Abstract
In response to cold, E. coli accumulates cold shock proteins (CSPs) that function as RNA chaperones. Plant cold shock domain (CSD) proteins contain a CSD that is highly conserved with bacterial CSPs. Wheat and Arabidopsis CSD proteins have been characterized and shown to have an RNA chaperone activity in our previous studies. Here, we performed functional characterization of AtCSP2, one of the four Arabidopsis CSPs (AtCSP1-4). AtCSP2 overexpression plants showed delayed germination, smaller plant size, late flowering and were less freezing tolerant than wild-type after cold acclimation. A T-DNA mutant with decreased AtCSP2 expression exhibited no perceptible phenotype on plant growth and freezing tolerance. The mutant was crossed with a knock-out mutant of AtCSP4 which shows the highest homology to AtCSP2, and the resulting double mutant showed early flowering and increased freezing tolerance after cold acclimation. Real-time PCR analysis of the double mutant revealed up-regulation of CBF transcription factors and their downstream genes. These data suggested that AtCSP2 regulates induced freezing tolerance during cold acclimation in Arabidopsis.
