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Title: Molecular regulation of plant developmental transitions and plant architecture via PEPB family proteins – an update on mechanism of action
Abstract This year marks the 100 th anniversary of the experiments by Garner and Allard (Garner and Allard, 1920) that showed that plants measure the duration of the night and day (the photoperiod) to time flowering. This discovery led to the identification of Flowering Locus T (FT) in Arabidopsis and Heading Date 3a (Hd3a) in rice as a mobile signal that promotes flowering in tissues distal to the site of cue perception. FT/Hd3a belong to the family of phosphatidylethanolamine binding proteins (PEBPs). Collectively, these proteins control plant developmental transitions and plant architecture. Several excellent recent reviews have focused on the roles of PEBP proteins in diverse plant species; here we will primarily highlight recent advances that enhance our understanding of the mechanism of action of PEBP proteins and discuss critical open questions.  more » « less
Award ID(s):
1905062
NSF-PAR ID:
10211880
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Journal of Experimental Botany
ISSN:
0022-0957
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. We assessed mechanistic temperature influence on flowering by incorporating temperature-responsive flowering mechanisms across developmental age into an existing model. Temperature influences the leaf production rate as well as expression of FLOWERING LOCUS T (FT), a photoperiodic flowering regulator that is expressed in leaves. The Arabidopsis Framework Model incorporated temperature influence on leaf growth but ignored the consequences of leaf growth on and direct temperature influence of FT expression. We measured FT production in differently aged leaves and modified the model, adding mechanistic temperature influence on FT transcription, and causing whole-plant FT to accumulate with leaf growth. Our simulations suggest that in long days, the developmental stage (leaf number) at which the reproductive transition occurs is influenced by day length and temperature through FT, while temperature influences the rate of leaf production and the time (in days) the transition occurs. Further, we demonstrate that FT is mainly produced in the first 10 leaves in the Columbia (Col-0) accession, and that FT accumulation alone cannot explain flowering in conditions in which flowering is delayed. Our simulations supported our hypotheses that: (i) temperature regulation of FT, accumulated with leaf growth, is a component of thermal time, and (ii) incorporating mechanistic temperature regulation of FT can improve model predictions when temperatures change over time. 
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  2. Summary

    LIKE HETEROCHROMATIN PROTEIN1 (LHP1) encodes the only plant homologue of the metazoan HETEROCHROMATIN PROTEIN1 (HP1) protein family. The LHP1 protein is necessary for proper epigenetic regulation of a range of developmental processes in plants. LHP1 is a transcriptional repressor of flowering‐related genes, such asFLOWERING LOCUS T(FT),FLOWERING LOCUS C(FLC),AGAMOUS(AG) andAPETALA 3(AP3). We found that LHP1 interacts with importin α‐1 (IMPα‐1), importin α‐2 (IMPα‐2) and importin α‐3 (IMPα‐3) bothin vitroandin vivo. A genetic approach revealed that triple mutation ofimpα‐1,impα‐2andimpα‐3resulted in Arabidopsis plants with a rapid flowering phenotype similar to that of plants with mutations inlhp1due to the upregulation ofFTexpression. Nuclear targeting of LHP1 was severely impaired in theimpαtriple mutant, resulting in the de‐repression of LHP1 target genesAG,AP3andSHATTERPROOF 1as well asFT. Therefore, the importin proteins IMPα‐1, ‐2 and ‐3 are necessary for the nuclear import of LHP1.

     
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  3. Abstract Background

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    Results

    We studied molecular features of the FT homologs in prokaryotes and analyzed their genome context, to find tentative evidence connecting the bacterial FT homologs with small molecule metabolism, often involving substrates that contain sugar or ribonucleoside moieties. We argue that the unifying feature of this protein family, i.e., a set of charged residues conserved at the sequence and structural levels, is more likely to be an enzymatic active center than a catalytically inert ligand-binding site.

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    We propose that most of FT-related proteins are enzymes operating on small diffusible molecules. Those metabolites may constitute an overlooked essential ingredient of the florigen signal.

     
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  5. Abstract

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