The E3 Ubiquitin Ligase HOS1 Regulates Low Ambient Temperature-Responsive Flowering in Arabidopsis thaliana

Sep 11, 2012Plant & cell physiology

The protein HOS1 controls how Arabidopsis plants flower in response to cold temperatures

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

HOS1, an E3 ubiquitin ligase, regulates flowering time in response to ambient temperatures of 16 and 23°C.

hos1 mutants flowered early and were insensitive to ambient temperature changes.
The early flowering in hos1 mutants was independent of the FLOWERING LOCUS C (FLC).
Expression levels of FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF) increased in hos1 mutants at both temperatures.
The ft tsf mutation significantly suppressed the early flowering of hos1 mutants across different temperatures.
HOS1 co-localized with FVE in the nucleus and physically interacted with FVE and FLK.
hos1 mutants did not respond to intermittent cold conditions.

AI simplified

Ubiquitin-dependent proteolysis regulates multiple aspects of plant growth and development, but little is known about its role in ambient temperature-responsive flowering. In addition to being regulated by daylength, the onset of flowering in many plants can also be delayed by low ambient temperatures. Here, we show that HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1 (HOS1), which encodes an E3 ubiquitin ligase, controls flowering time in response to ambient temperatures (16 and 23°C) and intermittent cold. hos1 mutants flowered early, and were insensitive to ambient temperature, but responded normally to vernalization and gibberellic acid. Genetic analyses suggested that this ambient temperature-insensitive flowering was independent of FLOWERING LOCUS C (FLC). Also, FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF) expression was up-regulated in hos1 mutants at both temperatures. The ft tsf mutation almost completely suppressed the early flowering of hos1 mutants at different temperatures, suggesting that FT and TSF are downstream of HOS1 in the ambient temperature response. A lesion in CONSTANS (CO) did not affect the ambient temperature-insensitive flowering phenotype of hos1-3 mutants. In silico analysis showed that FVE was spatiotemporally co-expressed with HOS1. A HOS1-green fluorescent protein (GFP) fusion co-localized with FVE-GFP in the nucleus at both 16 and 23°C. HOS1 physically interacted with FVE and FLK in yeast two-hybrid and co-immunoprecipitation assays. Moreover, hos1 mutants were insensitive to intermittent cold. Collectively, our results suggest that HOS1 acts as a common regulator in the signaling pathways that control flowering time in response to low ambient temperature.

Full Text

Full text is available at the source.

View full text ↗

The E3 Ubiquitin Ligase HOS1 Regulates Low Ambient Temperature-Responsive Flowering in Arabidopsis thaliana

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief