Charecterization of the PHERES1 Orthologs in the Apomict Boechera

Abstract

ABSTRACTHere we report the structure and expression patterns of orthologs for PHERES1 (PHE1) gene in the apomict Boechera holboellii. The PHE1 cDNAs were obtained by RT-PCR from Boechera anthers and carpels before and after fertilization. PHE1 encodes a type 1 MADS box protein and promotes seed growth. Also, PHE1 shows monoallelic expression and is the only plant gene known to be paternally express and maternally silenced imprinted gene. In Arabidopsis, PHE1 is repressed by the FERTILIZATION INDEPENDENT SEED (FIS) complex, also known as the Polycomb group complex 2. The FIS complex represses endosperm development in Arabidopsis thaliana prior to fertilization and plays an important role in regulating the development of endosperm following fertilisation. However, it is not known how apomicts have adjusted endosperm development to deal with parental genome imbalance due to non-reduction of maternal gametes. Therefore, the triploid apomictic Boechera species, as a close relative of A. thaliana, provide an attractive opportunity to investigate PHE1 function in pseudogamous apomicts. The 310 bp cDNA fragment of Boechera PHE1 transcript showed homology with AtPHE1. Phylogenetic analyses revealed that Boechera PHE1 is closely related to A. thaliana. The expression patterns of PHE1 in natural apomict Boechera during seed development were also revealed that the maternal BhPHE1 allele is also expressed before fertilization in carpels.