Abstract
H+-pyrophosphatase (H+-PPase) is a vacuolar membrane proton pump and acidifies vacuoles together with H+-ATPase in plant cells. H+-PPase has two functions: (i) hydrolysis of inorganic pyrophosphate, which inhibits syntheses of macromolecules such as proteins, (ii) transport of protons into vacuoles. So, H+-PPase may play an important role when plants actively synthesize macromolecules and when plants cannot produce enough amount of ATP under anoxia conditions. Thus, we attempted to analyze physiological changes of proton pumps and aquaporins in deepwater rice that has a unique ability to elongate internodes under oxygen-poor deepwater conditions.
Deepwater rice was subjected to deepwater treatment for 1 to 3 days and compared with those without the treatment. As a result, the amount of H+-PPase mRNA and protein increased under deepwater conditions. Also, the amount of some members of TIP, vacuolar type aquaporins, increased remarkably. This means that these molecules may support increase of the vacuolar volume, which leads to cell elongation. Furthermore, other aquaporins having unknown functions showed significant changes under deepwater conditions.
