초록
<P>The <I>Arabidopsis</I> 14-3-3 RCI1A protein plays a critical role in freezing tolerance, partially through an ethylene-dependent signaling pathway. RCI1A interacts with different ACS isoforms to regulate the levels of ethylene that are necessary to promote accurate cold-induced gene expression and freezing tolerance under both control and low-temperature conditions.</P><P>In plants, the expression of 14-3-3 genes reacts to various adverse environmental conditions, including cold, high salt, and drought. Although these results suggest that 14-3-3 proteins have the potential to regulate plant responses to abiotic stresses, their role in such responses remains poorly understood. Previously, we showed that the <I>RARE COLD INDUCIBLE 1A</I> (<I>RCI1A</I>) gene encodes the 14-3-3 psi isoform. Here, we present genetic and molecular evidence implicating RCI1A in the response to low temperature. Our results demonstrate that RCI1A functions as a negative regulator of constitutive freezing tolerance and cold acclimation in <I>Arabidopsis thaliana</I> by controlling cold-induced gene expression. Interestingly, this control is partially performed through an ethylene (ET)-dependent pathway involving physical interaction with different ACC SYNTHASE (ACS) isoforms and a decreased ACS stability. We show that, consequently, RCI1A restrains ET biosynthesis, contributing to establish adequate levels of this hormone in <I>Arabidopsis</I> under both standard and low-temperature conditions. We further show that these levels are required to promote proper cold-induced gene expression and freezing tolerance before and after cold acclimation. All these data indicate that RCI1A connects the low-temperature response with ET biosynthesis to modulate constitutive freezing tolerance and cold acclimation in <I>Arabidopsis</I>.</P>