Overexpression of gene GA20ox encoding gibberellin 20-oxidase (GA20-oxidase) in plants has resulted in improved stem elongation and growth rate. However, constitutive overexpression of GA20ox driven by the cauliflower mosaic virus (CaMV) 35S promoter is frequently accompanied by undesirable phenotypes such as poor rooting and small leaves.

 

A study conducted by a team of Vietnamese researchers has determined whether the expression of GA20-oxidase in tobacco (Nicotiana tabacum) would increase stem elongation and enhance xylem formation. The binary vector pBI101 carrying GA20 gene encoding GA20-oxidase (binding c-myc tail) under the control of xylem-specific promoter CAD4 was successfully constructed and transformed into Agrobacterium tumefaciens strain C58.

 

All the transgenic lines showed the xylem-specific expression of GA20-oxidase when using RT-PCR reaction. All 5 selected transgenic tobacco lines exhibited enhanced stem elongation compared to wild type (WT) control lines, the stem heights of transgenic lines increased from 20 to 60% than WT lines. The stem elongation rates of transgenic lines are significantly higher compared to WT. The histological staining of stem cross section showed that all the selected transgenic lines exhibited a substantial increase in xylem differentiation compared to WT, xylem widths of transgenic lines increased from 17-59% than WT. These results confirmed that GA20 affected xylem differentiation and enhanced wood formation.

 

For more information, read the article in the Journal of Science.