Poster: Reproductive Development

Abs # 481: The putative sensor histidine kinase CKI1 is involved in Arabidopsis female gametophyte development

Presenter:	Hejatko, Jan , hejatko@sci.muni.cz
Authors	Hejatko, Jan  (A) (B)  Pernisova, Marketa  (B)   Eneva, Tinka  (D)   Palme, Klaus  (D) (C)  Brzobohaty, Bretislav  (A) (B)
Affiliations:	(A): Institute of Biophysics, Czech Academy of Sciences (B): Masaryk University, Dept. of Functional Genomics and Proteomics, Laboratory of Plant Molecular Physiology (C): Max-Delbrück-Laboratorium in der Max-Planck-Gesellschaft (D): Institut für Biologie II, Albert-Ludwigs-Universität Freiburg

Embryo sac formation is a fundamental step in plant sexual reproduction. However, the key players driving female gametophyte development remain elusive. Here we present data indicating that a two-component sensor histidine kinase CKI1 is required for completion of megagametogenesis in Arabidopsis. We isolated a recessive loss-of-function mutation in CKI1 resulting from an insertion of En-1 transposon into the CKI1 coding sequence. The mutant cki1-i allele could not be transmitted through the female germ line and conferred partial lethality on the male gametophyte. Confocal microscopy identified a block in megagametogenesis characterised by the abortion of the central vacuole in mutant embryo sacs and degradation of the developing female gametophyte after completion of all mitotic divisions. Two independent stable alleles and one revertant wild type allele resulting from En-1 excision confirmed a causal link between the cki1-i and the phenotype. In situ mRNA localisation and histochemical analysis of stable transformants harbouring uidA gene under the control of CKI1 promoter revealed the expression of CKI1 in both the tapetum and in the developing embryo sacs throughout megagametogenesis and early after fertilization. The results provide evidence that gametophytic expression of the gene for two-component sensor histidine kinase CKI1 is essential for specific processes during megagametogenesis. Further, the identified transient endosperm-specific activation of male-inherited CKI1 promoter very early after fertilization suggest a need to reconsider the concept of genome-wide male imprinting during early seed development. Supported by grants nos. VS96096, MSM143100008 and LN00A081, the DFG, European Communities Biotech Program (QLRT-2000-0020, QLK5-CT-2001-01871) and DAAD.