Vitaly Sineshchekov, Larissa Koppel, Ekaterina Shor, Galina Kochetova, Paul Galland and Mathias Zeidler Protein Phosphatase Activity and Acidic/Alkaline Balance as Factors Regulating the State of Phytochrome A and its Two Native Pools in the Plant Cell Photochemistry and Photobiology 89
Phytochrome A (phyA) exists in two forms, phyA′ and phyA′′, what may explain the diverse modes of its action. With the use of phyA fluorescence and photochemistry, it was shown that [phyA′]/[phyA′′] in etiolated maize tissues correlated with their pH. Inhibition of the PP1 and PP2A phosphatases with okadaic and cantharidic acids brought about phyA′ decline and/or concomitant increase of phyA′′ in coleoptiles and mesocotyls (see Figure), but had no effect in roots. Thus, pH and phosphorylation status may regulate [phyA′]/[phyA″] via alteration of the processes of phyA′ destruction and/or its transformation into the more stable phyA″.
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