The phosphatase/kinase balance affects phytochrome A and its native pools, phyA′ and phyA″, in etiolated maize roots: evidence from the induction of phyA′ destruction by a protein phosphatase inhibitor sodium fluoride

Abstract

Phytochrome A (phyA) comprises two native types, phyA′ and phyA″, with distinct spectroscopic, photochemical, and functional properties, differing at the N-terminal extension, probably, by the state of phosphorylation. To find out if and how protein phosphatases (PP) affect the state of the phyA species in planta, we studied the effect of the non-specific phosphatase inhibitor NaF on etiolated maize seedlings with the use of low-temperature fluorescence spectroscopy and photochemistry. In roots, phosphatase inhibition facilitated photoreceptor destruction in its labile phyA′ form and shifted the phyA′/phyA″ ratio towards the more stable phyA″. The effect of NaF was not observed in stems. It was similar, though less pronounced, in comparison to the effects of the serine/threonine PP inhibitors, okadaic and cantharidic acids (OA and CA), which likewise facilitate the destruction of phyA′ in etiolated maize stems, not, however, in roots (Sineshchekov et al., Photochem. Photobiol 89:83-96, 2013). The phyA′/phyA″ balance thus depends on the kinase/phosphatase equilibrium in the root cells. The relatively low effect of NaF on phyA in roots, together with the lack of the effect of OA and CA in them, may imply that the mechanism controlling the phyA′/phyA″ balance in roots can be different from that in shoots.

Two Distinct Molecular Types of Phytochrome A in Plants: Evidence of Existence and Implications for Functioning

“…This is evidenced by the lack of the effect of the Ser8Ala and Ser18Ala substitutions on the phyA'/phyA″ balance [86]. Besides, the treatment of etiolated maize seedlings by okadaik (OA) and cantaridic (CA) acids (in stems) and by NaF (in roots) shifting the phosphatase/kinase equilibrium towards the former results in the increase of the phyA″ proportion, although one could expect to get more phyA′ at the expense of phyA″ (see [71,88] and discussion of this issue below). However, the option that some other serine(s) in the NTE serine cluster besides Ser8 and Ser18 is phosphorylated to form phyA′ from phyA″ is still open, and the nature of the mechanism of the phyA'/phyA″ interconversion needs further investigation.…”

“…The mechanisms determining this complex behaviour of phyAs remain unclear, although there are indications that the phosphatase/kinase equilibrium in the cell and cytoplasmic pH affect it [71,88]. The agents suppressing phosphatase activity and shifting the phosphatase/kinase equilibrium towards kinases (okadaic and cantaridic acids-inhibitors of phosphatases of the PP1 and PP2A types, and NaF-phosphatase inhibitor of a broad spectrum) brought about the increase in the phyA content relative to that of phyA due to the elevated destruction of the latter or its conversion into phyA .…”

An in‐silico investigation of fluoride ions impact on pancreatic lipase

“…Majority of fluoride protein interactions are through either (1) fluoride binding to an essential metal in a metalloprotein's active site, or (2) the complexing of fluoride with metal and acting as a substrate mimic. [4][5][6] On the other hand, there are studies which show that the fluoride interacts with enzymes Aconitase, 7 Adenylyl cyclase, 8 Arginase, 9 Cytochrome-coxidase, 10 Glucose-6-phosphatase, 11 Protein phosphatase, 12 Succinate dehydrogenase 13 from liver and lipase 14 from pancreas.…”