Phytoene Synthase Gene ( PSY ) from Sweet Potato ( Ipomoea batatas Lam) Enhances Tolerance to Abiotic Stress

ABSTRACT Phytoene synthase (PSY) is the rate-limiting enzyme for carotenoid biosynthesis. To date, several studies focused on PSY genes in the context of abiotic stress responses. In this study, two phytoene synthase encoding genes, IbPSY1 and IbPSY2, were identified from a published transcriptome and bioinformatic analysis showed that they shared conserved domains with phytoene synthases from other plants. The IbPSY1 gene was cloned and carefully characterized. Digital gene expression profiling (DGE) showed that the highest transcription level of IbPSY1 was in young leaves, and the lowest level was in stems. In vivo expression levels of IbPSY1 under abiotic stress were observed to be highest in stems at day 11. Over-expression of IbPSY1 in Escherichia coli and yeast cells endowed the cells with better growth under salt and drought stress than the control cells. This study demonstrated that IbPSY1 not only played an important role in vivo, but also in E. coli and yeast to improve tolerance to salinity and drought stress. Thus, IbPSY1 may be aid in the development of transgenic plants with enhanced stress tolerance.

Molecular Cloning and Characterization of Phytoene Synthase Gene From a Unicellular Green Alga Haematococcus pluvialis / 生物化学与生物物理进展

The unicellular green alga Haematococcus pluvialis accumulates a highly valuable ketocarotenoid, i.e. astaxanthin up to 4%dry weight under stress conditions. Phytoene synthase is considered to be the first rate limiting enzyme in carotenoid biosynthesis pathway in H. pluvialis. The cDNA and genomic genes of phytoene synthase, i.e. psy from H.pluvialis were cloned and characterized.Result showed that psy had one open reading frame of 1 200 bp encoding a putative polypeptide of 400 amino acids which was interrupted by four introns. Phylogenetic analysis revealed that psy from green algae formed a monophyletic clade, and its closer relationship was higher plants. By using genomic walking approach, an approximate 1 kb 5′ flanking region ofpsy gene was cloned and a number of putative cis-regulatory elements were revealed. Fusing a 297 bp internal sequence (-297 to -1 bp from the translation initiation codon ofpsy) with the reporter gene, i.e. lacZ before attemptedintroducing the construct into the green alga via particle bombardment resulted in lacZ transient expression.