Abstract：Photoperiod plays an important role in triggering the change from vegetative growth to reproductive growth. CO (constans) plays a significant role in the photoperiod pathway in the model plant Arabidopsis. To learn more about the CO-like gene in wheat, the homologous cloning method was used to isolate the related gene. Here a novel gene TaCO9-1A (GenBank accession: KM236233) that encoding a CO-like protein was cloned from hexaploid wheat (Triticum aestivum L.) Ningchun 4. The results showed that the coding sequences (CDS) of TaCO9-1A was 876 bp in length, encoding 291 amino acids including a classic CCT domain, but not the B-box domain. A phylogenetic analysis showed that TaCO9-1A was classified into the same branch with Ghd7 in rice (Oryza sativa L.) and HvCO9 in barely (Hordeum vulgare L.), which were negative regulators of flowering. TaCO9-1A protein with a predicted molecular weight 31 kD was succesfully expressed by the plasmid pEASYE1-TaCO9-1A in Escherichia coli BL21 (DE3). The expressions of TaCO9-1A were detected in root, stem, leaf and young spike in common wheat at heading stage by Real-time quantitative PCR (qRT-PCR), and the expression level was highest in leaf and lowest in root. Comparing the sequence of TaCO9-1A in winter and spring varieties, it was found that 6 bp deletion in the second exon existed in winter varieties. Thus, a codominant marker was developed based on the 6 bp deletion of TaCO9-1A in winter varieties. In 25 wheat varieties with different winter and spring habits, two kinds of bands (511 and 517 bp) were amplified with this marker. The codominant marker was highly correlated with not only spring and winter habit but also the heading, flowering time of wheat cultivated at Yangling in two years. Our results revealed that TaCO9-1A played an important role in wheat vernalization and photoperiod pathway. These results provide basic data for the further research of TaCO9-1A regulating development in wheat, and will help to reveal the molecular mechanism of spring-winter habit and maturity traits in wheat by TaCO9-1A regulation.
