Expression profiles of PtrLOS2 encoding an enolase required for cold-responsive gene transcription from trifoliate orange

Abstract

Low expression of osmotically responsive genes 2 (LOS2) encodes an enolase (2-phospho-D-glycerate hydrolase, EC 4.2.1.11) that converts 2-phospho-D-glycerate (PGA) to phosphoenolpyruvate (PEP) in the glycolytic pathway in Arabidopsis. Meanwhile, it is a transcriptional activator of cold-responsive gene, negatively controlling the expression of STZ/ZAT10, a zinc finger transcriptional repressor of cold-responsive gene from Arabidopsis. A novel LOS2 gene, designated PtrLOS2 (GenBank accession number GQ144341), was isolated from trifoliate orange [Poncirus trifoliata (L.) Raf.]. The PtrLOS2 cDNA is 1 662 bp in length with a 1 338 bp open reading frame (ORF), encoding a deduced 445 amino acid residue protein with a predicted molecular mass of 47.79 kDa and an isoelectric point of 5.54. The deduced protein of the PtrLOS2 gene shares high identity (over 86 %) with other plant species enolase, which suggests that the PtrLOS2 probably encodes an enolase. Sequence alignment showed that PtrLOS2 protein has a conserved DNA-binding and a repression domain. Moreover, a conserved start site of alternative translation for the c-myc promoter binding protein (MBP-1) was also found in PtrLOS2 protein. PtrLOS2 was constitutively expressed in leaves, stems and roots. PtrLOS2 expression in roots and stems was much higher than that in leaves under normal conditions, however, the expression of PtrLOS2 was up-regulated in leaves, but down-regulated in roots after cold treatments. The PtrLOS2 expression in stems was firstly up-regulated and then down-regulated after cold treatments. Meanwhile, after ABA treatment, the expression of PtrLOS2 was up-regulated in leaves but in stems and roots firstly down-regulated followed with up-regulation.