2007 Fiscal Year Final Research Report Summary
Functional analysis of MLPK, a membrane-anchored cytosolic protein kinase, in Brassica self-incompatibility signaling
| Project/Area Number |
18380069
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Applied biochemistry
|
|---|
| Research Institution | Nara Institute of Science and Technology |
|---|
Principal Investigator |
TAKAYAMA Seiji Nara Institute of Science and Technology, GRADUATE SCHOOL OF BIOLOGICAL SCIENCES, PROFESSOR (70273836)
|
|---|
| Project Period (FY) |
2006 – 2007
|
| Keywords | self-incom atibilitv / signal transduction / Brassica / kinase / two-hybrid / 自家不和合性 / アブラナ科 / シロイヌナズナ |
|---|
| Research Abstract |
The aim of the present study was to evaluate the functional role of MLPK, a membrane-anchored cytosolic protein kinase found as a causal factor of a self-compatible Brassica mutant. The major findings are summarized as follows.
1. Molecular function of MLPK.
We identified two different MLPK transcripts, MLPKf1 and MLPKf2, which are produced by using alternative transcriptional initiation sites and encode two isoforms that differ only at the N-termini. Both MLPKf1 and MLPKf2 are expressed in papilla cells and localize to the plasma membrane by different molecular mechanisms. Although both MLPKPf1 and MLPKf2 could independently complement the mlpk/mlpk mutation, their mutant forms that lack the plasma membrane localization motifs failed to complement the mutation. Furthermore, a bimolecular fluorescence complementation (BiFC) assay revealed direct interactions between SRK and the MLPK isoforms in planta. These results suggest that MLPK isoforms localize to the papilla cell membrane and interact directly with SRK to transduce SI signaling.
2.Target molecule of MLPK
We searched for MLPK-interacting stigmatic proteins by yeast two-hybrid screening and found several candidates. Some candidates were found to selectively interact with active form of MLPK, and were shown to be specifically phosphorylated by the recombinant MLPK in vitro. We are now trying to elucidate the physiological function of these candidate molecules.
Arabidopsis thaliana is a self-compatible Brassica plant having an MLPK ortholog, APK1b. To test for biological functions of APK1b aside from SI signal transduction, we analyzed a T-DNA knockout line for APK1b: we failed, however, to detect any phenotypic alterations including fertility. The sole function of APK1b in SI signal transduction or the redundancy with regard to homologous kinases might explain the lack of aberrant phenotype in knockout mutant of APK1b.
|
