Differential expression of SLOW WALKER2 homologue in ovules of female sterile mutant and fertile clone of Pinus tabulaeformis

Abstract

SLOW WALKER2 (SWA2) of Arabidopsis thaliana can cause suspending of nuclear division during mitosis of embryo sac development. In Pinus tabulaeformis, the free nucleus division of female gametophyte has similar suspension but the male gametophyte development is normal in female sterile mutant. A DNA fragment and an EST of the homologue in P. tabulaeformis were isolated by PCR. It is shown that the homologue gene has highest expression in vigorous division of free nucleus and lower expression in other stages during female gametophyte development of normal ovules by Real-time Quantitative PCR. The expression of the homologue in sterile ovules is lower than that in normal ovules in different stages of the process. Reverse transcription PCR shows a clear band in the free nucleus division and no band in cellularization of the normal ovules during female gametophyte development. However, there is no band appeared in the nucleus division and a clear band in cellularization of the sterile ovules. Cytological observation shows chromatin evenly distributed within free nuclei in normal female gametophyte condenses into unevenly lumps with dispersing degenerated DNA in cytoplasm of the sterile one. It is concluded P. tabulaeformis SWA2 homologue may undergo alternative splicing, involve in DNA binding/repairing and cell cycle progress during the free nucleus division of female gametophytes after dormancy.