University:
The University Of Western Ontario
Course:
Biology 2290F | Scientific Method in Biology
Academic year:

2024
Views:

104

Pages:

2
Author:

Kyuwon J.

Reciprocal Regulation 1. When Sucrose Synthesis is LOW: ○ Reduced Pi generation in the cytoplasm. ○ Less Pi available for Triose-P Translocator. ○ Less Pi enters the chloroplast. ○ Less Triose-P is exported from the chloroplast. ○ Higher 3-PGA:Pi ratio in the chloroplast → Activates ADP-Glucose Pyrophosphorylase (AGPase). ○ Results in HIGH starch synthesis. 2. When Sucrose Synthesis is HIGH: ○ Increased Pi generation in the cytoplasm. ○ More Pi available for Triose-P Translocator. ○ More Pi enters the chloroplast. ○ More Triose-P is exported from the chloroplast. ○ Lower 3-PGA:Pi ratio in the chloroplast → Inhibits AGPase. ○ Results in LOW starch synthesis. 1. Low Rate of Sucrose Synthesis → High Starch Synthesis ● Less Pi is generated in the cytoplasm. ● Less Pi enters the chloroplast via the Triose-P Translocator. ● ● ● ● Less Triose-P exits the chloroplast. High 3-PGA:Pi ratio in the chloroplast. AGPase is activated → More G-1-P is converted to ADP-Glc. High rate of starch synthesis. 2. High Rate of Sucrose Synthesis → Low Starch Synthesis ● ● ● ● ● ● More Pi is generated in the cytoplasm. More Pi enters the chloroplast via the Triose-P Translocator. More Triose-P exits the chloroplast. Low 3-PGA:Pi ratio in the chloroplast. AGPase is inhibited → Less G-1-P is converted to ADP-Glc. Low rate of starch synthesis. Sucrose synthesis and starch synthesis are inversely regulated by phosphate availability. High sucrose synthesis = More Pi in chloroplast = Low starch synthesis. Low sucrose synthesis = Less Pi in chloroplast = High starch synthesis.