Cloning and characterization of the homoeologous genes for the Rec8-like meiotic cohesin in polyploid wheat

Authors: MA, GUOJIA - North Dakota State University; ZHANG, WEI - North Dakota State University; LIU, LIWANG - North Dakota State University; Chao, Wun; Gu, Yong; Qi, Lili; Xu, Steven; CAI, XIWEN - North Dakota State University

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2018
Publication Date: 10/11/2018
Citation: Ma, G., Zhang, W., Liu, L., Chao, W.S., Gu, Y.Q., Qi, L., Xu, S.S., Cai, X. 2018. Cloning and characterization of the homoeologous genes for the Rec8-like meiotic cohesin in polyploid wheat. Biomed Central (BMC) Plant Biology. 18:224. https://doi.org/10.1186/s12870-018-1442-y.
DOI: https://doi.org/10.1186/s12870-018-1442-y

Interpretive Summary: Meiosis is a specialized cell division to generate gametes (i.e. eggs and sperms) involved in the sexual reproduction. Meiosis includes two successive nuclear divisions. The first meiotic division involves pairing and segregation of homologous (identical) chromosomes and reduces the number of chromosomes in half. The second meiotic division involves separation of two daughter strands of chromosomes and formation of four daughter cells which subsequently develop to gametes. During the meiotic cell division, a cohesion protein complex, known as Rec8 cohesin, involves in the coordination of chromosome segregation. The genes encoding Rec8 cohesin have been cloned and characterized in a number of diploid plant species (containing one genome) such as Arabidopsis (mouse ear cress weed), maize, and rice. However, knowledge of the genes for Rec8 cohesin is very limited in polyploid plants (containing more than one genome). Modern wheat crop is a polyploid species which contains three genetically-related genomes A, B, and D. Here, we report the cloning of the six genes for Rec8 cohesin located in A, B, and D genomes of tetraploid durum wheat, hexaploid bread wheat, and diploid D-genome donor species Aegilops tauschii. The coding DNA sequences of the six genes are all 1,827 base pairs of nucleic acids in length, encoding 608 amino acids. They differ from each other primarily in noncoding sections. The gene expression analysis indicated that the genes from the A and D genomes express dominantly over the one from the B genome for Rec8 cohesin production in polyploid wheat. The differential expression and structure of the genes for Rec8 cohesin in different genomes imply a distinct origin and evolutionary route of the wheat B genome from the A and D genomes.

Technical Abstract: The meiotic cohesin Rec8 is a cohesion protein involved in the coordination of meiotic chromosome segregation. Here, we report the cloning and characterization of the Rec8 homoeoalleles in polyploid wheat. Two Rec8 homoeoalleles from tetraploid wheat (TtRec8-A1 and TtRec8-B1) and one from hexaploid wheat (TaRec8-D1) were cloned and characterized using the comparative genomics and subcellular techniques. The other two Rec8 homoeoalleles in hexaploid wheat (TaRec8-A1 and TaRec8-B1) and the one in Aegilops tauschii (AetRec8-D1) were identified from their reference genome sequences and transcriptomes. The coding DNA sequences (CDS) of these six Rec8 homoeoalleles are all 1,827 bp in length, encoding 608 amino acids. They differ from each other primarily in introns although single nucleotide polymorphisms exist in CDS. TtRec8-A1 expressed dominantly over TtRec8-B1, but comparably to TaRec8-D1 in the tetraploid wheat background. A similar expression pattern was observed with these Rec8 homoeoalleles when the D subgenome was present. Therefore, the homoeoalleles from the subgenomes A and D express dominantly over the one from the subgenome B for Rec8 cohesin production in polyploid wheat. The differential expression and structure of the wheat Rec8 homoeoalleles imply a distinct origin and evolutionary route of the wheat B subgenome from the A and D subgenomes