64. The GA2-oxidase gene from bean is overexpressed in a wheat plant by geneticengineering. Which
one of the following phenotypes correctly describes the resultanttransgenic plant?
(a) The height of the plant will not be affected
(b) The plant will be shorter than the wild type
(c) The plant will be taller than the wild type
(d) The plant will not survive

GA2-Oxidase Overexpression: Engineering Dwarfism in Wheat Plants

In genetic engineering, manipulating hormone pathways can lead to significant changes in plant architecture. One key player in plant growth regulation is gibberellin (GA), a hormone that promotes stem elongation. The enzyme GA2-oxidase plays a critical role in deactivating gibberellins. Therefore, overexpressing this gene can significantly influence plant height.

Correct Answer:

(b) The plant will be shorter than the wild type

How GA2-Oxidase Affects Plant Growth

GA2-oxidase enzymes catalyze the inactivation of bioactive gibberellins by converting them into inactive forms. By overexpressing this gene in wheat:

• Active GA levels decrease.

• Cell elongation and stem growth are reduced.

• The plant exhibits a dwarf or semi-dwarf phenotype.

Why Engineer Dwarf Plants?

Dwarf varieties are often more resistant to lodging (falling over) and are better suited for high-yield agriculture, especially in cereal crops like wheat and rice. The “Green Revolution” prominently featured semi-dwarf wheat and rice, which contributed to massive global increases in food production.

Explanation of Other Options:

• (a): The height will indeed be affected, so this is incorrect.

• (c): Opposite of what occurs; reducing GA activity shortens the plant.

• (d): Overexpression of GA2-oxidase does not typically impair viability.

Conclusion

By genetically engineering wheat to overexpress the GA2-oxidase gene from beans, researchers can create shorter plants that may offer agricultural advantages. This strategy highlights how hormone modulation can be harnessed for crop improvement.