SIZ1, a small ubiquitin-related modifier ligase, controls cold signaling through regulation of salicylic acid accumulation

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Low temperature induces several genes to acquire plant cold tolerance. Here, we demonstrate that accumulation of salicylic acid (SA) is involved in the regulation of the DREB1A/CBF3 regulon and plant tolerance to cold stresses. The SA-accumulating mutant siz1 exhibits sensitivity to chilling and freezing conditions and decreased expression of DREB1A/CBF3 and its regulon genes. Reduction of SA levels in siz1 by nahG restored cold sensitivity and down-regulation of these genes. Database analyses and RT-PCR analysis revealed that the ice1 mutation also increased expression of SA-responsive genes. As well as siz1, another SA-accumulating mutant acd6 exhibited freezing sensitivity and the sensitivity was suppressed in acd6 nahG plants. Taken together, these data indicate that SA is involved in regulation of cold signaling.