Enhanced Drought and Salinity Tolerance in Transgenic Potato Plants with a BADH Gene From Spinach
by Caitlin McGarry (42945080)
Water, salinity, temperature and light are the major abiotic stress conditions that hinder production of the economically important crops such as wheat, maize, oat and potato (Peleg, Apse & Blumwald 2011, Evers et al. 2007). As a result of the expanding global population, it is imperative to explore ways to improve the production of these essential crops under abiotic stress conditions, such as drought and salinity, to cater for the world’s population (Peleg, Apse & Blumwald 2011). In relation to the potato, one study by Zhang et al. (2011) involved introducing a betaine aldehyde dehydrogenase (BADH) gene from spinach into the potato, improving it’s tolerance to salinity and drought.
Glycine betaine (GB) has been studied in depth and is known to be involved in protecting plants against certain abiotic stresses, which include salt and water deficiency (Fitzgerald, Waters & Henry 2009). GB is synthesised from betaine aldehyde (BA) in many plants in response to stress through a two-step oxidation pathway involving the enzyme BADH (Si, Zhang & Wang 2012, Liu et al. 2011). A gene has been identified that encodes for this protein BADH with the known enzymatic function of synthesising GB from BA (Liu et al. 2011, Zhang et al. 2011). Therefore, it is believed the BADH gene is an essential component of a plant’s response to drought and salinity.
The potato is moderately affected by salinity and drought and is also low in betaine levels, therefore the study by Zhang et al. (2011) attempted to improve tolerance to these stresses by introducing the BADH gene (Si, Zhang & Wang 2012, Zhang et al. 2011). Following traditional cultivation techniques to improve potato crops take time and the results are often uncertain due to the quantitative inheritance of the potato and it’s polyploidy nature (Si, Zhang & Wang 2012).Therefore, genetic engineering is a potential avenue to provide a quick and accurate means of improving crop tolerance to salinity and drought (Si, Zhang & Wang 2012). The 1,556 base pair DNA that encodes for the BADH enzyme was isolated from the spinach using reverse transcription-polymerase chain reaction and inserted into the SmaI-SacI site of the plasmid pBIrd, along with the rd29A promoter. The resultant recombinant plasmid was called pBIrB, as shown in Figure 1 (Zhang et al. 2011). The recombinant plasmid was then added to the bacteria, Agrobacterium tumefaciens, for amplification (Zhang et al. 2011).
Figure 1 – Recombinant pBIrB plasmid with BADH insert (Zhang et al. 2011).
The effectiveness of introducing this gene encoding for BADH into the potato was analysed by comparing the transgenic plants under normal, salinity and drought conditions to control plants. The plants were treated with NaCl and Polyethylene Glycol (PEG), a drought simulation, and several outcomes were observed. Firstly, the BADH activity levels post treatment with NaCl and PEG were high in the transgenic plants, who were less effected by NaCl and PEG treatment, and zero levels were detected in the control plants, who were more affected by treatment (Zhang et al. 2011). The results also showed that the growth of the transgenic plants were better that the control plants after NaCl and PEG treatment with the transgenic plants being 0.4-0.9cm taller and 17-29% heavier (Zhang et al. 2011). Figures 2 and 3 compare the height and weight of the control and the transgenic plants.
Figure 2 – Heights of transgenic potato plants 3 days after a 10 day treatment of NaCl and PEG. Plant C is the nontransgenic potato plant and plants 1-4 are the transgenic potato plants (Zhang et al. 2011).
Figure 3 – Weights of transgenic potato plants 3 days after a 10 day treatment of NaCl and PEG. Plant C is the nontransgenic potato plant and plants 1-4 are the transgenic potato plants (Zhang et al. 2011).
Overall this method shows great potentials for not only improving resistance to salinity and drought in the potato and other crops. For example, genetic manipulation could lead to ongoing improvements in other areas such as pest resistance, disease resistance, improved post-harvest storage, flavour, nutrition, shape and colour (Si, Zhang & Wang 2012). Based on this study, further research should be conducted to examine in depth the effects, both benefits and disadvantages, of introducing the BADH gene into the potato.
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