The novel function of the Ph1 gene to differentiate homologs from homoeologs evolved in Triticum turgidum ssp. dicoccoides via a dramatic meiosis-specific increase in the expression of the 5B copy of the C-Ph1 gene
The Ph1 gene is the principal regulator of homoeologous chromosome pairing control (HECP) that ensures the diploid-like meiotic chromosome pairing behavior of polyploid wheat. The HECP control was speculated to have evolved after the first event of polyploidization. With the objective to accurately understand the evolution of the HECP control, wild emmer wheat accessions previously known to differ for HECP control were characterized for the structure and expression of the candidate Ph1 gene, C-Ph1. The C-TdPh1-5A and 5B gene copies of emmer wheat showed 98 and 99% DNA sequence similarity respectively with the corresponding hexaploid wheat copies. Further, the C-TdPh1-5B carried the C-Ph1-5B specific structural changes and transcribed three splice variants as observed in the hexaploid wheat. Further, single nucleotide changes differentiating accessions varying for HECP control were identified. Analyzed by quantitative expression analysis, the wild emmer accessions with HECP control showed ~ 10,000-fold higher transcript abundance of the C-TdPh1-5B copy during prophase-I compared to accessions lacking the control. Differential transcriptional regulation of C-TdPh1-5B splice variants further revealed that C-Ph1-5Balt1 variant is mainly responsible for differential accumulation of C-Ph1-5B copy in accessions with HECP control. Taken together, these results showed that the HECP control evolved via transcriptional regulation of splice variants during meiosis.
KeywordsPh1 gene Homoeologous chromosome pairing control Meiosis Gene expression
We would like to thank Dr. Moshe Feldman for kindly sharing the germplasm.
KS and KSG designed the research. KS and MAK performed the experiments and data analysis. KS and KSG wrote the manuscript. KS, MAK, and KSG critically revised the manuscript.
This work was supported by USDA National Institute of Food and Agriculture (Hatch project number WNP00449) and United States Agency for International Development Feed the Future Innovation Lab-Climate Resilient Wheat (Grant number AID-OAA-A-13-00008).
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
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