Molecular cloning and characterization of a proliferating cell nuclear antigen gene by chemically induced male sterility in wheat (Triticum aestivum L.).

Although a number of studies have shown that chemical hybridizing agents (CHAs) affect anther growth and regulate cell-cycle progression, little is known about the molecular and cellular mechanisms involved. Proliferating cell nuclear antigen (PCNA) is an essential factor in DNA replication, and in many other processes in eukaryotic cells. In this study, the open reading frame of TaPCNA, the PCNA in wheat (Triticum aestivum L.), was cloned by reverse transcription polymerase chain reaction (RT-PCR). Sequence analysis revealed that this gene was 792-bp long and encoded a protein with 234 amino acids. Alignment of the TaPCNA-predicted sequence revealed a high degree of identity with PCNAs from other plant species. A subcellular localization assay indicated that TaPCNA was localized in the nucleus. The TaPCNA was cloned into the prokaryotic expression plasmid pET32a, and the recombinant plasmid was transformed into BL21 (DE3). TaPCNA expression was induced by 0.5 mM isopropyl-beta-D-thiogalactopyranoside and verified using sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blot assays, which indicated that the fusion protein was successfully expressed. The gene involved in the G1-to-S transition, Histone H4, was downregulated by 1376- CIMS, which is a chemically induced male sterility line. However, a semi-quantitative RT-PCR revealed that TaPCNA expression was upregulated in 1376-CIMS. Our results suggest that CHAs (SQ-1) induce DNA damage in wheat anthers. DNA damage results in either the delay or arrest of cell-cycle progression, which affects anther development. This study will help to elucidate the mechanisms of SQ-1-induced male sterility.