Alternative splicing and expression analysis of High expression of osmotically responsive genes1 (HOS1) in Arabidopsis

High expression of osmotically responsive genes1 (HOS1), akey regulator of low temperature response and flowering time,encodes an E3 ubiquitin ligase in Arabidopsis. Here, we reportcharacterization of a newly identified splice variant (HOS1-L)of HOS1. Comparative analyses revealed that HOS1-L has alonger 5' nucleotide sequence than that of the previouslyidentified HOS1 (HOS1-S) and that its protein sequence wasmore conserved than that of HOS1-S in plants. HOS1-Ltranscripts were spatio-temporally more abundant than thoseof HOS1-S. The recovery rate of HOS1-S expression was fasterthan that of HOS1-L after cold treatment. Diurnal oscillationpatterns of HOS1-L revealed that HOS1-L expression wasaffected by photoperiod. An in vitro pull-down assay revealedthat the HOS1-L protein interacted with the ICE1 protein.HOS1-L overexpression caused delayed flowering in wild-typeplants. Collectively, these results suggest regulation of HOS1expression at the post-transcriptional level.