Abstract
Phytochelatins (PCs) play an important role in detoxification of heavy metals in plants. PCs are synthesized from glutathione by phytochelatin synthase (PCS), a dipeptidyltransferase. Sesbania rostrata is a tropical legume plant that can tolerate high concentrations of Cd and Zn. In this study, the S. rostrata PCS gene (SrPCS) and cDNAs were isolated and characterized. Southern blot and sequence analysis revealed that a single copy of the SrPCS gene occurs in the S. rostrata genome, and produces four different SrPCS mRNAs and proteins, SrPCS1–SrPCS4, by alternative splicing of the SrPCS pre-mRNA. The SrPCS1 and SrPCS3 proteins conferred Cd tolerance when expressed in yeast cells, whereas the SrPCS2 and SrPCS4 proteins, which lack the catalytic triad and the N-terminal domains, did not. These results suggested that SrPCS1 and SrPCS3 have potential applications in genetic engineering of plants for enhancing heavy metal tolerance and phytoremediation of contaminated soils.
Highlights
Phytochelatins (PCs) have been found in all plant species investigated, a few fungal species and some marine diatoms [1]
In order to study the structure of S. rostrata phytochelatin synthase (PCS) gene (SrPCS), we cloned the genomic sequence of SrPCS from the genomic DNA of S. rostrata by genome walking [28] with primers based on the conserved sequence of SrPCS1-4 cDNAs
We found that a single copy of the SrPCS gene occurs in S. rostrata genome, and that alternative splicing of the SrPCS pre-mRNA produced four different SrPCS mRNAs and proteins, SrPCS1−SrPCS4 (Figure 1)
Summary
Phytochelatins (PCs) have been found in all plant species investigated, a few fungal species and some marine diatoms [1]. PCs have the general structure (γ-Glu-Cys)n-Gly, where n has been reported to be as high as 11, but generally ranges from 2 to 5 [4]; they are synthesized posttranslationally in the presence of heavy metal ions from glutathione (GSH) by PC synthase (PCS), a γ-glutamyl-cysteine transpeptidase [5]. This study represented the first crystal structure of a PCS and established that prokaryotic NsPCS and the eukaryotic Arabidopsis thaliana PC synthase (AtPCS1) belong to the papain superfamily of cysteine proteases, with a conserved catalytic machinery that had been deduced from kinetic, protein chemical, and site mutagenic studies of the prototypical AtPCS1 [8,10,15]. It has been proposed that PCS is a constitutive enzyme in general and its gene expression is not induced in response to heavy metal exposure [23]. To understand the mechanism of heavy metal tolerance in S. rostrata, in this study the corresponding PCS gene and its cDNAs were isolated and characterized
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
