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.

As a new generation of molecular diagnostic tools emerged in recent years,the clustered regularly interspaced short palindromic repeats/CRISPR-associated(CRISPR-Cas)systems have been widely used in gene editing,nucleic acid detection,and other fields.Due to its high specificity,high sensitivity,without expensive equipment,simple operation,and inexpensive characteristics in nucleic acid detection,the Cas13a subtype has shown great potential in the field of pathogen detection.This article reviews the mechanism of action of CRISPR-Cas13a,its application in pathogen detection,and related detection methods,and looks forward to the application prospects of Cas13a.To facilitate future investigations on the CRISPR-Cas13a systems and their potential in pathogen detection,this study aims to offer inspiration and serve as a valuable reference.