CKI1, a putative sensor histidine kinase is essential for proper female gametophyte formation in Arabidopsis thaliana.
|Year of publication||2004|
|Type||Article in Proceedings|
|Conference||Boook of Abstracts, Cytokinematics 2004, Microscopy of Live Cells in the Post Genomics Era. The 8th Symposium on Light Microscopy & Live Cells in Hradec Kralove|
|MU Faculty or unit|
|Field||Genetics and molecular biology|
|Keywords||female gametophyte development; two-component signaling; sensor histidine kinase; early seed development; genomic imprinting|
|Description||Embryo sac formation is a fundamental step in plant sexual reproduction. However, the key players driving female gametophyte development remain elusive. Employing reverse genetics, we have identified CKI1, a putative sensor histidine kinase, as a key regulatory component during female gametophyte formation in Arabidopsis thaliana. Using PCR-based screen we have identified a line carrying insertion of the autonomous transposable element En-1 in the coding region of CKI1 gene. Distorted genotype ratios and distribution of the insertional mutant allele cki1-i in the progeny of the identified mutant plant suggested lowered viability and/or function of the cki1-i gametes. In accordance to that, the results of reciprocal back-crosses have shown that cki1-i cannot be transmitted through the female germ line. Confocal laser scanning microscopy (CLSM) analysis of developing embryo sacs from cki1-i/CKI1 pistils did not reveal any deviations from the wild type phenotype in the first four developmental stages of megagametogenesis, FG1 through FG4. First anatomically distinguishable defects (distortion of the central vacuole, changes in the nuclei positions and partial degradation of the embryo sac) were identified in late FG5. The results of CLSM analysis 24 hours after flower emasculation (HAE) have confirmed that half of the embryo sacs from cki1-i/CKI1 pistils are unable to develop beyond the FG5. CLSM analysis 48 HAE revealed dynamic nature of the progressive degradation of mutant embryo sacs, very probably as a result of the central vacuole disintegration. The transcriptional activity of CKI1 during megagametogenesis was identified using in situ CKI1 mRNA analysis on paraffin sections of the developing embryo sacs. We have found weak but distinct signal throughout the embryo sac development, suggesting very early transcriptional activation of CKI1 during megagametogenesis. The results were confirmed by the histochemical analysis of stable transformants carrying fusion of the CKI1 promoter region with marker gene uidA. The GUS activity in developing embryo sacs was detectable as early as in the FG1 and remained detectable throughout megagametogenesis, even after the embryo sacs reached complete maturity at FG7. CKI1 expression was found not only just before but also early after fertilization in developing seed endosperm, which might suggest the role of CKI1 also in a newly formed sporophytic tissue. Surprisingly, transcriptional activation of the paternally transmitted uidA gene under control of CKI1 promoter very early after fertilization suggests potential transcriptional activity of at least part of the male genome during early seed development in Arabidopsis.|