LOS2, a genetic locus required for cold-responsive gene transcription encodes a bi-functional enolase

The Arabidopsis mutation, los2, impairs cold-responsive gene transcription, acquired freezing tolerance and plant resistance to chilling under certain conditions. LOS2 was isolated through positional cloning and shown to encode an enolase in the glycolytic pathway. In animal cells, enolase has also been known to function as a transcription factor that represses the expression of c-myc by binding to the c-myc gene promoter. LOS2 fused to green fluorescent protein is targeted to the nucleus as well as to the cytoplasm. LOS2/enolase protein can bind to the cis-element of the human c-myc gene promoter and to the gene promoter of STZ/ZAT10, a zinc finger transcriptional repressor from Arabidopsis. STZ/ZAT10 expression is induced rapidly and transiently by cold in the wild type, and this induction is stronger and more sustained in the los2 mutant. Furthermore, the expression of a RD29A-LUC reporter gene is repressed significantly by STZ/ZAT10 in transient expression assays in Arabidopsis leaves. Our results demonstrate that cold-responsive gene transcription in plants is controlled by a bi-functional enolase.

拟南芥（Arabidopsis）突变体los2可在特定条件下削弱植株的低温响应基因转录、获得性抗冻性以及耐冷性。研究人员通过图位克隆（positional cloning）技术分离得到LOS2基因，其编码糖酵解途径中的烯醇化酶（enolase）。在动物细胞中，烯醇化酶还被证实可作为转录因子，通过结合c-myc基因启动子抑制其表达。将LOS2与绿色荧光蛋白（green fluorescent protein）融合后，发现其可靶向定位于细胞核与细胞质中。LOS2/烯醇化酶蛋白能够结合人类c-myc基因启动子的顺式作用元件（cis-element），以及拟南芥锌指转录抑制因子STZ/ZAT10的基因启动子。野生型植株中，STZ/ZAT10的表达会被低温快速且瞬时诱导；而在los2突变体中，该诱导效应更强且持续时间更久。此外，在拟南芥叶片的瞬时表达实验中，STZ/ZAT10可显著抑制RD29A-LUC报告基因的表达。本研究结果证实，植物的低温响应基因转录受到一种双功能烯醇化酶的调控。