Expression of flowering-time genes in soybean E1 near-isogenic lines under short and long day conditions

Abstract

Control of soybean flowering time is important for geographic adaptation and maximizing yield. Plant breeders have identified a series of genes (E genes) that condition time to flowering; however, the molecular basis in the control of flowering by these E genes, in conjunction with canonical flowering-time genes, has not been studied. Time to flowering in near-isogenic lines (NILs) at the E1 locus was tested using a reciprocal transfer experiment under short day (SD) and long day (LD) conditions. Beginning 8 days after planting, three plant samples were harvested every 3 h for a 48-h period. RNA was isolated from these plants, and RNA samples were pooled for each line and each time period for cDNA synthesis. RT-PCR analysis was performed using primers synthesized for a number of putative flowering-time genes based on homology of soybean EST and genomic sequences to Arabidopsis genes. The results of the reciprocal transfer experiment suggest that the pre-inductive photoperiod-sensitive phase of the E1 NILs responsible for inducing flowering is perceived as early as 5-7-day post-planting. No gene expression differences were found between the E1 and e1 NILs, suggesting that the E1 gene does not directly affect the flowering-time genes during the time period tested; however, differences were observed in gene expression between SD and LD treatments for the putative soybean TOC1, CO, and FT genes. The gene expression results in this study were similar to those of flowering-time genes found in other SD species, suggesting that the selected genes correspond to the soybean flowering-time orthologs.

Two Coordinately Regulated Homologs of FLOWERING LOCUS T Are Involved in the Control of Photoperiodic Flowering in Soybean

“…Some soybean cultivars can respond to photoperiod at the time the primary leaves are fully expanded (Borthwick and Parker, 1938;Thomas and Raper, 1984;Thakare et al, 2010). We analyzed the dynamics of GmFT2a and GmFT5a expression in Harosoy plants exposed to different durations of SD (12 h of light) after emergence followed by transfer to LD conditions (20 h of light).…”

Positional cloning and characterization reveal the molecular basis for soybean maturity locus E1 that regulates photoperiodic flowering

“…Although several genes, including the homologues of CO, displayed different expression patterns under long-and short-day conditions, they did not differ noticeably in their expression patterns between the E1 NILs (39,40), except that the abundance of GmFT transcripts was negatively correlated with flowering time under long-day conditions (40). The regulatory network controlling photoperiod response and flowering time through photoreceptor genes (E3, E4) and GmFT genes in soybean therefore remains largely unknown because of the lack of understanding of the key gene at the E1 locus.…”

“…Thakare et al compared the transcriptional profiles of homologues of Arabidopsis flowering-time genes between soybean nearisogenic lines (NILs) harboring contrasting E1 alleles (39). Although several genes, including the homologues of CO, displayed different expression patterns under long-and short-day conditions, they did not differ noticeably in their expression patterns between the E1 NILs (39,40), except that the abundance of GmFT transcripts was negatively correlated with flowering time under long-day conditions (40).…”

Inheritance of late flowering in natural variants of soybean cultivars under short-day conditions

“…0635 (p=0.80-0.70) and 26.005 (p=0.20-0.10) (Table 3). These results suggest that the difference in days to flowering between São Carlos and 'Davis' depended mainly on genetic differences instead of on environmental errors (Thakare et al, 2010); in addition, the genetic rates indicate that the São Carlos variant most likely differs from the Davis cultivar by one mutation in a pair of recessive alleles and in one gene locus.…”

“…This wide adaptability is most likely associated with the genetic diversity of the plant (Liu et al, 2008(Liu et al, , 2009 cultivars. These mutations may represent an important source of genes for the development of soybean cultivars adapted to different low-latitude regions or sowing periods in breeding programs (Thakare et al, 2010;Watanabe et al, 2012). The genetic control of flowering time under short-day conditions is determined by a genetic system that is different and independent from the one that determines flowering under long-day conditions.…”