title: Possible Role ofMADS AFFECTING FLOWERING 3andB-BOX DOMAIN PROTEIN 19in Flowering Time Regulation of Arabidopsis Mutants with Defects in Nonsense-Mediated mRNA Decay.
abstract: Eukaryotic cells use nonsense-mediated mRNA decay (NMD) to clear aberrant mRNAs from the cell, thus preventing the accumulation of truncated proteins. In Arabidopsis, two UP-Frameshift (UPF) proteins, UPF1 and UPF3, play a critical role in NMD. Although deficiency ofUPF1andUPF3leads to various developmental defects, little is known about the mechanism underlying the regulation of flowering time by NMD. Here, we showed that theupf1-5andupf3-1mutants had a late-flowering phenotype under long-day conditions and theupf1-5 upf3-1double mutants had an additive effect in delaying flowering time. RNA sequencing of theupfmutants revealed thatUPF3exerted a stronger effect thanUPF1in theUPF-mediated regulation of flowering time. Among genes known to regulate flowering time,FLOWERING LOCUS C(FLC) mRNA levels increased (up to 8-fold) inupfmutants, as confirmed by qPCR. Theupf1-5, upf3-1, andupf1-5 upf3-1mutants responded to vernalization, suggesting a role ofFLCin delayed flowering ofupfmutants. Consistent with the highFLCtranscript levels and delayed flowering inupfmutants, levels ofFLOWERING LOCUS T(FT) andSUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1(SOC1) mRNAs were reduced in theupfmutants. However, RNA-seq did not identify an aberrantFLCtranscript containing a premature termination codon (PTC), suggesting thatFLCis not a direct target in the regulation of flowering time by NMD. Among flowering time regulators that act in anFLC-dependent manner, we found thatMAF3, NF-YA2, NF-YA5, andTAF14showed increased transcript levels inupfmutants. We also found thatBBX19andATC, which act in anFLC-independent manner, showed increased transcript levels inupfmutants. An aberrant transcript containing a PTC was identified fromMAF3andBBX19and the levels of the aberrant transcripts increased inupfmutants. Taking these results together, we propose that the late-flowering phenotype ofupfmutants is mediated by at least two different pathways, namely, byMAF3in anFLC-dependent manner and byBBX19in anFLC-independent manner.
authors.affiliation: Creative Research Initiatives, Department of Life Sciences, Korea University Seoul, South Korea.
authors.forename: Zeeshan
authors.initials: Z
authors.lastname: Nasim
authors.affiliation: Genetic Resources Conservation Lab, Institute of Biotechnology and Genetic Engineering, University of Agriculture Peshawar, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Fahim
authors.affiliation: Creative Research Initiatives, Department of Life Sciences, Korea University Seoul, South Korea.
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Ahn
keywords: Arabidopsis; NMD; UPF1; UPF3; flowering