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

10.751
Takayuki Asano, Noriko Kunieda, Yuhi Omura, Hirokazu Ibe, Tsutomu Kawasaki, Makoto Takanoc, Miho Sato, Hideyuki Furuhashi, Toshiyuki Mujin, Fumio Takaiwa, Chuan-yin Wu, Yuichi Tada, Tomomi Satozawa, Masahiro Sakamoto, Hiroaki Shimada
The Plant Cell, 2002, 14(3): 619-628  DOI: 10.1105/tpc.010454;      追溯原文......本站官方QQ群:62473826

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.

水稻一个钙调蛋白样结构域蛋白激酶SPK是种子发育时储藏产物积累所必需的,磷酸化蔗糖合酶可能是其作用的一个因子

蔗糖作为光合作用的终产物,通过蔗糖合酶进行蔗糖代谢是库器官贮藏物质生物合成的第一步反应。蔗糖合酶的活性受到可逆的磷酸化作用调节,但关于这一过程的具体细节还不是很清楚。一个水稻钙依赖性蛋白激酶SPK,特异在未成熟种子的胚乳中表达,推测其可能参与了贮藏物质的生物合成。反义表达SPK的转基因植株缺少积累诸如淀粉等贮藏物质的能力,由于蔗糖的降解被抑制,只能形成蔗糖含量高的水一样的种子。体外磷酸化分析发现,SPK对蔗糖合酶丝氨酸残基有特异的磷酸化作用,这对蔗糖降解中蔗糖合酶的活性是必需的。结果表明SPK参与了蔗糖合酶的活化。作为一个蔗糖合酶激酶,SPK在为贮藏物质生物合成提供底物的过程中发挥着重要的作用。


基因列表
  蔗糖合酶激酶; 钙依赖性蛋白激酶 SPK