMFT2 transgenic Arabidopsis seeds. GhMFT1 and GhMFT2 localize in the cytoplasm and nucleus, and both interact with a cotton bZIP transcription factor GhFD, suggesting that both of GhMFT1, 2 have similar intracellular regulation mechanisms. Taken together, the results suggest that GhMFT1 and GhMFT2 may act redundantly and differentially in the regulation of seed germination.

Highlights

In the life cycle of higher plants, the transition from vegetative to reproductive growth is controlled by endogenous cues and external cues [1,2,3]
GhMFT1 open reading frame (ORF) is 519 bp encoding a protein of 172 aa; and GhMFT2 ORF is 528 bp encoding a protein of 175 aa (Panel A in S2 Fig)
The conserved key amino acid residues Tyr85 (Y)/His88 (H) in FLOWERING LOCUS T (FT)/ TERMINAL FLOWER1 (TFL1)-like protein are replaced by Trp83/85 (W) in GoMFT1 and GoMFT2, respectively, suggesting that GoMFT homologs do not play a central role in flowering time control

Summary

Introduction

In the life cycle of higher plants, the transition from vegetative to reproductive growth (floral transition) is controlled by endogenous cues and external cues [1,2,3]. Identification of cotton MOTHER OF FT AND TFL1 homologs, GhMFT1 and GhMFT2 molecular mechanisms of flowering initiation in Arabidopsis thaliana have uncovered six major pathways to orchestrate flowering time, such as photoperiod, vernalization, ambient temperature, gibberellin (GA), autonomous and age pathways [4]. Another transition in a flowering plant is from embryonic growth to germination growth [5]. DELLA proteins, consisting of REPRESSOR OF ga (RGA), GA-INSENSITIVE (GAI), and RGA-LIKE1-3 (RGL1-3) [20,21,22,23,24], act as repressors in regulating GA signaling, among which RGA and RGL2 play roles in inhibiting seed germination by mediating the interaction between GA and ABA [14, 22, 25]

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Discussion

Conclusion