Reference "Rice SPK, a calmodulin-like domain protein kinase, is required for storage product accumulation during seed development: phosphorylation of sucrose synthase is a possible factor"

Reference ID

6603

Title

Rice SPK, a calmodulin-like domain protein kinase, is required for storage product accumulation during seed development: phosphorylation of sucrose synthase is a possible factor

Source

The Plant cell, 2002, vol. 14, pp. 619-628

Authors (14)

Asano-T	Kunieda-N	Omura-Y	Ibe-H
Kawasaki-T	Takano-M	Sato-M	Furuhashi-H
Mujin-T	Takaiwa-F	Tada-Y	Satozawa-T
Sakamoto-M	Shimada-H

Abstract

Suc, an end product of photosynthesis, is metabolized by Suc synthase in sink
organs as an initial step in the biosynthesis of storage products. Suc synthase
activity is known to be regulated by reversible phosphorylation, but the details
of this process are unclear at present. Rice SPK, a calcium-dependent protein
kinase, is expressed uniquely in the endosperm of immature seed, and its
involvement in the biosynthetic pathways of storage products was suggested.
Antisense SPK transformants lacked the ability to accumulate storage products
such as starch, but produced watery seed with a large amount of Suc instead, as
the result of an inhibition of Suc degradation. Analysis of in vitro
phosphorylation indicated that SPK phosphorylated specifically a Ser residue in
Suc synthase that has been shown to be important for its activity in the
degradation of Suc. This finding suggests that SPK is involved in the activation
of Suc synthase. It appears that SPK is a Suc synthase kinase that may be
important for supplying substrates for the biosynthesis of storage products.