The SnRK1A protein kinase plays a key role in sugar signaling during germination and seedling growth of rice.
Sugars repress alpha-amylase expression in germinating embryos and cell cultures of rice (Oryza sativa) through a sugar response complex (SRC) in alpha-amylase gene promoters and its interacting transcription factor MYBS1. The Snf1 protein kinase is required for the derepression of glucose-repressible genes in yeast. In this study, we explored the role of the yeast Snf1 ortholog in rice, SnRK1, in sugar signaling and plant growth. Rice embryo transient expression assays indicated that SnRK1A and SnRK1B act upstream and relieve glucose repression of MYBS1 and alphaAmy3 SRC promoters. Both SnRK1s contain N-terminal kinase domains serving as activators and C-terminal regulatory domains as dominant negative regulators of SRC. The accumulation and activity of SnRK1A was regulated by sugars posttranscriptionally, and SnRK1A relieved glucose repression specifically through the TA box in SRC. A transgenic RNA interference approach indicated that SnRK1A is also necessary for the activation of MYBS1 and alphaAmy3 expression under glucose starvation. Two mutants of SnRK1s, snrk1a and snrk1b, were obtained, and the functions of both SnRK1s were further studied. Our studies demonstrated that SnRK1A is an important intermediate in the sugar signaling cascade, functioning upstream from the interaction between MYBS1 and alphaAmy3 SRC and playing a key role in regulating seed germination and seedling growth in rice.
Lu
Chung-An
CA
Department of Life Sciences, National Central University, Jhongli City, Taoyuan County 320, Taiwan, Republic of China.
Lin
Chih-Cheng
CC
Lee
Kuo-Wei
KW
Chen
Jyh-Long
JL
Huang
Li-Fen
LF
Ho
Shin-Lon
SL
Liu
Hsin-Ju
HJ
Hsing
Yue-Ie
YI
Yu
Su-May
SM
D050260:Carbohydrate Metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination; D008954:Models, Biological; D009154:Mutation; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012045:Regulatory Sequences, Nucleic Acid; D036226:Seedlings / Q000201:enzymology* / Q000254:growth & development*; D015398:Signal Transduction; D013379:Substrate Specificity; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D010940:Plant Proteins