Analysis of clock gene homologs using unifoliolates as target organs in soybean (Glycine max).

Soybean is a typical short-day crop, and its photoperiodic response of flowering is critical to its yield. This phenomenon was well studied during the last century, but the molecular mechanism governing it is unknown. The clock-gene homologs, GmLCL1 and GmLCL2 (Glycine max LHY/CCA1 Like 1 and 2) and GmTOC1 (Glycine max TOC1) were cloned from Glycine max L. KN18, and their expression patterns were analyzed using a system developed in this study. We employed 8h light/16h dark and 18h light/6h dark as short- and long-day conditions, respectively, because in these conditions soybean plants had significant indexes of flowering time. We also used unifoliolates, not the whole plant as Arabidopsis, as target organs for gene expression analysis. GmLCL1 and GmLCL2 had similar circadian expression patterns and both were morning genes, while GmTOC1 was an evening gene and peaked in the evening. The expressions of GmLCL1 and GmLCL2 were obviously antiphase to that of GmTOC1.Our study provided a system that simplified the experiments without compromising the quality of data obtained and was suitable for analyzing the molecular mechanism of flowering in soybean. GmLCL1, GmLCL2 and GmTOC1 may be the components of central clock in soybean.