Characterization of the low-temperature response of EARLI1 in Arabidopsis
Abstract
One approach toward understanding adaptation of plants to their environment is to investigate environmental regulation of gene expression. Our focus is on the environmental regulation of EARLI1 , which is activated by cold and long-day photoperiods. Cold activation of EARLI1 in short-day photoperiods is slow, requiring several hours at 4°C before an increase in mRNA abundance can be detected. EARLI1 is not efficiently cold-activated in etiolated seedlings, suggesting that photomorphogenesis is necessary for its cold activation. Cold activation of EARLI1 is inhibited in the presence of the calcium channel blocker lanthanum chloride or the calcium chelator EGTA. Addition of the calcium ionophore Bay K8644 results in cold-independent activation of EARLI1 . These data suggest that EARLI1 is not an immediate target of the cold response, and that calcium flux affects its expression. EARLI1 is a putative secreted protein and has motifs found in lipid transfer proteins. Overexpression of EARLI1 in transgenic plants has no effect upon flowering time but did result in reduced electrolyte leakage during freezing damage, suggesting that EARLI1 may affect membrane or cell wall stability in response to low temperature stress. In addition a cold acclimated transgenic line carrying an RNAi construct designed to knockout EARLI1 and possibly three of its family members, shows greater leakage than wild type-acclimated plants at -6 and -8°C. The regulation of EARLI1 was reconstituted using promoter::GUS fusions in transgenic plants to determine the minimal DNA fragment that responds to cold shock. A 100bp region between -1183 and -1085 appears to be sufficient to confer low-temperature induction upon a reporter gene, as assayed by northern hybridization. Within this region are two putative Myc and one Myb transcription factor binding sites.
This paper has been withdrawn.