DNA Topoisomerase Iα Affects the Floral Transition

Abstract

ORCID ID: 0000-0002-9778-8855 (H.Y.).DNA topoisomerases modulate DNA topology to maintain chromosome superstructure and genome integrity, which is indispensable for DNA replication and RNA transcription. Their function in plant development still remains largely unknown. Here, we report a hitherto unidentified role of Topoisomerase Ia (TOP1a) in controlling flowering time in Arabidopsis (Arabidopsis thaliana). Loss of function of TOP1a results in early flowering under both long and short days. This is attributed mainly to a decrease in the expression of a central flowering repressor, FLOWERING LOCUS C (FLC), and its close homologs, MADS AFFECTING FLOWERING4 (MAF4) and MAF5, during the floral transition. TOP1a physically binds to the genomic regions of FLC, MAF4, and MAF5 and promotes the association of RNA polymerase II complexes to their transcriptional start sites. These correlate with the changes in histone modifications but do not directly affect nucleosome occupancy at these loci. Our results suggest that TOP1a mediates DNA topology to facilitate the recruitment of RNA polymerase II at FLC, MAF4, and MAF5 in conjunction with histone modifications, thus facilitating the expression of these key flowering repressors to prevent precocious flowering in Arabidopsis.

Abscisic Acid and Gibberellins Antagonistically Mediate Plant Development and Abiotic Stress Responses

“…During the plant life cycle, the appropriate flowering time is a crucial and important checkpoint for growth and survival, especially under diverse environmental stress conditions. The positive effect of GA on plant floral transition has been extensively and intensively explored and documented ( Ding et al, 2013 ; Hyun et al, 2016 ; Zhu et al, 2016 ; Brambilla et al, 2017 ; Conti, 2017 ; Gong et al, 2017 ; Sawettalake et al, 2017 ).…”

TOP1α regulates FLOWERING LOCUS C expression by coupling histone modification and transcription machinery

“…Our data indicate that the recruitment of histone modifications to regulate transcription might be a unique feature of plant type IB topoisomerases. Interestingly, in plants, TOP1α is also required for silencing Polycomb group (PcG) target genes by increasing the repressive mark of H3K27me3 at the promoter region (Liu et al, 2014), or transposable elements by RNAPV-dependent RNA-directed DNA methylation (RdDM) and H3K9me2 (Dinh et al, 2014). Therefore, it remains to be determined whether TOP1α directly recruits a variety of histone methyltransferases and different types of RNA polymerases to either positively or negatively regulate gene expression at different transcriptional stages, and how these activities are specified during plant development.…”

TOP1α, UPF1, and TTG2 regulate seed size in a parental dosage–dependent manner

“…Interestingly, TOP1α not only affects flowering time [16] but also influences seed size (Fig 1A and 1B and S1A Fig). To identify interacting partners of TOP1α, we performed co-immunoprecipitation (CoIP) coupled with liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) using nuclear extracts of young siliques from the established top1α-10 gTOP1α-4HA line [16]. A peptide corresponding to UPF1 was identified, and the Abbreviations: 3C, chromatin conformation capture; BiFC, bimolecular fluorescence complementation; ChIP, chromatin immunoprecipitation; CoIP, coimmunoprecipitation; CPT, camptothecin; DAP, days after pollination; DRIP, DNA:RNA hybrid immunoprecipitation; FAIRE, formaldehydeassisted isolation of regulatory elements; GUS, βglucuronidase; iku1, haiku1; LC-MS/MS, liquid chromatography coupled with tandem mass spectrometry; mCIP, methyl-cytosine immunoprecipitation; MEG, maternally expressed gene; mini3, miniseed3; NLS, nuclear localization signal; NMD, non-sense mRNA decay; PEG, paternally expressed gene; qPCR, quantitative PCR; SHB1, SHORT HYPOCOTYL UNDER BLUE1; SSP, SHORT SUSPENSOR; TOP1α, TOPOISOMERASE Iα; TTG2, TRANSPARENT TESTA GLABRA2; UPF1, UP-FRAMESHIFT SUPPRESSOR 1; Wa-1, Warschau.…”

“…The top1α-10 gTOP1α-4HA was validated in the previous study [16]. upf1-1 top1α-10 gTOP1α-4HA was generated by genetic crossing.…”

“…In Arabidopsis, TOP1α (AT5G55300) is the major type I topoisomerase [15]. Interestingly, TOP1α not only affects flowering time [16] but also influences seed size (Fig 1A and 1B and S1A Fig). To identify interacting partners of TOP1α, we performed co-immunoprecipitation (CoIP) coupled with liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) using nuclear extracts of young siliques from the established top1α-10 gTOP1α-4HA line [16].…”