Difference between revisions of "Part:BBa K4653001"

Revision as of 12:20, 4 October 2023

shRNA(CHSIIIa)-1

In order to kill B. cinerea, the pathogen of grey mold and control the disease in tomato, we designed two pieces of shRNAs targeting the CHSIIIa gene of the pathogen, which is essential for its cell wall formation, based on RNAi technology. shRNA can be actively absorbed by B. cinerea, then enter into its cells to be processed into siRNA, and further specifically target mRNA to achieve degradation. Or, entering plant cells, the related proteins in the cell will process and deliver shRNAs to B. cinerea, which can also achieve the effect of silencing mRNA, reducing the level of its specific protein, and finally forming the inhibition of the pathogen.

Essential information

Sequencing

Sequence and Features

Biology

Chitin synthase (CHS) catalyzes the synthesis of chitin, a major structural component of fungal cell walls consisting of β-1, 4-linked N-acetylglucosamine polymers. CHS can be divided into seven classes, and ascomycetes usually have representatives of all seven classes, with each enzyme having a specific role. CHS (III, V, and VI) are specific to molds, suggesting that they may play an important role in hyphal growth. Like other ascomycetes, B. cinerea contains two CHSIII genes. It has been shown that the BcchsIIIa gene is most expressed in the CHSIII genes, whereas the BcchsIIIb gene is not expressed in any of the growth conditions used. By silencing the important chitin synthase gene BcCHSIIIa, the formation of the cell wall of B. cinerea could be affected, thus killing pathogenic fungi.

Design of shRNA

After confirming the selection of targets BcCHSIIIa, we searched the cDNA library of B. cinerea according to the sequences or primes provided in the literature, and found the homologous cDNA sequence of B. cinerea. Then, the sequence was input into the National Center for Biotechnology Information (NCBI) website for analysis and prediction, and the CDS sequence of the target gene was input into the total nucleic acid database BLAST to query the homologous similarity of neighboring species. siRNA sequences were designed in non-conserved regions to ensure species-specific and biosafety of our shRNAs.

Next, we used a professional siRNA designed website ( https://www.genscript.com/tools/sirna-target-finder) to predict the siRNA sequences that would effectively target the mRNA, and then screened out siRNA fragments with high potential activity in a series of predictions based on shRNA design principles. By making structural predictions of the mRNA (http://rna.tbi.univie.ac.at/cgi-bin/RNAWebSuite/RNAfold.cgi), we ensured that the selected siRNA sequences targeted relatively loose positions in the mRNA structure. For biosafety reasons, we BLAST the candidate siRNA fragments into the total mRNA database to ensure that it does not target any genes of common species (such as human, tomato, dog, rice, wheat, etc.), ensuring sequence specificity.

Finally, we assembled the selected siRNA sequence into our shRNA in the sequence of siRNA sense strand - loop - reversed siRNA antisense strand.

Plasmid construction

We have assembled our shRNA in the sequence of siRNA sense strand - loop - reversed siRNA antisense strand, then sequence was assembled in the pET28a (+) plasmid. The recombinant vector was transferred into RNase-deficient E. coli HT115(DE3), and the large-scale fermentation production of shRNA in E. coli could be achieved by induction of IPTG. In our experiment, the results of treatment of different shRNAs at both phenotypic and molecular levels were analyzed to screen out the effective shRNAs.

Usage

The shRNA(CHSIIIa) will be used in crop protection through the way of spraying induced gene silencing (SIGS), which is an emerging, non transgenic RNAi strategy. After screening out an effective shRNA against B. cinerea, the shRNA will be wrapped in KH9-BP100, which belongs to cell-penetrating peptides in a spherical shape and can be used to deliver biological molecules, to forming a CPP-shRNA complex. Then, spraying the complex on the tomato infected by B. cinerea, we hope that it can play a more effective and more steady role in controlling grey mold.

Characterization

shRNA production induced by IPTG

After plasmid extraction, we transformed the constructed shRNA expression vector into E.coli HT115 (DE3) and performed PCR. Our specific primers successfully amplified a 260 bp band from the plasmid, confirming the successful transformation of the plasmid. This indicates that the shRNA expression vector has been successfully introduced into E.coli and can be detected and confirmed by PCR. This is an important milestone that lays the foundation for further experiments.