Select, create and evaluate promising fast-growing transgenic Xoan lines
Enhancement of GA20 oxidase gene expression is a promising modality to improve plant growth and biomass. Many studies show that increasing the expression of the GA20ox gene helps plants to grow better, improving biomass. However, overexpression of this gene can cause undesirable phenotypes, such as reduced leaf size and stem diameter.
To limit these effects, scientists from the Institute of Biotechnology have studied and used the At1g promoter with root-specific expression (At1g) to control the expression of the AtGA20ox gene. The specificity of root expression of this promoter was confirmed by GUS staining and realtime-PCR in GUS transgenic tobacco lines (Figure 1).
Figure 1. Expression of the GUS gene in transgenic tobacco plants
The expression of GUS gene in different tissues including roots, stem and leaf cross sections of non-transgenic tobacco plants, At1g::GUS transgenic lines and 35S::GUS transgenic lines. B Levels of gus gene expression in transgenic tobacco lines. The results of real-time-PCR (top) and RT-PCR (bottom) evaluate the level of gus and actin gene expression at root apex, root, stem and leaf apex. * represents a significant difference with P < 0.05 (n = 3). NtAct (Nicotiana tabacum actin gene) was used as the reference gene.
Enhancing the expression of the AtGA20ox gene under the control of the At1g promoter helps tobacco plants and Xoan plants grow well and increase biomass (Figure 2). Stem height as well as fresh weight of stem and roots increased up to 1.5-3 times in transgenic tobacco and 2 times in transgenic Xoan compared with non-transgenic plants. Both the transgenic tobacco and Xoan plants showed an increase in root xylem width with a xylem to phloem ratio of over 150%-200% compared with WT plants. In particular, there were no phenotypic abnormalities of At1g::AtGA20ox transgenic plants. These results demonstrate the great potential of the At1g promoter in enhancing AtGA20ox gene expression to enhance growth and improve biomass in woody plants and some other plant species.
Figure 2. Morphological characteristics of transgenic tobacco lines.
Plant height (A), fresh weight of stem (B) and root (C) of transgenic tobacco lines. Different letters represent a significant difference with P < 0.05 (n = 5). Plant height (D), fresh weight of stem (E) and root (F), cross section of roots stained with toluidine blue (G) of Xoan transgenic lines.
The crossbar is equivalent to 1000 µm; * represents a significant difference with P < 0.05 (n = 5). WT: non-transgenic plants; A5, A7, A9: transgenic tobacco lines At1g::GA20ox; S2, S5: 35S::GA20ox transgenic tobacco lines; A1, A5, A14: the Xoan transgenic lines At1g::GA20ox.
Scientific significance: Research results confirm the potential of using specific promoters to control the GA20ox gene in research to improve growth and biomass in plants. Isolated genes, engineered transgenic vector structures, and Agrobacterium tumefaciens strains containing transgenic vector structures can be used for further research on subjects on other crops, especially forestry trees.
Socio-economic significance: Existing transgenic plant lines will be the raw materials for the selection and development of fast-growing Xoan lines to serve the development of production forests. The Xoan transgenic lines with high yield, high quality, strong roots capable of growing quickly on nutrient-poor soil have the potential to improve the efficiency of afforestation for ethnic minorities in mountainous terrain, contributing to poverty alleviation and development of the wood processing industry.
Prospects for replicating the results/products in the future: The Xoan transgenic lines which have good roots and fast growth will continue to be planted for trial or transferred to forestry plant varieties research units under the Ministry of Agriculture and Rural Development to assess biosecurity, plant trials, and recognition of new varieties.
Translated by Tuyet Nhung
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