A CIB1-LIKE transcription factor GmCIL10 from soybean positively regulates plant flowering

CRYPTOCHROME-INTERACTING basic helix-loop-helix 1 (CIB1) is a well characterized transcriptional factor which promotes flowering through the physical interaction with the blue light receptor CRYPTOCHROME 2 (CRY2) in Arabidopsis. However, the role of its counterpart in crop species remains largely unknown. Here, we describe the isolation and characterization of a CIB1 homolog gene, Glycine max CIB1-LIKE10 (GmCIL10), from soybean genome. The mRNA expression of GmCIL10 in the unifoliate leaves shows a diunal rhythm in both long day (LD) and short day (SD) photoperiod, but it only oscillates with a circadian rhythm when the soybean is grown under LDs, indicating that the clock regulation of GmCIL10 transcription is LD photoperiod-dependent. Moreover, its mRNA expression varies in different tissue or organs, influenced by the develpomental stage, implying that GmCIL10 may be involved in the regulation of multiple developmental processes. Similar to CIB1, GmCIL10 was evident to be a nuclei protein and ectopically expression of GmCIL10 in transgenic Arabidopsis accelerates flowering under both LDs and SDs, implying that CIBs dependent regulation of flowering time is an evolutionarily conserved mechanism in different plant species.