Question

The purpose for having a beta-glucoronidase (GUS) transgene expressed from 35S CaMV promoter along with the transgene containing LFY (or AP1) gene expressed from 35S CaMV promoter is to:

Question 3 options:

a.	report whether the cells are indeed transformed with the plasmid containing these transgenes
b.	report if the citrus has entered the adult phase
c.	report if the citrus has entered the juvenile phase
d.	report if the LFY (or AP1) has constitutively activated the downstream genes involved in flower production

Answer 1

The purpose for having a beta-glucoronidase (GUS) transgene expressed from 35S CaMV promoter along with the transgene containing LFY (or AP1) gene expressed from 35S CaMV promoter is to:

-report if the LFY (or AP1) has constitutively activated the downstream genes involved in flower production.

• Some trees have a long juvenile phase that delays their reproductive development. To accelerate their flowering time, the juvenile seedlings are being transformed to constitutively express the (LFY) or (AP1) genes, which promote flower initiation.
• LFY is essential to switch from vegetative to reproductive development in dicotyledonous plant species.
• LFY controls the production of the flowers, which are formed instead of secondary inflorescences from the flanks of the shoot apical meristem.
• Because LFY is required for all of the major features that differentiate flowers from inflorescence branches, it is referred to as a meristem identity gene.
• LFY has a dual role as a floral integrator and floral meristem identifier.
• Other meristem identity gene include AP1.
• Assignment of floral fate to lateral meristems is primarily due to the cooperative activity of the flower meristem identity genes (LFY) and (AP1).
• The floral meristem identity genes have two major functions:-
  • First, they give the shoot meristem the ability to produce flowers instead of leaves on its flanks and prevent indeterminate growth of lateral organs.
  • Second, they confer upon the meristem the ability to produce flowers.
• Assignment of flowering and reproduction to lateral meristems is primarily due to the cooperative activity of the flower meristem identity genes, (LFY) and (AP1).
• AP1 expression in lateral meristems is activated by at least two independent pathways, one of which is regulated by LFY.
• AP1, in turn, can positively regulate LFY, because LFY is expressed prematurely in the converted floral meristems of plants constitutively expressing AP1.
• In contrast to this, in shoot meristem, TERMINAL FLOWER1 (TFL1), bars AP1 and LFY expression from the inflorescence shoot meristem.