Functional Study Of Sister Chromatid Cohesion Factor CHROMOSOME TRANSMISSION FIDELITY 18 During Female Gametophyte Development In Arabidopsis

The female gametophyte is a key structure during sexual reproduction in angiosperms.Female gametophyte development is a well-defined and successive program in Arabidopsis thaliana.It was divided into two stages and contains many complicate biological processes.In recent years,advanced Molecular biology studies have led to important progress in the field of plant gametophyte developmentIn most sexually reproducing plants,a single somatic,sub-epidermal cell in an ovule is selected to differentiate into a megaspore mother cell(MMC),which is committed to giving rise to the female germline.However,it remains unclear how intercellular signaling among somatic cells define only one cell in the sub-epidermal layer to differentiate into the MMC;how the function megaspore(FM)is selected and transferred to mitosis;what the relationship between female gametophyte and surrounding tissue in the process of ovule development is.In this project,we aim to reveal the function of CHROMOSOME TRANSMISSION FIDELITY 18(CTF18)in Arabidopsis thaliana female gametophyte development.In this study,we use a T-DNA insertion mutant of ctf18 as the research material.By analyzing phenotypic and functional response experiment,we confirmed that CTF18 is involved in the regulation of female gametophyte development in Arabidopsis thaliana.In ctf18 mutant plant,the FM exhibits disturbed mitotic progression.Through in situ hybridization and GUS protein fusion expression analysis,we found that CTF18 displays a dynamic expression pattern during ovule development.At MMC stage,CTF18 is expressed in nucellus and integuments.During megagametogenesis,CTF18 is detected in developing embryo sac.In mature ovule,CTF18 signal is only enriched in the micropylar pole of the integuments.During megasporogenesis,pDMC1::GFP and pSPL::GUS markers are normally expressed in ctf18 ovules,suggesting that CTF18 may not play a role during megasporogenesis.In addtion,we also performed the transparent observation analysis and applied the pAKV::YFP maker line to study the effects of CTF18 on megagametogenesis.The result showed that FM mitosis was disordered,with female gametophyte development arrested at FG1,FG2 and FG4 stage,indicating that CTF 18 plays an important role in regulating female gamete development in Arabidopsis thaliana.Previously study showed that CTF 18 was involved in DNA replication by interact with RFC family protein.DNA replication is the precondition of cell division and growth.We thus hypothesized that CTF 18 may participate in regulating cell division or expansion.In WT plants,development of embryo sac and integument was synchronized.Along with the enlargement of embryo sac,integument is organized at the same time to wrap the embryo sac tightly.At stage FG7 the integument envelops the embryo sac,only leaving a small opening,the micropyle.Whereas,ctf18 ovule displayed short integument phenotype with protruding embryo sac.Statistical analysis of the cell length showed that the out integument cell elongation was restrained in ctf18 mutant ovule micropyle.Our results indicate that CTF18 is required for promoting integument cells expansion in the process of female gametophyte development,which determines ovule patterning.Comparative ovule transcriptome analysis showed that CTF18 regulates female gametophyte development likely through controlling reproductive development and floral development gene.expression.In conclusion,CTF18 exhibits a dynamic spatio-temporal expression patterns during Arabidopsis thaliana ovule development,and plays an important role during ovule development by promoting function megaspore mitosis and integument cells expansion.