Isolation and characterization of cDNAs and genomic DNAs encoding ADP-glucose pyrophosphorylase large and small subunits from sweet potato.
Sweet potato [Ipomoea batatas (L.) Lam.], the world's seventh most important food crop, is also a major industrial raw material for starch and ethanol production. In the plant starch biosynthesis pathway, ADP-glucose pyrophosphorylase (AGPase) catalyzes the first, rate-limiting step and plays a pivotal role in regulating this process. In spite of the importance of sweet potato as a starch source, only a few studies have focused on the molecular aspects of starch biosynthesis in sweet potato and almost no intensive research has been carried out on the AGPase gene family in this species. In this study, cDNAs encoding two small subunits (SSs) and four large subunits (LSs) of AGPase isoforms were cloned from sweet potato and the genomic organizations of the corresponding AGPase genes were elucidated. Expression pattern analysis revealed that the two SSs were constitutively expressed, whereas the four LSs displayed differential expression patterns in various tissues and at different developmental stages. Co-expression of SSs with different LSs in Escherichia coli yielded eight heterotetramers showing different catalytic activities. Interactions between different SSs and LSs were confirmed by a yeast two-hybrid experiment. Our findings provide comprehensive information about AGPase gene sequences, structures, expression profiles, and subunit interactions in sweet potato. The results can serve as a foundation for elucidation of molecular mechanisms of starch synthesis in tuberous roots, and should contribute to future regulation of starch biosynthesis to improve sweet potato starch yield.
Key Laboratory of Bio-resources and Eco-environment, Ministry of Education, Sichuan Key Laboratory of Molecular Biology and Biotechnology, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
Yu-Xi
YX
Zhou
Key Laboratory of Bio-resources and Eco-environment, Ministry of Education, Sichuan Key Laboratory of Molecular Biology and Biotechnology, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
Yu-Xiang
YX
Chen
Chengdu Institute of Biology, Chinese Academy of Science, Chengdu, 610041, People's Republic of China.
Xiang
X
Tao
Key Laboratory of Bio-resources and Eco-environment, Ministry of Education, Sichuan Key Laboratory of Molecular Biology and Biotechnology, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
Xiao-Jie
XJ
Cheng
Key Laboratory of Bio-resources and Eco-environment, Ministry of Education, Sichuan Key Laboratory of Molecular Biology and Biotechnology, College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China. hayawang@scu.edu.cn.
Hai-Yan
HY
Wang
D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics* / Q000302:isolation & purification; D018506:Gene Expression Regulation, Plant; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000235:genetics* / Q000302:isolation & purification; D027723:Ipomoea batatas / Q000201:enzymology / Q000235:genetics*; D018517:Plant Roots / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics* / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D013213:Starch / Q000096:biosynthesis / Q000235:genetics
D018076:DNA, Complementary; D021122:Protein Subunits; D013213:Starch; D051599:Glucose-1-Phosphate Adenylyltransferase
AGPase; Co-expression; Expression pattern analysis; Starch synthesis; Subunit interactions