Submitted to: PLoS One
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/2/2013
Publication Date: 1/21/2014
Publication URL: http://handle.nal.usda.gov/10113/60201
Citation: Wu, F., Price, B.W., Haider, W., Seufferheld, G., Nelson, R.L., Hanzawa, Y. 2014. Functional and evolutionary characterization of the CONSTANS gene family in short-day photoperiodic flowering in soybean. PLoS One. DOI:10.1371/journal.pone.0085754. Interpretive Summary: Through soybean domestication and many decades of scientific plant breeding that have selected for higher yield, the time of flowering in soybean has been shifted earlier. Understanding the processes controlling the time of flowering is one of the critical steps in our understanding of the factors affecting seed yield in soybean. CONSTANS (CO) is a protein that is known to affect the time of flowering in many different plants but little is known about its function in soybean. We report a comprehensive characterization of the CO gene family in soybean and the identification of two genes that may be key in the initiation of flowering in response to changes in day length. This information will be useful to scientists interested in the control of flowering.
Technical Abstract: CONSTANS (CO) plays a central role in photoperiodic flowering control of plants. However, much remains unknown about the function of the CO gene family in soybean and the molecular mechanisms underlying the short-day photoperiodic flowering of soybean. We identified 26 CO homologs (GmCOLs) in the soybean genome including many previously unreported genes. Phylogenic analysis classified GmCOLs into three clades conserved among flowering plants. Two homeologous pairs in Clade I, GmCOL1a/GmCOL1b and GmCOL2a/GmCOL2b, showed the highest sequence similarity to Arabidopsis CO. The mRNA abundance of GmCOL1a and GmCOL1b exhibited a strong diurnal rhythm under flowering-inductive short days with a peak at dawn, which coincided with the rise of GmFT2a and GmFT5a expression. In contrast, the mRNA abundance of GmCOL2a and GmCOL2b was extremely low. Our transgenic study demonstrated that GmCOL1a, GmCOL1b, GmCOL2a and GmCOL2b fully complemented the late flowering effect of the co-1 mutant in Arabidopsis. Together, these results indicate that GmCOL1a and GmCOL1b are potential inducers of flowering in soybean. Our data also indicate rapid regulatory divergence between GmCOL1a/GmCOL1b and GmCOL2a/GmCOL2b, while maintaining their protein function. Dynamic evolution of GmCOL regulatory mechanisms may underlie the evolution of the photoperiodic signaling in soybean.