Isolation and characterization of a wheat F8-1 homolog required for physiological male sterility induced by a chemical hybridizing agent (CHA) SQ-1

We investigated the relationship between a pollen-specific protein homolog and pollen abortion in an SQ-1-induced male sterile line of wheat (Triticum aestivum L.). We previously determined that EST S414 (Ta20678) was obviously down-regulated in a line of Xinong 1376 wheat in which male sterility was induced by SQ-1 (a chemical hybridizing agent). In the present study, we obtained the full sequence of F8-1 from wheat. The open reading frame sequence of the F8-1 gene was 495 bp, encoding 165 amino acid residues with a predicted molecular weight of 18.2759 kDa and an isoelectric point of 4.86. This sequence was identified as a Secale cereale × Triticum durum F8-4 homolog with 100 % identity. The amino acids represent a conserved domain in pollen Ole e I that contains the consensus sequence Q-G-R-V-Y-C-D-T-C-R. The protein has a close evolutionary relationship with orthologs in S. cereale × T. durum and Triticum urartu, consisting of 9.09 % alpha helix, 24.85 % extended strand, and 66.06 % random coil. F8-1 was only expressed in anthers during the binucleate and trinucleate stages and expression gradually decreased from the binucleate stage to the trinucleate stage. The expression of F8-1 gene of physiological male sterility 1376 (PHYMS-1376) was lower than that of 1376 at both the binucleate and trinucleate stages. Subcellular localization showed that the F8-1 protein was expressed at the nucleus. RNAi tests showed that down-regulation of the F8-1 was associated with an increase in the percentage of pollen abortion. Therefore, F8-1 is a positive regulator of physiological male sterility.