Result

Vectors construction

We have successfully constructed 2 backbones, piGEM001 and piGEM002. And we have verified them using digestion (Fig.1) and sequencing.

Fig.1 Verification of backbones using digestion A: Digestion the plasmid piGEM001 with HpaI and SpeI. M: DNA marker; 1: plasmid piGEM001 and its digestion product B: Digestion the plasmid piGEM002 with HpaI and DraIII. M: DNA marker; 1: plasmid piGEM002 and its digestion production

Then we have successfully constructed 6 monogene expression vectors, from vector piGEM003 to vector piGEM008. And we have verified all of them using digestion and sequcencing. Here we only show the result of vector piGEM005 (Fig.2).

Fig.2 Digestion the plasmid piGEM005 with EcoRI and SacI. M: DNA marker; 1: piGEM005 plasmid and TCP02-HPS-PHI fragment

In order to enhance the ability of tobacco to metabolize formaldehyde, we have successfully constructed 3 multigenge expression vectors, from vector piGEM009 to vector piGEM011. We have verified all of them using digestion (Fig.3) and sequcencing.

Fig.3 Verification of multi-gene expression vectors using digestion A: Digestion the plasmid piGEM009 with XbaI and SalI. M: DNA marker; 1: piGEM009 plasmid and it's digestion product B: Digestion the plasmid piGEM010 with HindIII and SacI. M: DNA marker; 1: piGEM010 plasmid and it's digestion product C: Digestion of the plasmid piGEM011 with EcoRI and SacI. M: DNA marker; 6: plasmid piGEM011 and it's digestion production

Tobacco transformation

Tobacco was transformed essentially using the leaf disk co-cultivation protocol of Horsch. This protocol includes infection and co-cultivation (Fig.4A), selection (Fig.4B), regeneration and rooting (Fig.4C). We have successfully transformed each vector into babacco and got positive transgenic plantlets (Fig.5). Table 1 is the statistical result of quantity of each transgenic line. And we have got PCR positive plantlets of every transgenic line.

Fig.4 Transform piGEM003, piGEM004, piGEM005, piGEM006, piGEM007, piGEM008, piGEM009, piGEM010 and piGEM011 into tobacco. Co-cultured for 48 hours (A); Selection for one month (B); Rooting for one month (C).

Fig.5 Positive tobacco plantlets of each transgenic line.

Table.1 Statistical result of quantity of each transgenic line.

Expression of four key enzymes in tobacco

We extracted DNA from tobacco plants. And then we used specific primers to amplify the target gene to verify the kan-resistant plants (Fig.6). Next we extracted RNA from tobacco leaves which are PCR positive. We used RT-PCR to detect whether target gene was expressed (Fig.7).

Fig.6 PCR identification of kan-resistant tobacco plants (piGEM010 transgenic line). M: DNA marker; WT: widetype control; P: plasmid; 1-8: 6 individual lines

Fig.7 RT-PCR verification of positive transgenic tobacco plants.

Enhanced formaldehyde tolerance

The transgenic and wildtype plants, which had been grown separately in sealed boxes, were exposed to formaldehyde evaporated from a micro tube (0.5ml) containing formaldehyde solution (37%, 10μl) (Fig.8). Two weeks later we observed the phenotype of transgeneic and widetype plants (Fig.9). We found that the transgenic plant is stronger than wildtype after formaldehyde exposure. This indicates that production of HPS/PHI, FALDH and FDH enhanced formaldehyde tolerance of transgenic plant.

Fig.8 The transgenic (A) and wildtype plants (B), which had been grown separately in sealed boxes, were exposed to formaldehyde evaporated from a micro tube (0.5ml) containing formaldehyde solution (37%, 10μl)

Fig.9 Phenotype testing of transgenic plants and wildtype. A: Before exposure to HCHO. B: Exposure to HCHO for one week. The transgenic plant is stronger than wildtype after formaldehyde exposure. 10μl 37% HCHO, two weeks.

Enhanced formaldehyde absorbance

We detected the concentration of gaseous formaldehyde evaporated from a micro tube (0.5ml) containing formaldehyde solution (37%, 10μl) and made a curve (Fig.10) about relationship between formaldehyde concentration and time. And we saw a linear relationship between formaldehyde concentration and time before formaldehyde is saturated. For quantity result, we used a formaldehyde detector to detect the concentration of gaseous formaldehyde (Fig.11). The transgenic and wildtype plants, which had been grown separately in sealed boxes, were exposed to formaldehyde evaporated from a micro tube (0.5ml) containing formaldehyde solution (37%, 10μl) for about 3 weeks. Three weeks later, the covers of the plant boxes were removed and quickly replaced with covers equipped with formaldehyde dose-monitoring tubes in order to determine roughly the gaseous formaldehyde levels remaining in the boxes. We have not got the precise data results now, and this work is to be continued.

Fig.10 The relationship between formaldehyde concentration and time

Fig.11 Folmaldehyde concentration detection.

Transit peptides affect formaldehyde degrading efficiency

HPS, PHI, and FDH are located in chloroplast, while FALDH plays a role in cytoplasm. So we used transit peptides to locate the productions of these genes. We hope to know the effects of transit peptide on degrading formaldehyde. So we exposed transgenic tobaccos with and without transit peptides to formaldehyde (37%, 10μl). However, there are no obvious phenotype difference compairing different transgenic lines because time limited.

Different genes affect formaldehyde degrading efficiency

To test which enzymes play the most important role in pathway of metabolizing formaldehyde, we constructed mono-gene expression vectors to express each enzyme individually. We also constructed multi-gene expression vectors to test whether the ability of metabolizing formaldehyde of transgenic tobacco enhanced. Then these transgenic tobaccos were exposed to formaldehyde (37%, 10μl). However, we have not got obvious phenotype difference among transgenic lines, because there is not enough time

Tapetal expression of AdCP results in male sterility in high expression plants

Considering the problem of environment and safety, we use male sterility system which prevents the horizontal transgene flow. Morphological and histological analysis of AdCP transgenic plants showed ablated tapetum and complete pollen abortion. However, there is not enough time to wait for transgenic tobacco flowering.