Applet Human Practices Experiment Project Team Awards

Procedure

Construction of plasmid vector

We used the fungal plasmid pBC (donated from professor Xie) for our project, which can propagate in Metarhizium anisopliae 128. The vector contains the following parts:

Gene	Description
PgpdA	PgpdA is the constitutive promoter of the glyceraldehyde-3-phosphate dehydrogenase gene (gpdA) from Aspergillus nidulans.
TtrpC	TtrpC is a tryptophan terminator from Aspergillus nidulans.
HsbA	Encoded by the gene HsbA from Beauveria bassiana ARSEF 2860.
Bbchit	Encoded by the gene Bbchit from Beauveria bassiana ARSEF 2860.
MCL1	MCL1_Metarhizium robertsii ARSEF 23
Tryptophan-MazF	Suicide switch, induces apoptosis in the absence of tryptophan.

Inside the vectors，there are four gene pathways. PgpdA promoter starts the transcription of HsbA, Bbchit, MCL1, Ttyptophan-MazF. And TtrpC terminator terminates the transcription. It is well to be reminded that the pathway, PgpdA-Ttyptophan-MazF-TtrpC has a special switch, which induces apoptosis in the absence of tryptophan.

The model organism used in the project is Metarhizium anisopliae 128 (presented by professor Zhongkang Wang from Chongqing University), which is a major strain of Metarhizium anisopliae 128 with strong virulence.

Transformation and expression

We used the transformation method of Xiaoling Wang to transform Metarhizium anisopliae 128, and obtained stable transformant through the screening of G418 sulfate, and then verified the successful transformation through extracting genome, primer PCR and nucleic acid electrophoresis.

HsbA

To verify the existence and function of HsbA protein, the following treatment is done.

The transformed strain Metarhizium anisopliae 128 was grown in 1/4 SDAY liquid medium, and obtain total protein by smashing cells with FastPrep and ultrasonic crushing. And then we detected the native molecular mass by SDS-PAGE and coomassie blue staining. Besides, we spread the spores of Metarhizium anisopliae 128 and Metarhizium anisopliae HsbA transformant onto the cockroaches’ legs. After 16h germination, we took out and placed the cockroaches’ legs on the scanning electron microscope for observation. Then we rinsed the observed area on the cockroaches’ legs with 200ul ddH₂O and observed them on the microscope again. Finally, we can compare whether there is any change in the position and number of spores in the observing area.

Bbchit

In order to verify the function of the transferred chitinase, the following experiments were performed.

The wild-type Metarhizium anisopliae 128 and Bbchit transformant were cultured in 1/4 SDAY liquid medium, and obtained the crude enzyme solution by smashing cells with FastPrep and ultrasonic crushing. Then, the native molecular mass of protein was detected by SDS-PAGE and Coomassie staining. In addition, to verify the enzyme activity, we used Czapek culture medium to culture the wild type and the modified type and took bacteria medium of 1, 3, 5, 7, 9 and 12 days to filter and obtain the crude enzyme solution. We optimized the method of Kan Zhuo‘s and Xiaozhen Shi’s to chart the chitinase activity curve through DNS colorimetry. At the macro level, using the method of transparent circle, we verified that our transferred chitinase can strongly penetrate the chitin of body surface of cockroach.

MCL1

Application and realizztion

In order to make our Metarhizium anisopliae spores into products, we designed GreenGround, a containing box for spores, with a structure similar to the cockroach house.

Compared to regular chemicals, GreenGround reduces the elimination of cockroaches. To prove its usefulness, we built a simulated room to test it. But according to the principle of no release, we could not use the modified Metarhizium anisopliae. So in the experiment we used the wild type Metarhizium anisopliae.

We built two mini-houses using KT Board (made of polystyrene) to simulate two rooms, which connected with a corridor. We design blank group without any drugs, and experimental group with cockroach killing chalk, BAYER-Premise and out product equipped with M.anisopliae emulsifiable powder. Then, we put thirty cockroaches into one room each time, and came back to see the results after three days. We focused more attention on migration rate and mortality. Finally, we got results that the migration rate of blank group was 7.78%, while 21.11%, 20.00%, 6.67% respectively in groups using cockroach killing chalk, BAYER-Premise and our product. For mortality in three days, 77.78% in group using chalk, 84.44% in group using Premise, 85.56% in group using our product, and 2.01% in group using nothing. Statistical Analysis in our model shows our product with M.anisopliae emulsifiable powder will not cause a high migration rate of cockroaches comparing with traditional products, at the same time, it has similar mortality.

	Migration Rate	Mortality	Gnawing Rate
Cockroach killing chalk	21.11%	77.78%	2.22%
M.anisopliae	6.67%	85.56%	11.11%
Blank group	7.78%	1.11%	1.11%r