Seed-expressed casein kinase I acts as a positive regulator of the SeFAD2 promoter via phosphorylation of the SebHLH transcription factor.
Microsomal oleic acid desaturase (FAD2) catalyzes the first committed step of the biosynthesis of polyunsaturated fatty acids via extra-plastidial desaturation of oleic acid to linoleic acid. In the regulatory mechanism controlling seed-specific SeFAD2 expression, trans-activation of the seed-specific SeFAD2 promoter is mediated by the SebHLH transcription factor (Kim et al. in Plant Mol Biol 64:453-466, 2007). In this study, a protein interacting with SebHLH was isolated from yeast two-hybrid analysis. The protein shares approximately 80% sequence identity with other putative casein kinases and was named SeCKI (Sesame Casein Kinase I). SeCKI transcripts were predominantly expressed in developing sesame seeds and were induced approximately threefold by exogenous application of ABA. eGFP:SeCKI fusion protein was localized to the nucleus. The SeCKI protein specifically bound to SebHLH. The SeCKI protein was autophosphorylated in a calcium-independent manner and transphosphorylated the SebHLH protein. Both the SebHLH and the SeCKI genes or both the SebHLH and mutated SemCKI (K182G) genes, under the control of CaMV 35S promoter, and the GUS reporter gene driven by SeFAD2 promoter containing E- and G-Box motifs were co-expressed in developing sesame seeds. This co-expression revealed that SeCKI enhanced the SebHLH-mediated transactivation of the SeFAD2 gene promoter via phosphorylation of the SebHLH transcription factor.
Kim
Mi Jung
MJ
School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.
Go
Young Sam
YS
Lee
Saet Buyl
SB
Kim
Youn Sung
YS
Shin
Jeong Sheop
JS
Min
Myung Ki
MK
Hwang
Inhwan
I
Suh
Mi Chung
MC
D000595:Amino Acid Sequence; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D047389:Casein Kinase I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D044943:Fatty Acid Desaturases / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009928:Organ Specificity / Q000187:drug effects / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism; D012639:Seeds / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D031685:Sesamum / Q000187:drug effects / Q000196:embryology / Q000201:enzymology* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D020798:Two-Hybrid System Techniques
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D044943:Fatty Acid Desaturases; C040448:delta-12 fatty acid desaturase; D047389:Casein Kinase I; D002118:Calcium